Article

What roundabout design provides the highest possible safety?

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... The number of injured has even a quadratic relationship with the speeds. Furthermore a positive relationship was measured between traffic volume and the number of crashes (Brüde & Larsson, 2000). ...
... For the severest crashes, those with fatal and serious injuries (i.e. a hospitalisation of at least 24 hours) the results were even worse (best estimate of the increase of 41-46%). The results were unexpected, although earlier findings suggested possible specific safety problems for bicyclists at roundabouts (see for example Brilon, 1997;Brüde and Larsson, 2000;Layfield and Maycock, 1986;Schoon and van Minnen, 1993). ...
... In a Swedish cross-sectional study it was concluded that the bicyclist crash rate at roundabouts with cycle crossings (i.e. roundabouts with a cycle path design) was lower compared to roundabouts with bicyclists riding on the carriageway (Brüde and Larsson, 2000). ...
... For the severest crashes, those with fatal and serious injuries (i.e. a hospitalisation of at least 24 hours) the results were even worse (best estimate of the increase of 41-46%). The results were unexpected, although earlier findings suggested possible specific safety problems for bicyclists at roundabouts (see for example Brilon, 1997;Brüde and Larsson, 2000;Layfield and Maycock, 1986;Schoon and van Minnen, 1993). ...
... In a Swedish study it was concluded that the bicyclist crash rate at roundabouts with cycle crossings (i.e. roundabouts with a cycle path design) was lower compared to roundabouts with bicyclists riding on the carriageway (Brüde and Larsson, 2000). ...
... Earlier findings (Brüde and Larsson, 2000) suggested a weaker result for two-lane roundabouts compared to single-lanes. Our study cannot confirm nor deny this result. ...
Article
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Roundabouts in general have a favourable effect on traffic safety, at least for crashes causing injuries. A meta-analysis on 28 studies in 8 different countries revealed a best estimate of a reduction of injury crashes of 30-50%. Other studies delivered similar results. All those studies reported a considerably stronger decrease in the number of severest crashes (fatalities and crashes involving serious injuries) compared to the decrease of the total number of injury crashes. Less is known about the safety effects of roundabouts for particular types of road users, such as bicyclists. Roundabouts seem to induce a higher number of bicyclist-involved crashes than might be expected from the presence of bicycles in overall traffic. In Flanders-Belgium bicyclists appear to be involved in almost one third of reported injury crashes at roundabouts while generally only 14.6% of all trips (5.7% of distances) are made by bicycle. The apparent overrepresentation of bicyclists in crashes at roundabouts was the main cause to conduct an evaluation study on the effects of roundabouts, more specifically on crashes involving bicyclists.
... Leaf and Preusser [3] have shown that vehicle speed has a significant impact on pedestrian injuries during accidents. Based on the research conducted in Sweden [4], the main factors affecting the safety of the roundabout are the number of roads at the roundabout, the diameter of the island, and the speed and intensity of traffic. The study authors argue that single-line roundabouts are the safest and building roundabouts with a large radius is associated with higher permissible speeds, which can increase the number of accidents. ...
... Brake ratios were determined, the distance between vehicles (values 1-4 in Figs. 4,5) and the probability of pedestrian entry on the road strips (values 0, 0.5, 1 in Figs. 4,5) were changed. ...
... 4,5) and the probability of pedestrian entry on the road strips (values 0, 0.5, 1 in Figs. 4,5) were changed. Figure 4 shows that the speed of vehicles and pedestrians affects the number of vehicles slipping and the number of collisions. ...
Conference Paper
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The paper presents an analysis of the impact of road conditions, the distance between vehicles and the number of pedestrians on the roundabout capacity. The study was based on a developed cellular automaton (CA) model and the implemented simulation system. The developed CA model extends the basic traffic model with a braking mechanism. It also reflects the actual technical conditions of vehicles (acceleration and braking depending on the dimensions and functions of the vehicle, as well as the driving at a roundabout of different speeds that are appropriate for the size of the vehicle). The study was based on the example of a two-lane roundabout with four two-lane inlet roads.
... A consistent finding of these studies is that motorized vehicle traffic volume is a major factor in bicycle accident frequency. Further, an inverse relation of the central island radius to bicycle accident occurrence when radii are 10-20 m and a positive relation for larger radii was reported repeatedly [4,18]. This goes together with observed adverse effects of the presence of central island aprons that are traversable for motorized vehicles and the apron's width, respectively [15,16]. ...
... Further, central islands which are elevated >2 m seem to improve the bicycle safety performance of roundabouts [4]. A relation of the number of legs to bicycle accident occurrence could not be established firmly [14][15][16]18]. The same is true for the number of lanes on the circulatory roadway or its width [16][17][18]. ...
... A relation of the number of legs to bicycle accident occurrence could not be established firmly [14][15][16]18]. The same is true for the number of lanes on the circulatory roadway or its width [16][17][18]. However, the results from different studies are not easily compared to each other, due to differences in methodologies. ...
Article
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The positive effects of active mobility on mental and physical health as well as on air quality are widely acknowledged. Increasing the share of active travel is therefore an aim in many countries. Providing bicycle-safe infrastructure is one way to promote cycling. Roundabouts are a common traffic infrastructure and are supposed to facilitate safe and smooth traffic flow. However, data on road traffic accidents indicate an over-proportional involvement of cyclists in accidents at roundabouts. In the present study, the influence of roundabout geometry and traffic flow on bicycle accident occurrence was investigated using a logistic regression approach on twelve parameters of N = 294 mostly small- and mini-sized single-lane roundabouts in the Canton of Berne, Switzerland. Average weekday motorized traffic was identified as a major factor in explaining bicycle accident occurrence at roundabouts. Further, the radius of the central island, the location of the roundabout (in town vs. out of town) and the number of legs were significantly related to bicycle accident occurrence. While these results are in general agreement with findings from similar studies, the findings regarding the central island’s radius and the number of legs underpin the need for roundabout type-specific studies: Some parameters may not prove relevant in intermediate- to large-sized roundabouts, but become critical in small or mini roundabouts, which are common in Switzerland and numerous in the present sample.
... When collisions do occur, the reduced speed differential between vehicle and cyclist reduces the severity of the collisions and probability of severe injury and death (Leaf & Preusser, 1999). A variety of traffic calming design measures, use of bicycle boulevards, and construction of roundabouts can decrease motor-vehicle speeds (Brude & Larsson, 2000). ...
... While roundabouts with one lane and mixed traffic or a separated facility may offer safety benefits to cyclists compared to signalized intersections, those with bike lanes inside the intersection or with more than one travel lane carried through appear to increase crash risk. Daniels, Nuyts, and Wets (2008), found a statistically significant higher risk of injury crashes after conversion to roundabouts; Schoon and van Minnen (1994) found a reduction in bicyclist crash rate for single-lane roundabouts; Brude and Larsson (2000) found multilane roundabouts to be associated with about twice the crash risk and injury risk; Daniels, Brijs, Nuyts, and Wets (2009) found a statistically significant higher risk of bicycle injury crashes after conversion from "conventional" intersections to roundabouts constructed with bicycle lanes; and Brude and Larsson (2000) found roundabouts with separated bicycle facilities to be associated with about half the crash risk as "conventional" intersections. ...
... While roundabouts with one lane and mixed traffic or a separated facility may offer safety benefits to cyclists compared to signalized intersections, those with bike lanes inside the intersection or with more than one travel lane carried through appear to increase crash risk. Daniels, Nuyts, and Wets (2008), found a statistically significant higher risk of injury crashes after conversion to roundabouts; Schoon and van Minnen (1994) found a reduction in bicyclist crash rate for single-lane roundabouts; Brude and Larsson (2000) found multilane roundabouts to be associated with about twice the crash risk and injury risk; Daniels, Brijs, Nuyts, and Wets (2009) found a statistically significant higher risk of bicycle injury crashes after conversion from "conventional" intersections to roundabouts constructed with bicycle lanes; and Brude and Larsson (2000) found roundabouts with separated bicycle facilities to be associated with about half the crash risk as "conventional" intersections. ...
Article
Problem and method: This paper takes a critical look at the present state of bicycle infrastructure treatment safety research, highlighting data needs. Safety literature relating to 22 bicycle treatments is examined, including findings, study methodologies, and data sources used in the studies. Some preliminary conclusions related to research efficacy are drawn from the available data and findings in the research. Results and discussion: While the current body of bicycle safety literature points toward some defensible conclusions regarding the safety and effectiveness of certain bicycle treatments, such as bike lanes and removal of on-street parking, the vast majority treatments are still in need of rigorous research. Fundamental questions arise regarding appropriate exposure measures, crash measures, and crash data sources. Practical applications: This research will aid transportation departments with regard to decisions about bicycle infrastructure and guide future research efforts toward understanding safety impacts of bicycle infrastructure.
... For 'other' and pedestrian crashes, no non-flow variables included in the analysis were significant. (2000) -Sweden Brude and Larsson (2000) surveyed 650 of Sweden's approximately 700 roundabouts and classified them with respect to geometric design, speed and a number of other factors. Crash data was then collected as well as the number of vehicles, cyclists and pedestrians passing through the roundabouts for a number of sites. ...
... Arndt (1998) found that multiple entry lanes increased the number of rear-end crashes, and multiple circulating lanes increased the number of entering v circulating crashes. This is consistent with Brude and Larsson (2000), who found that multi-lane roundabouts had higher crash rates for motorists, cyclists and pedestrians. The only study where the opposite relationship was observed was that of Harper (2005), who found that approaches with multiple entry lanes had lower entering v circulating crash rates. ...
... He found that increasing 85th percentile speeds resulted in more crashes for nearly all crash types and also that a change in 85th percentile speed between geometric elements resulted in more singlevehicle crashes. Brude and Larsson (2000) found that speed was directly proportional to crashes and that speeds were higher when the general speed limit was higher than the local limit, where the roundabout had multiple lanes and where the radius of the central island was 10-20m. They also found that where the radius of the central island was smaller than 10m, speeds were higher. ...
Technical Report
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The management of speed is considered an important safety issue at roundabouts. The approach speed and negotiating speed through roundabouts depends on the geometric design of the roundabout and sight distance. In New Zealand and in Australia, the design standards recommend long approach sight distances and provision of relatively high design speeds. This is in contrast to European roundabouts, where visibility is normally restricted and the geometric design encourages slow approach and negotiation speeds. This work, undertaken in 2006, extends previous research by the authors developing crash prediction models at roundabouts to include sight distance, intersection layout and observed speed variables. Models have been produced for the major motor vehicles only, pedestrian versus motor vehicles and cyclists versus motor vehicle crash types. Flow-only models have also been produced for roundabouts on roads with high speed limits. The models produced indicate that roundabouts with lower speeds (observed and speed limit), fewer approach lanes and reduced visibility have lower crash rates.
... For the single-vehicle crashes, however, the coefficient for the ADT is well below 1, suggesting that the average number of single-vehicle crashes per passing vehicle is lower on busier roundabouts. In existing research, ADT-parameters below as well as above 1 for crashes at roundabouts were found (Brüde and Larsson, 2000;Maycock and Hall, 1984). ...
... In the previous paper, we mentioned that the number of lanes in existing research showed some tendencies to be relevant (Brüde and Larsson, 2000;Daniels et al., 2009;Persaud et al., 2001). But we argued as well that the number of lanes could act as a proxy for traffic volume in those studies. ...
Article
This paper builds upon the results of previously developed crash prediction models for roundabouts. The originally investigated sample was extended from 90 to 148 roundabouts. Poisson and gamma modelling techniques were used, the latter ones since underdispersion in the crash data was observed. Separate models were fit for crashes with six different types of road users: bicyclists, motorcyclists, passenger and heavy four-wheel vehicles, moped riders and pedestrians. A further distinction was made between single-vehicle and multiple-vehicle crashes.The results show that the overall number of crashes is more or less proportional to the number of motorized vehicles. The mean number of single-vehicle crashes per passing vehicle is lower on busier roundabouts. Confirmation is found for the existence of a ‘safety-in-numbers’ effect for different types of road users. Three-leg roundabouts tend to perform worse than roundabouts with four or more legs. More crashes seem to occur at roundabouts with bypasses for traffic in some direction. Larger central islands correlate with more single-vehicle crashes. Moped riders and motorcyclists are strongly overrepresented in both single-vehicle and multiple-vehicle crashes whereas bicyclists are clearly overrepresented in multiple-vehicle crashes. Roundabouts with cycle paths perform better than roundabouts with other types of cycle facilities, particularly in comparison with roundabouts with cycle lanes close to the roadway.
... It must be said that crash reductions are most pronounced for motor vehicle, less pronounced for pedestrians (30-40 percent reduction), bicyclists (10 percent) and motorcyclists, depending on the study and design treatments [5,7,9,14]. Evaluation studies based on crash, traffic and geometric data also showed variation in crash rates at roundabouts, or particular groups of roundabouts, mainly driven by traffic exposure [13,15]. The results of statistical crash data analysis in different countries where the roundabouts are in operation by time, particularized for individual crash categories, are reported in several studies to which it refers. ...
... A better understanding of the safety effects of geometric design elements and traffic exposure can assist designers in optimizing the safety of all users [5]. According to [6,8,12,15,16], Table 2 summarizes elements or measures with a significant relationship with crash frequency at roundabouts for some crash categories. In particular, the entry deflection forces all vehicles to slow down, reducing the probability of crash and its severity (see Figure 3). ...
... Leaf and Preusser [7] found vehicle velocity has a tremendous effect on the scale of injuries sustained by a pedestrian hit by a vehicle: slowing down from 48 km/h to 32 km/h means the pedestrian's chances of surviving increase ninefold. In a study in Sweden [8], major factors of roundabout safety were specified: the number of lanes in a roundabout, island diameter, and also traffic speed and intensity. The authors of the study argued that single-lane roundabouts are the safest, whereas large-radius roundabouts result in a higher permissible speed, which is positively related to the number of accidents. ...
... The roundabout island diameter amounted to 56 m. The roundabout capacity was examined on the sample of 500 vehicles, by measuring the number of iterations needed for moving all the vehicles through the roundabout, and using the formula: b = n vehicles n iterations (8) where b is roundabout capacity, n vehicles is the number of vehicles that have driven across the roundabout (500), and n iterations is the number of CA iterations. The simulation was repeated 1000 times in order to obtain results that are not distorted by random events. ...
Article
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The current article presents a roundabout traffic model based on cellular automata for computer simulation. The model takes into account various sizes of roundabouts, as well as various types and maximum speeds of vehicles. A realistic vehicle braking phase is presented which is adjusted to the kind of vehicle and weather conditions. It also analyses roundabout traffic options including where the various rules for entering and exiting a roundabout apply. Traffic rules are contained in respective traffic scenarios. The simulation results indicate that there is significant scope for roundabout traffic reorganisation, with a mind to increasing roundabout capacity.
... Rodegerdts 2000) also describes several roundabout safety models that may be applied to the United States, including the Maycock and Hall model developed based on data from UK roundabouts (Maycock and Hall 1984); FHWA's four leg roundabout crash prediction models for America; Arndt's model for Australia (Arndt and Troutbeck 1998); Brude and Larsson's Swedish model (Brude 2000); and Guichet's French model. These models can be used to predict the general number of accidents at roundabouts (Guichet 1997). ...
... Multilane roundabouts have more cyclist accidents (six times) than single lane roundabouts, although this was likely due to the volume difference. They also found that central island diameters greater than 10 meters were safer than those smaller than 10 meters (Brude 2000). ...
Article
This research was focused on two issues related to multilane roundabouts on high-speed highways (speed limit 45 mph or greater) in rural and suburban areas. The first was the tradeoff between converting a traditional stop-controlled or signalized intersection to a multilane roundabout while the second was the safety of newly constructed high-speed multilane roundabouts in rural and suburban areas. The research team reviewed information from diverse published documents and conducted a survey of state and local transportation agencies. Crash data on multilane rural roundabouts were not available for this research. Therefore, the research team relied on crash and other data for single lane roundabouts that were constructed to replace rural two-way stop-controlled intersections in Kansas. To gain further insights into the safety of rural multilane roundabouts, the research team focused on investigating the safety of urban multilane roundabouts from published sources. Results of the survey indicated the need for proper design of roundabouts including signage and lighting and the potential for gaining benefits from public informational campaigns. Results of the Kansas data analysis of single lane roundabouts showed that overall all types of crashes were reduced after conversion of TWSC intersections to modern single lane roundabouts. Total crashes decreased by 58.13%; fatal crashes were reduced by 100% at all locations and non-fatal injury crashes were reduced with an overall reduction rate of 76.47%. Property-damage-only crashes were reduced by 35.49% as a whole, but two out of the four analyzed sites experienced increases in property-damage-only crashes after conversion to roundabouts. The annual value of the reduction in comprehensive crash costs from conversion of a two-way stop-controlled intersection on a rural, high-speed highway to a single lane modern roundabout was between $1.0 million and $1.6 million in 2014 dollars. A review of multilane roundabout conversions (mostly in urban areas) showed safety improvements compared to signalized and two-way stop-controlled intersections. Recommendations are presented in the report.
... A better understanding of effects on the safety by the various geometric design elements and traffic exposure can assist the designer in optimizing the safety of all users. According to [5,8,[16][17][18][19][20], Table 2 summarizes measures with a significant relationship with crash frequency at roundabouts for some crash categories: single vehicle (sv); crash between an entering and a circulating vehicle (e/c); rear-end crash on the approach (re); pedestrian (p); crash between an exiting and a circulating vehicle at multilane roundabouts (exit/c). In particular, the entry deflection forces all vehicles to slow down, reducing the probability of a crash and the severity of a crash (see Figure 3). ...
Conference Paper
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Pedestrians are important users of the transportation system, but most guidelines have given them little importance in the geometric design of roads and intersections. In these cases it can be difficult for vehicles and pedestrians to share the road safely, particularly at intersections where vehicle-pedestrian conflicts (and the risk of vehicle–pedestrian crashes) can be a frequently recurring situation even with low pedestrian volume. In a sustainable safety vision road system planning and design must include engineering choices that help to improve the sharing of road space between vehicles and pedestrians, as well as for other vulnerable users. It is known that modern roundabouts are safer than other intersection forms both for effects on speeds and for effects on conflicts between road users; several road authorities, indeed, have foreseen to convert specific types of intersections into roundabouts. Summarizing international experience with roundabouts and pedestrians, the paper provides a review of the existing literature dealing with pedestrian safety and accessibility issues at roundabouts. First, safety aspects at modern roundabouts are presented, followed by a brief explanation of the effects of roundabouts on pedestrian safety documented in the scientific literature. At last, this research provides an overview of the current state of practice and implications in the roundabout design to maximize their potential with regard to safety pedestrians. Keywords: road safety, pedestrian safety, roundabout. 1 Introduction Modern roundabouts are circular intersection in which vehicles circulate anticlockwise the circulatory roadway installed around a central island and have
... In Sweden, researchers compared vehicle-to-pedestrian crash data from 72 roundabouts with the expected values from comparable traffic light intersections. They concluded that for single-lane roundabouts, there were three to four times fewer vehicle-to-pedestrian crashes at the roundabouts than at traffic-light-controlled intersections; for two-lane roundabouts, the crash risk was found to be similar to that of comparable intersections [10]. ...
Article
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Vehicle fuel consumption and emission rates in Kuwait have increased considerably over recent decades, and are now causing health and economic problems. A three-lane smart roundabout is a new and innovative design idea that can help to mitigate these issues. The smart roundabout was designed with a dedicated exit lane on the right side of each entryway, and a U-turn path connecting each adjacent entry and exit road. Both features permit vehicles to turn in specific directions without needing to enter the roundabout itself. Underground tunnels were designed for pedestrian and cyclist use. The objective of this study was to measure the impact of a smart roundabout on vehicle fuel consumption and on emissions of carbon dioxide, carbon monoxide, nitrogen oxides, and hydrocarbons. These results were then compared with those of a traditional roundabout and of a light-signalised intersection. Two light-signalised intersections with different traffic volumes were chosen for this study and simulated in their present state, as replaced by traditional roundabouts; and as replaced by smart roundabouts using the SIDRA 6.0 software. The smart roundabout allowed traffic to proceed with minimal delay and idling time, significantly reducing vehicle fuel consumption and emissions in comparison with a traditional roundabout or light-signalised intersection. Furthermore, the smart roundabout allowed pedestrians and cyclists to move safely through the intersection without interacting with vehicular traffic. © 2015, South African Institute of Industrial Engineering. All rights reserved.
... The design and quality of the built environment -road and infrastructure, streetscape -influences the levels of pedestrian crashes as shown by Dai (2012). Several studies (Brude and Larsson, 2000;Retting et al., 2003) have focused the impact of built environment features that increase or decrease crash risk in urban areas. Traffic volumes, parked vehicles, traffic speed and lack of pedestrian facilities were the most frequently mentioned sources of danger by Salter et al. (1993). ...
Article
Traffic crash fatalities from 2006 to 09 in Delhi, India show that pedestrians have the largest share in total road fatalities. Perception of risk provides important information to identify potential crash risk. Thus, the main objective of this paper is to explore the pedestrian perception of risk in getting involved in a traffic crash in different locations and the role of built environment features in risk perception of pedestrians. Locations having a high number of pedestrian fatal crashes were identified using GIS map of Delhi. Pedestrian perceptions of risk at forty-five actual crash sites were collected through questionnaire survey. Risk perception of pedestrians of built environment features were analyzed based on pedestrian demographic characteristics. Ordered logit model was used to examine the influence of these variables on risk perception of respondent’s neighborhood and of the location where the survey was conducted. Seventy percent respondents perceive the neighborhoods where they reside having higher risk than the actual crash locations. Several factors such as gender, number of lanes, sidewalk width, sidewalk maintenance, traffic speed and traffic volume were significantly associated with perceived risk. Survey sites were further categorized into four groups i.e. foot of flyover, four-way junctions below flyover, midblocks and intersections to find the impact of characteristics of locations on pedestrians’ risk perception of different locations. Four-way junctions below flyover were found to have higher perceived risk compared to other locations.
... Despite the data set is limited to a sample of 35 four-leg roundabouts operating in the road network of Palermo City, Italy, and it cannot be considered representative of the national situation (due to atypical features detected in the geometric layouts and driver behavior [13]), a comparison of the above models with other flow-only models for roundabouts known to the authors has been attempted. Figure 4 shows details of these models from the US [19], Sweden [20] and Canada [21]. This figure shows that the model developed in this case study predicts more crashes than the Swedish and US models, especially when the trend is neglected; it predicts less crashes than the Canadian model which is, however, based on more recent data. ...
... The risk of collisions depends on the number of potential conflict points and how well road users are able to handle conflicts. For instance, a roundabout reduces the number of potential conflict points compared to an intersection which has favourable safety effects in general (Elvik 2004), although the effects found for cyclists are not consistent (Brüde and Larsson 2000, Dijkstra 2004, Daniels et al. 2009, Sakshaug et al. 2010 Measures such advance stop lines and bike boxes may make cyclists more visible to motorists (especially right-turning lorries) at signalized intersections in order to reduce crash risk (Hunter 2000, Niewöhner andBerg 2005). The risk of single-bicycle crashes is influenced by how well cyclists are supported when balancing and steering their bicycles, and avoiding obstacles . ...
Thesis
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This thesis is focused on the question how the road environment (road design and network characteristics) affects road safety for cyclists through effects on risk and exposure to risk. This question is relevant because government agencies in many countries aim to improve road infrastructure safety for cyclists to decrease the substantial health burden due to cyclist injuries. This concerns both collisions with motor vehicles which regularly result in fatal injuries as well as single-bicycle crashes (falls or obstacle collisions) in which many cyclists incur serious injuries. The research questions formulated in this thesis address three main topics. The first subject is about how the road environment affects travel behaviour and exposure. The second is about its effect on crash risk (injury risk is only marginally addressed). The third topic is the relationship between exposure and risk, because both may affect one another. One of the innovative aspects of this thesis is that it contains studies related to all three topics (exposure, risk and their relationship), aiming to increase the knowledge of how the road environment contributes to or helps to prevent bicycle crashes. Most research is restricted to one of the three issues. Chapter 1 describes a conceptual framework which combines exposure to risk, risk, and the relationship between them. The framework’s three determinants for travel behaviour are locations of activities; resistances (generalized transport costs); needs, opportunities, and abilities. Crash and injury consequences are modelled by the three ‘safety pillars’: infrastructure, road users and the vehicles they use. The framework’s link between risk and exposure is important because of the ‘non-linear relationship’ between these two, i.e. risk tends to decrease as exposure increases. Finally, the framework has a link from (perceived) risk to resistance because perceived risk plays a role in travel behaviour, e.g. a road user may prefer driving over cycling because cars are perceived to be safer. The remainder of this summary is organized according to the three research topics. The road environment may encourage or discourage cycling which affects exposure to risk. It depends on the relationship between exposure and risk to what extent the number of road traffic casualties is affected. Chapters 2 and 3 focus on the following research question: How does a modal shift from short car trips to cycling affect road safety? To answer this question, Crash Prediction Models (CPMs) were developed forDutch municipalities. Models were also developed for single-bicycle crashes which was not done before. As single-bicycle crashes are under-reported by the police, the study also included another data source: self-reported crashes from a questionnaire study. It was found that cyclists are less likely to be involved in a severe single-bicycle crash in municipalities with a high amount of cycling. The volumes of cyclists and motor vehicles before and after a hypothetical modal shift were entered into the CPMs to estimate the road safety effects. The results suggest that, under conditions such as in Dutch municipalities, transferring short trips made by cars to bicycles does not change the number of fatalities, but increases the number of serious road injuries. The rise in the number of serious road injuries is due to high numbers of severe single-bicycle crashes. The effect of a modal shift is dependent on the age of the population in which the shift is concentrated, i.e. more favourable for young and less favourable for older drivers. Furthermore, the results suggest that it may be possible to influence the effect of a modal shift by measures specifically affecting cyclists’ risk. Chapter 4, 5, and 6 are focused on road design and crash risk. Chapters 4 describes a study conducted to answer question 3a: How is the design of unsignalized priority intersections related to bicycle–motor vehicle crashes? In this study, the safety of cyclists at unsignalized priority intersections within built-up areas is investigated. Failure-to-yield crashes recorded at unsignalized intersections were classified into two types based on the movements of the involved motorists and cyclists: • type I: through bicycle related collisions where the cyclist has right of way (i.e. bicycle on the priority road); • type II: through motor vehicle related collisions where the motorist has right of way (i.e. motorist on the priority road). The probability of each crash type was related to its relative flows and to independent variables using negative binomial regression. The results show that more type I crashes occur at intersections with two-way bicycle tracks, well-marked, and reddish coloured bicycle crossings. Type I crashes are negatively related to the presence of raised bicycle crossings (e.g. on a speed hump) and other speed reducing measures. The accident probability is also decreased at intersections where the cycle track approaches are deflected between 2 and 5m away from the main carriageway. No significant relationships are found between type II crashes and design factors such as the presence of a raised median. Chapter 5 focuses on research question 3b: What single-bicycle crash types can be distinguished and can these be related to infrastructure?A literature search showed that only a few studies addressed single-bicycle crashes (i.e. a fall or obstacle collision). These studies and theories were used to develop a draft categorization of single-bicycle crash types. The typology was tested using a survey among bicycle crash victims treated at Emergency Care Departments. The results indicate that about half of all single-bicycle crashes are related to infrastructure: the cyclist collided with an obstacle (1ai), rode off the road (1aii), the bicycle skidded due to a slippery road surface (1bi), or the rider was unable to stabilize the bicycle or stay on the bike because of an uneven road surface (1bii). The first two categories happen due to the cyclist inadvertently taking a dangerous riding line, while the last two happen under more direct influence of the road surface conditions. Crash types related to the cyclist are loss of control at low speed (2a), due to forces on the front wheel (2b), or poor or risky riding behaviour (2c). Bicycle defects (3) contribute to a small group of crashes. Finally, some cyclists fall because of an external force such as a gust of wind (4). Question 3c is about the role of visibility of infrastructure in single-bicycle crashes: What do cyclists need to see to avoid single-bicycle crashes?This question is addressed in Chapter 6. To study the role of visual characteristics of the infrastructure, such as pavement markings, in single-bicycle crashes, a study in two steps was conducted. In Study 1, a questionnaire study was conducted among bicycle crash victims. Logistic regression was used to study the relationship between the crashes and age, light condition, alcohol use, gaze direction and familiarity with the crash scene. In Study 2, the image degrading and edge detection method (IDED-method) was used to investigate the visual characteristics of 21 of the crash scenes. The results of the studies indicate that crashes, in which the cyclist collided with a bollard or road narrowing or rode off the road, were related to the visual characteristics of bicycle facilities. Chapter 7 focuses on network characteristics and cycling safety. It addresses the first research question: How does network-level separation of vehicular and cycle traffic (unbundling) in urban networks affect road safety? This is related to the distribution of traffic over space, one of the elements of travel behaviour. Bicycle-motor vehicle crashes are concentrated along distributor roads where cyclists are exposed to greater volumes of high-speed motorists than they would experience on access roads. This study examined the road safety impact of unbundling vehicular and cycle traffic in Dutch urban networks. Unbundling is operationalized as the degree to which cyclists use access roads and grade-separated intersections to cross distributor roads. The effect on the share of cycling in the modal split is also assessed as unbundling measures may affect the competitiveness of cycling compared to driving. The analyses were conducted using data of all Dutch municipalities with more than 50,000 inhabitants. Negative binomial regression was used to analyse the effect on the number of police-reported cyclist deaths and in-patients in bicycle-motor vehicle crashes. A mediation model was tested, with Structural Equation Modelling hypothesizing that unbundling corresponds positively with the cycling modal share via the length of car trips divided by those by bicycle. The results of this study suggest that unbundling improves cycling safety, and increases the share of cycling in the modal split (as a result of improved competitiveness of cycling in terms of trip length). Chapter 8 discussed the main findings of the research conducted throughout the thesis and considered the implications. It can be concluded that cycling safety is affected by the road design. For instance, the studies described in Chapters 4, 5, and 6 indicate that the design of bicycle tracks and intersections affect the likelihood of BMV and single-bicycle crashes. Chapter 7 indicates that network characteristicsare related to the likelihood of BMV crashes due its effect on the distribution of vehicular and cycle traffic over the network. This affects cyclists’ exposure to high-speed vehicular traffic. The road environment may encourage or discourage cycling. For example, the study described in Chapter 7 suggest that the measures taken for unbundling correspond positively with the modal share of cycling because trips become relatively shorter by bicycle then by car. In Chapters 2 and 3 it is estimated that under conditions such as in Dutch municipalities, transferring short trips made by cars to bicycles does not change the number of fatalities, but increases the number of serious road injuries. Chapter 8 discusses a number of uncertainties regarding the latter conclusion. A more favourable road safety impact can be expected if the modal shift would be induced by instance network-level separation or other safety-related measures than if it were induced by factors unrelated to safety (e.g. an increased gasoline price). The chapterdiscusseschallengesforfuture research.
... However, there are some two lane approaches where the number of accidents is lower, according to the distribution of the indicator (34%). In the before-after studies by Daniels et al. (34) and Persaud et al. (11), roundabout approaches with two lanes tended to perform worse, and Brüde & Larsson (18) stated that the number of lanes is a significant variable. ...
Article
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Abstract Roundabouts have been widely used in the UK on all road classes, as they are generally considered safer than other types of intersections. The objective of this study is to examine geometric and traffic characteristics and their influence on accident numbers. The study comprises 70 roundabouts (284 approaches). The data used included all recorded vehicle accidents, geometric, and traffic characteristics for whole roundabouts, within the circulatory lanes, and at approaches to the roundabouts. Random-parameters negative binomial count data models were used to estimate model parameters and the models were compared with fixed-parameters negative binomial count data models. The random-parameters models provide better goodness of fit and more variables were found to be significant, relative to the fixed-parameters model. Total approach traffic, truck percentage, entry width, inscribed circle diameter, number of lanes, and presence of traffic signals were found as significant variables influencing accident occurrences. Keywords: Roundabout, accidents, random-parameters, fixed-parameters
... It is common to use STOP signs at intersection legs in order to manage traffic, thereby enhancing security. [2]. According to the National Highway Traffic Safety Administration, onethird of intersection-related crashes, as well as over 40% of fatal collisions, occurred at intersections controlled by STOP signs; this explains the increased use of roundabouts. ...
Article
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We propose a system for monitoring the driving maneuver at road intersections using rule-based reasoning and deep learning-based computer vision techniques. Along with detecting and classifying turning movements online, the system also detects violations such as ignoring STOP signs and failing to yield the right-of-way to other drivers. There is no distinction between temporarily and permanently stopped vehicles in the majority of frameworks proposed in the literature. Therefore, to conduct an accurate right-of-way study, permanently stopped vehicles should be excluded not to confound the results. Moreover, we also propose in this work a low-cost Convolutional Neural Network (CNN)-based object detection framework able to detect moving and temporally stopped vehicles. The detection framework combines the reasoning system with background subtraction and a CNN-based object detector. The obtained results are promising. Compared to the conventional CNN-based methods, the detection framework reduces the execution time of the object detection module by about 30% (i.e., 54.1 instead of 75ms/image) while preserving the same detection reliability. The accuracy of trajectory recognition is 95.32%, that of the zero-speed detection is 96.67%, and the right-of-way detection was perfect
... The increased safety of roundabouts occurs as a result of reducing the number of conflict points compared to conventional intersections, slower speed when entering, and throughout intersections, which also makes roundabouts safer for pedestrians [15][16][17][18]. Reducing the number of conflict points is related primarily to the conflicts between vehicles [19] [20]. ...
Article
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Intersections present a big safety problem in traffic since there has been an increased risk of crashes because of conflicts in the flows intersecting. A great number of studies done in the world show that roundabouts are safer than conventional intersections since it has been recorded that after the conversion to roundabouts the number of crashes has been decreasing. The research on applying Empirical Bayes (EB) method has been conducted by using 15 two-lane intersections in the city of Niš (Serbia), which have been converted into large compact two-lane roundabouts during the period of 2005-2013. The results show that the conversion of conventional intersections into roundabouts has positive effect on reducing the number of crashes. For all intersections, the reduction of crashes is estimated at around 76% for all crashes, i.e. 80% for the crashes with injuries. For different groups of intersections the effects are determined separately. © 2016, Faculty of Transport and Traffic Engineering. All rights reserved.
... In the US, using data from before-and-after the installation of 24 modern roundabouts, there was a 76% reduction in injuries and an 89% reduction in fatalities (Retting et al. 2001). A Swedish study found that the observed number of pedestrian crashes on single-lane roundabouts was 3-4 times lower than what was predicted, which suggests that single-lane roundabouts should be preferred over other designs in pedestrian-heavy areas (Brude and Larsson 2000). ...
Article
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Vision Zero (VZ) is a public program that aims to have zero fatalities or serious injuries from road traffic crashes. This article examines various major components of VZ: how VZ redefines road safety, how VZ principles and philosophies can be applied to modern car and road designs, and how VZ can be applied to traffic. Applications of these principles to real-world traffic infrastructure are explored in order to show policymakers the toolkits available to increase road safety while taking into consideration local contexts.
... Promoting the safety education of pedestrians has been primarily considered in developed countries though they are not confident about the effects of these trainings and need more time (Duperrex et al., 2002;Wiener, 1968). Engineering measures in the built environment are more concerned and are generally categorized into three types (Retting et al., 2003): (1) separating pedestrians from vehicles through methods like signal phasing or markings on pavements (Ewing and Dumbaugh, 2009;Guo et al., 2020;Retting et al., 1996;Van Houten et al., 2000;Zheng et al., 2021), (2) increasing the visibility of pedestrians with LED lights, 3D crosswalks (Koepsell et al., 2002;Patella et al., 2020;Pichayapan et al., 2020;Uttley and Fotios, 2017), and (3) managing the vehicle speeds (Brude, 2000;Elvik, 2003;Kraus et al., 1996). ...
Article
Due to the high volume of documents in the pedestrian safety field, the current study conducts a systematic bibliometric analysis on the researches published before October 3, 2021, based on the science-mapping approach. Science mapping enables us to present a broad picture and comprehensive review of a significant number of documents using co-citation, bibliographic coupling, collaboration, and co-word analysis. To this end, a dataset of 6311 pedestrian safety papers was collected from the Web of Science Core Collection database. First, a descriptive analysis was carried out, covering whole yearly publications, most-cited papers, and most-productive authors, as well as sources, affiliations, and countries. In the next steps, science mapping was implemented to clarify the social, intellectual, and conceptual structures of pedestrian-safety research using the VOSviewer and Bibliometrix R-package tools. Remarkably, based on intellectual structure, pedestrian safety demonstrated an association with seven research areas: “Pedestrian crash frequency models”, “Pedestrian injury severity crash models”, “Traffic engineering measures in pedestrians’ safety”, “Global reports around pedestrian accident epidemiology”, “Effect of age and gender on pedestrians’ behavior”, “Distraction of pedestrians”, and “Pedestrian crowd dynamics and evacuation”. Moreover, according to conceptual structure, five major research fronts were found to be relevant, namely “Collision avoidance and intelligent transportation systems (ITS)”, “Epidemiological studies of pedestrian injury and prevention”, “Pedestrian road crossing and behavioral factors”, “Pedestrian flow simulation”, and “Walkable environment and pedestrian safety”. Finally, “autonomous vehicle”, “pedestrian detection”, and “collision avoidance” themes were identified as having the greatest centrality and development degrees in recent years.
... Ainsi, les auteurs démontrent que la présence de bandes cyclables dans le giratoire est associée à une augmentation moyenne significative de 93 % des collisions avec traumatismes (photo 9). Une autre étude mentionne que les risques de collisions et de traumatismes sont plus élevés dans les giratoires dont le diamètre de l'îlot central est de moins de 10 mètres (Brude et Larsson, 2000). Au Danemark, une étude de Jensen (2013) a aussi évalué la performance de la conversion d'intersections vers des carrefours giratoires. ...
... Crash statistics suggest roundabouts' safety advantage for vehicle occupants (Elvik, 2003;Retting, Persaud, Garder, & Lord, 2001;Rodegerdts et al., 2010). For pedestrians, the scant literature suggests that multilane roundabouts may be as safe for sighted pedestrians as traditional intersections, whereas single-lane roundabouts may be safer (Brude & Larsson, 2000;Lalani, 1975;Schoon & van Minnen, 1993, 1994. ...
Article
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The aim of this study was to evaluate the relative risk and efficiency of road crossing experienced by blind and sighted pedestrians at a single-lane roundabout with two levels of traffic volume and at two distances from the roundabout. With the rapid spread of modern roundabouts across the United States,their accessibility to blind pedestrians has become an important concern. To date, accessibility research relevant to blind pedestrians has focused on multilane roundabouts, and single-lane roundabouts have been virtually ignored. Blind and sighted participants made judgments about when they would cross a single-lane roundabout with high and low traffic volumes, at exit and entry lanes, and at the actual crosswalks and at locations farther from the roundabout. Relative to sighted participants, blind participants' judgments about when to cross were more frequently risky, especially when traffic volume was high. Blind participants also were slower to make crossing judgments and accepted fewer crossing opportunities. Both groups made somewhat safer and more efficient judgments at locations farther from the roundabout. Some single-lane roundabouts may pose greater risk to blind pedestrians than to sighted pedestrians, especially when traffic volume is high. Crosswalk location merits further investigation as a design issue. These findings are relevant to transportation planners and engineers who are responsible for the accessibility of public rights-of-way.
... Prior to construction of the roundabouts, there were 10 injury crashes per year, and in the four years after the roundabouts were built, only 1 injury crash was reported (Hartman as cited in Isebrands et al., 2008). Studies of pedestrian safety in Europe have shown that installation of single-lane roundabouts reduce pedestrian crashes by about 75% to 80% compared to signalization (Brude and Larsson, 2000;Schoon and van Minnen, 1994). There are many health benefits connected to active transportation. ...
Article
This article discusses the risk of traveling with different modes and how different policy and infrastructure design choices could improve the safety of people traveling. It is concluded that if we look at fatality risk, accidents, or unintentional crashes far outnumber intentional injury from terrorism and other crime, at least in most countries. Suicides are not dealt with in this article, but that number is also substantial. A similar number of people as die in accidents, die as a result of breathing polluted air or being exposed to transportation-related toxins in other ways. Large number of people also die from health issues originating with transportation-related noise. Finally, pandemics, like Covid-19, can spread from continent to continent by airplanes and cruise ships and then locally by other modes of transport. Certainly, nonfatal injuries from crashes as well as from crime, ranging from verbal abuse to rape and serious assault, are also of grave concern. If looking at different modes, it is concluded that travel by air and rail is much safer than travel by automobile. Being an unprotected road user has the highest risks. The risks for all roadway modes can be significantly reduced by redesign of infrastructure, in particular by introducing designs reducing speed and reducing the number of conflict points.
... By appropriately developing the geometry of roundabout entries, it is possible to force road users to reduce driving speed to an extent that depends on the entry's geometrical parameters. With well-designed roundabout geometry, such driving speed reduction can reach up to several dozen per cent, thus contributing to a significant decrease in the number of accidents and reduction of their consequential severity [9][10][11][12]. ...
Chapter
The main purpose of roundabouts is road traffic calming by triggering a vehicle motion trajectory change before entering the roundabout and consequential traffic deceleration when crossing the roundabout area. The article provides a discussion on results of research concerning vehicle motion trajectory at one-lane roundabouts. Specific cases have been studied to analyse the effect of one-lane roundabout geometry on vehicle motion trajectory. The relevant survey was conducted by video recording a road traffic scene at a roundabout. An image thus obtained made it possible to determine what is referred to as a dipped headlight track of vehicles by application of the Harris algorithm. The vehicle motion trajectories recorded in the survey were subject to statistical analysis in order to reveal any potential regularities that could be relevant to assessment of the current roundabout geometry. The measuring method proposed is more flexible compared to other vehicle motion trajectory recording techniques, as it enables vehicular traffic to be studied under most weather and illumination conditions, including at night, in non-illuminated road sections, and even in fog.
... Standing to Poudel and Singleton (2021) 49 articles dealt with bicycle safety at roundabouts, of these 32 are crash data studies. Bicyclists' perception of roundabouts was tackled by 8 studies, among which there are Arnold et al (2010), Cambell et al. (2006, Hyden and Várlelyi (2000), Jensen (2013), Møller and Hels (2008), Tan et al. (2019), which investigate their comfort, risk, danger and avoidance of this kind of infrastructure, while design characteristics have been investigated by five research works, among them Brüde and Larsson (2000), Daniels et al. (2010), Orozova-Bekkevold (2007), Turner et al. (2009). Pedestrian safety at roundabouts has also been identified as an important issue. ...
Article
Background: Roundabouts are considered one of the safest infrastructure typologies, when referring to motorized traffic. Due to their ability to reduce conflict points between vehicles, they have been largely spread, substituting signalized or unsignalized intersections. While the increase in safety for drivers has been largely tackled and demonstrated by researchers, and some efforts have been spent on the side of cyclists, pedestrian safety has not been extensively analyzed yet. Aim: The present paper aims at analyzing pedestrian safety at roundabouts set in two different locations, Italy and Slovenia. This research will highlight differences and similarities in the behavior of walkers at the same type of infrastructure, taking into account the effects risen by diverse road habits typical of the two countries. Methodology: Starting from video footages recorded at the two locations, behavioral analysis, pointing out pedestrian speed, acceleration and crossing time, and a proactive safety analysis, calculating surrogate safety measures for vulnerable road users, have been run. Descriptive statistics and additional statistical tests are developed to compare the two data samples. Conclusions: From the behavioral point of view, results show for both locations faster pedestrian paces than expected, with the Slovenian case having the highest speed values and lowest crossing times. As regarding the safety point of view, Time-to-Collision, Time Advantage and relative speed between oncoming vehicles and the crossing pedestrians permitted to objectively evaluate conflict severity. The calculated percentages of values overcoming the individuated thresholds for determining dangerous events underlines the need to find solutions from both the infrastructural side and pedestrian awareness about their safe behavior.
... Owing to the omission of left turns, roundabouts had a greater traffic capacity [26]. A central channelized island could be safer if its diameter was greater than 10 m [27]. To further prevent traffic from weaving, Wang et al. [28] presented a novel method for improving the center island design based on the spiral-shaped driveways. ...
Article
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At intersections, road features related to different maneuvers such as left-turn, right-turn, and central channelization (i.e., guide lines and channelized islands), are widely used to decrease the traffic conflicts and improve the safety and mobility of traffic. However, there are several main problems related to channelization design at intersections including poor recognizability, unreasonable entering speed, insufficient sight distance, and relatively low merging speed. To address these problems, this paper focused on developing a method to assess how to design intersection features by dividing the driving process through intersections into four stages: “appearance of channelization” - “beginning of channelization” - “middle of channelization” - “end of channelization”. Drivers’ visual lane models were established based on the Catmull-Rom spline to quantify visual road information perceived by drivers. Shape parameters and three characteristic regions were extracted from these models. Naturalistic driving experiments and 3D mobile mapping experiments were conducted at intersections with channelized islands or guide lines. Driving speed distributions in the four stages were found to obey normal distributions and could be calculated by shape parameters with Bayesian inference. Then, 3D mobile mapping was used as a substitute for extensive naturalistic driving experiments to obtain drivers’ visual perception from all possible visual angles. An evaluation method on intersection design was built and used to identify which stage of channelization needs to be modified. This new method helps to enhance the safety and efficiency of intersections.
... • bridges or underpass the roundabout as tunnels. Separated cycle paths at roundabouts are seen as the best solution in Sweden [16]. In terms of geometric design for roundabouts, [17] recommended tangential design for roundabouts in Sweden in order to keep speed and capacity of vehicles. ...
Article
Cycling is a sustainable transport mode, especially in urban areas for short distances. Electric bikes and electric scooters are increasingly emerging into traffic network in cities in Sweden due to advantages related to accessibility, environment, etc. However, they bring questions in terms of traffic risk and accidents. The road infrastructure must be adapted to accommodate the increasing share of these new types of bikes in traffic. The study will assess both bikes and e-bikes safety according to exposure, risk and consequences. The study will review relevant literature on Traffic Calming Measures (TCMs). It will develop a conceptual framework to determine the impact of different TCMs (horizontal and vertical) on traffic safety for both traditional and e-bikes safety. Accident data from the Swedish Traffic Accident Data Acquisition (STRADA) will be collected and analysed in order to identify roundabouts (as a chosen type of TCMs) with high accidents rates for cyclists in Norrkoping city in Sweden.
... Review. Several international studies employed speed variables in their SPFs (e.g., 23,44,56,57). On the other hand, some of the studies did not succeed, for example NCHRP Project 3-65 (30), in which the estimated model was deemed inadequate on the basis of weak effects of speed variables. ...
Article
Roundabouts are considered the safest intersection design; however, the safety effect may not be satisfactory at each specific roundabout. This is true especially in countries where roundabout design is a relatively new concept, such as in the Czech Republic. Specifically, most Czech roundabout crashes were found to occur on entries. This motivated the presented study to investigate how entry design parameters influence safety on Czech roundabouts and, if possible, use the findings to update current Czech roundabout design guidelines. To this end, the study comprised three analyses: crash-based safety performance functions, speed analysis, and finally safety performance functions which incorporated speed. All three analyses proved that entry design parameters have a statistically significant influence on safety, in terms of crash frequency, severity and speeds. Given the study objective, this fact should be considered in Czech roundabout design guidelines.
... While the results of international research on cycling safety at roundabouts is inconsistent (see e.g. Brüde and Larsson, 2000, Daniels et al., 2009, Sakshaug et al., 2010, the results of Dutch studies suggest converting intersections to roundabouts reduces crashes with cyclists and mopeds by some 60% (Van Minnen, 1990). Roundabouts with higher volumes of motor vehicles (over 4,000 passing motor vehicles per day) are substantially safer with cycle tracks compared to cycle lanes, i.e. a threefold lower crash rate (Van Minnen, 1995). ...
Article
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Bicycle infrastructure is utilised to improve cycling safety and encourage bicycle use as a sustainable and healthy transport mode. This study sets out to assess whether providing physically separated cycle tracks along distributor roads, as prescribed in Dutch design guidelines and the Sustainable Safety vision, yields the expected safety benefits for cyclists. Therefore the safety of physically separated cycle tracks is compared to marked or painted cycle lanes and to mixed traffic conditions at distributor roads with a speed limit of 50 km/h in Amsterdam in the Netherlands. The study also includes the presence of the risk factors curbside parking and trams. Since police records are known to underreport single bicycle crashes and other crashes without a motor vehicle involved, ambulance records are used in this study instead. Also, both motor vehicle volumes as well as cyclists counts are taken into account in the crash analysis. By doing so, this study aims to address two weaknesses of previous research, i.e. the lack of control for exposure of cyclists and the use of police recorded crashes which miss the majority of bicycle crashes without motor vehicles. Results show that, controlled for kilometres travelled by bicycle and by motor vehicle, 50-60% less bicycle crashes occur on distributor roads with cycle tracks compared to those with cycle lanes. Curbside parking and trams are related to an increased likelihood of bicycle crashes, a difference of a factor 2 and 1.7-2 respectively. The authors therefore recommend to favour physically separated cycle tracks over cycle lanes and to take out curbside parking from the cross section as this presents the possibility to introduce cycle tracks in existing cross sections and mitigate an important risk factor concurrently.
Article
The increasing number of roundabout intersections is due in part to the fact that they significantly reduce death and injury rates for motor vehicle occupants. However, roundabouts can exacerbate the challenges that pedestrians with visual impairments encounter when crossing streets. Pedestrians who are blind must use their hearing to perceive gaps in traffic that are long enough to permit crossing the street, or they must detect when vehicles have yielded for them. Strategies to enhance the ability of individuals who are blind to detect gaps and to detect vehicles that have yielded for them are needed to increase access to these intersections by individuals who are blind.
Book
The world trend in automotive industry represents the improvement of the existing vehicle power plants and their further development as well as the use of various alternative fuels. Such tendencies should not be considered only from an entirely technical aspect, but also from the economic, social and strategic aspects of the modern society. In this sense it is necessary to give priority to biodiesel fuel. The production of biodiesel fuel has to be developed in compliance with the increasingly severe exhaust emission standards in designing and realization of road transport means. From the economic aspect at macro-economic level, the development of biodiesel will reflect on the condition of industrial production, employment, additional inflow of financial means into agriculture and the economic development of rural areas, as well as the foreign currency reserves of a country along with the reduction in the dependence of macroeconomic parameters on the external factors.
Conference Paper
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Much is known about pedestrian behaviour and crash risk in developed countries. In contrast, the literature on pedestrian crash risk in developing countries reveals wide gaps in knowledge and understanding, and a comprehensive assessment is lacking. In particular, pedestrian behaviour in developing countries is fundamentally different in comparison to developed countries, and is influenced by a variety of less well understood contributing factors, leading to difficulty in modelling and predicting pedestrian crash risk and in turn identifying effective safety countermeasures. This paper provides a comprehensive synthesis of the factors known to influence pedestrian crash risk in developing countries, then focuses on Ethiopia as a specific example. The paper identifies where critical gaps in knowledge exist regarding pedestrian crash risk and associated behaviour in developing countries--a set of knowledge gaps which collectively are significant. The paper concludes by articulating a critical research path moving forward, with the aim to achieve an improved understanding of developing country pedestrian crash risk, and an ultimate goal of identifying effective pedestrian safety countermeasures suited to the unique challenges faced by transport system managers in developing countries.
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Urban bicycling has been largely marginalized for decades in the global north and south. Despite a renaissance over the last two decades in academic research, political discourse, sustainability activism, and planning, cities often struggle with data quality and quantity. Digitalization has led to more and better data sources, but they still must be validated and compared with findings from conventional travel surveys. With the COVID-19 pandemic, bicycling and associated road facilities expanded, as did road crashes involving bicycles. This study utilized tens of thousands of datapoints sourced by public institutions and digital devices belonging to private companies that have spread across Berlin over the last ten years and are currently ubiquitous. What does an integrated analysis of data from these novel sources reveal for urban bicycling research, planning, and network design? We explored and visualized the relationships and spatiotemporal variations in (i) bicycling volumes and (ii) crashes, unveiling the (iii) distribution of and correlation between datasets and the city's bikeway network at an unprecedented threshold. The findings can be useful for special interest groups and to guide future urban bicycling research, planning, and network design.
Article
Objectives: Roundabouts are a type of circular intersection control generally associated with a favorable influence on traffic safety. International studies of intersections converted to roundabouts indicate a strong reduction in injury crashes, particularly for crashes with fatal or serious injuries. Nevertheless, some crashes still occur at roundabouts. The present study aims to improve the understanding of roundabout safety by identifying crash types, locations, and factors that are associated with roundabout crashes. Methods: An analysis of 399 crashes on 28 roundabouts in Flanders, Belgium, was carried out based on detailed crash descriptions; that is, crash data and collision diagrams. The crashes are sampled from police-reported crashes at roundabouts in the region of Flanders, Belgium. Collision diagrams of the registered crashes were used to distinguish 8 different crash types. The roundabout itself is divided into 11 detailed and different typical segments, according to previously established knowledge on the occurrence of crashes at roundabouts. The 8 roundabout crash types are examined by injury severity, crash location within the roundabout, type of roundabout, type of cycle facility, and type of involved road user. Results: Four dominant crash types are identified: rear-end crashes, collisions with vulnerable road users, entering-circulating crashes, and single-vehicle collisions with the central island. Crashes with vulnerable road users and collisions with the central island are characterized by significantly higher proportions of injury crashes. About 80% of the crashes occurred on the entry lanes and the circulatory road (segments 1-4). Road users who are the most at risk to be involved in serious injury crashes at roundabouts are cyclists and moped riders. Conclusions: The main goal of this study was to identify and analyze dominant crash types at roundabouts by taking into account detailed information on the crash location. Some connections between certain roundabout crash types, their crash location, and roundabout design characteristics have been found.
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ABS"rRACT: Roundabouts, under the right circumstances, are quickly proving themselves to the North American transportation engineer as a viable intersection treatment for both urban and rural roadways. The design of roundabouts is a complex procedure involving several variables, which need to be addressed to ensure a design is safe and has adequate capacity. A principle based design approach that balances the competing objectives of safety, capacity, and cost allows the designer to achieve a good solution for a particular site. Ideally, these design principles provide the engineer the flexibility to tailor a design to meet differing needs. For example, a slower entry andlor exit speed for increased pedestrian safety, or surfacing treatments for the visually impaired, or geometric configurations promoting higher capacity. Because good design is not a one-size fits all approach, following a 'prescriptive' standard design methodology applied across the entire range of roundabouts will not result in balanced designs. Creating added confusion for designers is the fact that Europe, Australia, and the UK each have different sets of design principles, in some cases contradictory, which have evolved based on varying levels of research. Roundabouts have their own set of advantages and disadvantages when comparing pedestrian and cyclist treatments to those provided at conventional intersections. The literature shows, given a properly designed roundabout facility, that vehicular and pedestrian safety at roundabouts, is almost always improved when compared to conventional intersections. Results regarding cyclist safety are somewhat mixed. Due to the elimination of conflict points at roundabouts and the lower speed differentials compared to conventional intersections, accident severity for all users is often significantly reduced when collisions occur, although frequency may increase.
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Pedestrian fatalities constitute about 30% of the deaths caused by road traffic crashes in India. The proportion of pedestrian fatalities in large cities (Delhi, Mumbai, etc.) varies from 50% to 60% and is about 20% to 30% on national and state highways. Pedestrians are present on all road categories in urban as well as rural areas. At least 20% to 40% of work trips are taken as pedestrian trips in most Indian cities. However, on pedestrian facilities such as footpaths, safe crossing facilities are not present in most Indian cities. Even when present, their poor maintenance and poor construction quality make them unusable. As a result, pedestrians are forced to share the road space with motorized vehicles and to cross the roads where there is no safe pedestrian crossing. This paper attempts to study pedestrian behavior-walking along the road and crossing the road-by detecting pedestrians with the use of a vehicle-mounted camera. The vehicle is driven on various categories of roads at different times. The data collected with this method are varied temporally as well as spatially. A smartphone-based GPS logging app was used to collect telemetry data, which were synced with the camera feed. The objective of this study was to understand pedestrian behavior-walking on the road versus a footpath in the presence of various road features, such as the number of lanes, presence of medians, and presence of footpaths. The influence of the presence of public transport stops, junctions, foot bridges, and grade-separated junctions (flyover) on pedestrian crossing behavior was studied.
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In generale si definisce “utente debole ” il soggetto che, in caso di collisione tra due o più utenti della strada, risulta il più vulnerabile. Tra questi, le utenze che non sono fisicamente protette (pedoni, ciclisti e conducenti di ciclomotori) si possono considerare le più vulnerabili.In tal senso è possibile inoltre distinguere diversi livelli di vulnerabilità (si considerano come maggiormente vulnerabili i pedoni, seguiti dai ciclisti e dai conducenti di ciclomotori) e diverse abilità o, come nel caso dei pedoni, diversi livelli di capacità motoria. Pertanto i pedoni anziani o bambini sono considerati utenti più deboli rispetto al pedone normodotato, così come i pedoni portatori di handicap o con difficoltà motorie; gli anziani ciclisti o conducenti di ciclomotori rappresentano un‟ulteriore categoria di utenza particolarmente a rischio. Il presente lavoro vuole riportare in parallelo gli sviluppi che la ricerca del settore sta portando avanti relativamente la definizione geometrica delle nuove delle intersezioni a raso e la ricerca correlata agli utenti deboli ,considerando inoltre il crescente aumento della popolazione over 65 in tutta
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This paper explores the relationship between sight distance parameters, crash rates, and operating speeds at low-volume single-lane roundabouts in the United States. The understanding of the interaction of design, operations, and crash performance is a step forward in the development and application of performance-based standards for roundabouts. The specific objective of this paper is to quantify the relationship between crash rates, sight distance parameters, and operating speeds to present an approach to establishing performance-based standards that highway practitioners can adopt in roundabout design. Geometric, traffic, and crash data were collected on 72 approaches to 19 low-volume single-lane roundabouts in six states. The data for these sites were broken into two groups based on the posted speed limit (at 40 km/h and greater than 40 km/h). In addition, the associations between different sight distance parameters, crash parameters, and operating speed data were investigated. The research findings provided insight into relating the operational and safety effects of sight distance geometry at roundabouts. This research also identified a methodology that provides guidance as to the development of performance-based standards that rely on a better understanding of these relationships. In general, the research findings were consistent with previously conducted studies and indicated that exceeding sight distance thresholds increases the risk of crashes occurring. It was also found that exceeding sight distance thresholds yielded greater speed differentials between the approach and the entry to these roundabouts. The results of this research can advance the state of practice in understanding the relationships of sight distance design attributes, operational characteristics, and safety metrics for low-volume single-lane roundabouts, which is necessary to the creation of performance-based standards. (C) 2013 American Society of Civil Engineers.
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Pedestrian crashes represent about 40% of total fatal crashes in low-income developing countries. Although many pedestrian crashes in these countries occur at unsignalized intersections such as roundabouts, studies focussing on this issue are limited. The objective of this study is to develop safety performance functions for pedestrian crashes at modern roundabouts to identify significant roadway geometric, traffic and land use characteristics related to pedestrian safety. To achieve this, detailed data including various forms of exposure, geometric and traffic characteristics, and spatial factors such as proximity to schools and proximity to drinking establishments were collected from a sample of 22 modern roundabouts in Addis Ababa, Ethiopia, representing about 56% of such roundabouts in Addis Ababa. To account for spatial correlation resulting from multiple observations at a roundabout, both the random effect Poisson (REP) and random effect Negative Binomial (RENB) regression models were estimated. Model goodness of fit statistics reveal a marginally superior fit of the REP model compared to the RENB model. Pedestrian crossing volume and the product of traffic volumes along major and minor road had significant and positive associations with pedestrian crashes at roundabouts. The presence of a public transport (bus/taxi) terminal beside a roundabout is associated with increased pedestrian crashes. While the maximum gradient of an approach road is negatively associated with pedestrian safety, the provision of a raised median along an approach appears to increase pedestrian safety at roundabouts. Remedial measures are identified for combating pedestrian safety problems at roundabouts in the context of a developing country.
Article
As roundabouts become increasingly popular, and as many communities promote bicycle use, the safety of roundabouts for people bicycling is of major concern. Although converting an intersection to a roundabout may reduce crashes overall, some research from northern Europe suggests that roundabouts may actually increase the frequency of bicycle crashes. We perform a systematic literature review on this topic, reviewing 49 different resources with empirical findings (most from Europe, some from Australia/New Zealand, few from the US). Many studies analyse (limited) bicycle crash data or observe driver/cyclist behaviours and interactions, while a few survey cyclists’ safety perceptions. Consistent with design guidance, bicycle safety performance is worse for higher-speed, multilane roundabouts and when on-roadway bike lanes are provided. Crash data and observations suggest that when cyclists “take the lane” and operate as vehicles – as is allowed or even recommended in some current design guidelines – this leads to conflicts and crashes between circulating cyclists and entering drivers who may have “looked but failed to see” (and thus failed to yield to) the cyclist. Providing separated cycle paths around the roundabout seems to be a lower-risk and more comfortable design solution, although care must be taken to encourage appropriate yielding at crossings. Future research should investigate more design features, socio-demographic characteristics, cyclist safety perceptions, and impacts outside of Europe. Studies should continue to explore ways to overcome limited bicycle crash and exposure data and to utilise naturalistic methods, driving simulators, and stated choice experiments.
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Much is known about pedestrian behaviour and crash risk in developed countries. In contrast, the literature on pedestrian crash risk in developing countries reveals wide gaps in knowledge and understanding, and a comprehensive assessment is lacking. In particular, pedestrian behaviour in developing countries is fundamentally different in comparison to developed countries, and is influenced by a variety of less well understood contributing factors, leading to difficulty in modelling and predicting pedestrian crash risk and in turn identifying effective safety countermeasures. This paper provides a comprehensive synthesis of the factors known to influence pedestrian crash risk in developing countries, then focuses on Ethiopia as a specific example. The paper identifies where critical gaps in knowledge exist regarding pedestrian crash risk and associated behaviour in developing countries-a set of knowledge gaps which collectively are significant. The paper concludes by articulating a critical research path moving forward, with the aim to achieve an improved understanding of developing country pedestrian crash risk, and an ultimate goal of identifying effective pedestrian safety countermeasures suited to the unique challenges faced by transport system managers in developing countries.
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The 'technical bible' for traffic engineers, the Austroads series Guide to Traffic Engineering Practice, has recently been replaced by three new Austroads guides: Guide to Road Design, Guide to Road Safety and Guide to Traffic Management. The new guidelines covering roundabouts now incorporate designs forthe marking of bicycle lanes in roundabouts, representing a change in technique to one not seen in comparable international guidelines. This paper examines the international research on bicycle lanes in roundabouts and considers whether the issues raised in the literature are applicable to Australia. It concludes that although overseas experience cannot be directly translated to Australia, the safety benefit of Australian cycle lane practice is clearly questionable. Good practice should be for any cycle measures to be well-designed and tailored to a particular roundabout, as part of a 'toolbox' of measures; but the new Austroads guides mean that it is more likely that cycle lanes will be the first (and quite possibly only) cycle measure considered. If so, this may well be at the cost of other, more effective measures (such as the C-roundabout design) that could also benefit other road users.
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Comparisons of crash frequencies often seek to establish how a country is performing relative to others in road safety experience. While such comparisons can be quite useful from a high-level management perspective, they are less useful in comparing the relative safety of roadway designs within and among countries at a road element (e.g. signalised intersection) level. This paper has been prepared with two fundamental objectives in mind. Comparisons of selected crash prediction models from New Zealand, North America, Sweden, Italy and Australia are made to: 1) illustrate how such comparisons might be used to learn lessons from differences in crash experience for similar roadway elements, and 2) illustrate how to assess the transferability of these models among jurisdictions (countries or states). The results show that it is possible to transfer models from one jurisdiction to the next. However, there are a number of differences between jurisdictions as a result of different reporting rates, design standards, speed limits and climate conditions that need to be accounted for when transferring models.
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Unsafe road crossing behavior by pedestrians is a main contributing factor of pedestrian casualties. Data from 2006 to 2012 in Delhi, India, show that pedestrians have the largest share in total road fatalities. Although facilities such as underpasses and overpasses are often provided to help cross a road, most often, pedestrians do not use them. Pedestrian perceptions play an important role in the use of such facilities. This study examined the relationship between actual crash risk and perceived risk for selecting crossing facilities by pedestrians. The road crossing preferences of pedestrians were analyzed for midblocks, intersections, and locations with a flyover where overpasses and underpasses are provided for road crossing. Responses covering safety and convenience of using specific facilities from one thousand pedestrians were collected through a structured questionnaire on selected locations. A path analysis model, i.e., a special case of structural equation modeling, was developed for analyzing the data. Results show that an inverse relationship exists between actual and perceived crash risks. Crossing behavior in midblocks was found to mediate this relationship. At locations with a flyover, the perspective of convenience was significantly related to the actual crash risk. This study identifies the potentially useful roles that pedestrian perceptions of risk and preferences in road crossing can play in avoiding actual crashes involving pedestrians. Pedestrians’ demographics was also analyzed with perceived risks and preferences for road crossing. From a policy standpoint, the relationships identified between actual and perceived risk and the built environment features of road crossing provide useful information for transportation planners, city planners and engineers. Since perceived risk influences travel behavior, it is important to study influence of perceived crash risk for pedestrians. Proactive interventions are required at the locations with low crash rates as the perceived risk by pedestrians is quite high at these places. This is in addition to the measures required at the locations associated with high actual crash risk faced by pedestrians though these locations are having low perceived crash risk.
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Over the last 15 years a multitude of accident prediction models have been developed for rural and urban intersections and mid-block sections in New Zealand. Although used extensively, the majority of these models focused on a limited set of features that were of interest at the time. There is a growing need for more comprehensive models, similar to those developed internationally. These comprehensive models uniquely partition the safety impacts of a range of road variables, allowing simultaneous assessment of a range of features. Such models provide better prediction of the expected crash risk associated with new or changed facilities, facilitate the identification of situations with abnormally high crash risk, allow more robust assessment of a range of potential solutions, and guide the development of design standards and policies. However, the limited size of the New Zealand road network and the associated data holdings means it will be difficult and or expensive to develop robust models. This paper discusses the latest research being undertaken, in conjunctions with a researcher in Canada, into the transferability of models between North America/Europe and NZ. It presents a discussion on the differences between the models produced in each countryand the likely factors that produce these differences. This note also discusses methods that have been developed elsewhere to transfer models between the different jurisdictions, and shows how such methods can be applied in New Zealand.
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Compact two-lane roundabouts are increasingly popular. Designing cycle lanes at two-lane roundabouts may not benefit motor vehicles, pedestrians and cyclists simultaneously. This study addresses environmental and operational aspects for accommodating bicycle treatments at compact two-lane roundabouts, namely: (i) sharing bicycles with the motor vehicle lanes; (ii) sharing bicycles with pedestrian pathways; (iii) dedicated bicycle lanes separated from pedestrian paths and motor vehicle lanes. Each scenario was subjected to different traffic, pedestrian and cyclist volumes. Using a microscopic traffic model, the operational performance of the above designs was compared. Then, a microscopic emission methodology based on vehicle-specific power and a semi-dynamic model were used to estimate pollutant emissions and traffic noise, respectively. It was found that cyclists travel time increased with the adoption of separated bicycle lanes since this design led to longer paths. However, average intersection travel time, emissions and noise decreased when compared to other designs.
Conference Paper
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The principal aim of this study is to develop a suitable model for predicting truck accidents at roundabouts and to identify the significance of the exposure variables (traffic and geometric characteristics) on truck accidents. To accomplish this, 70 roundabouts (with 284 approaches) were selected in the UK. The data used for model prediction included truck accidents, geometric, and traffic characteristics for whole roundabouts, within the circulatory lanes, and at approaches to roundabouts. General truck accident trends were identified for the selected roundabouts, and application of random parameters negative binomial (NB) count data models was used to estimate the influence of geometric and traffic characteristics on truck accidents and these are compared to the fixed-parameter NB models. Truck accidents account for 26% of all road accidents, but they account for more fatalities when compared to other types of vehicle accidents. Because of their size, load and manoeuvrability trucks account for more severe accident outcomes. The results indicate that random parameters models better fit the data compared to the fixed parameters models. Average annual daily traffic, percentage of truck traffic, approach grade type (grade separated /at-grade) are highly associated with increasing truck accidents; and three-arm roundabouts (as opposed to roundabouts with more entries), circulatory roadway width, and traffic signals (signalised/un-signalised) are associated with decreasing truck accidents at roundabouts. Keywords: Roundabouts, geometric characteristics, traffic characteristics, truck accidents, random-parameters.
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Pedestrian crashes are one of the major road safety problems in developing countries representing about 40% of total fatal crashes in low income countries. Despite the fact that many pedestrian crashes in these countries occur at unsignalized intersections such as roundabouts, studies focussing on this issue are limited—thus representing a critical research gap. The objective of this study is to develop safety performance functions for pedestrian crashes at modern roundabouts to identify significant roadway geometric, traffic and land use characteristics related to pedestrian safety. To establish the relationship between pedestrian crashes and various causal factors, detailed data including various forms of exposure, geometric and traffic characteristics, and spatial factors such as proximity to schools and proximity to drinking establishments were collected from a sample of 22 modern roundabouts in Addis Ababa, Ethiopia, representing about 56% of such roundabouts in Addis Ababa. To account for spatial correlation resulting from multiple observations at a roundabout, both the random effect Poisson (REP) and random effect Negative Binomial (RENB) regression models were estimated and compared. Model goodness of fit statistics reveal a marginally superior fit of the REP model compared to the RENB model of pedestrian crashes at roundabouts. Pedestrian crossing volume and the product of traffic volumes along major and minor road had significant and positive associations with pedestrian crashes at roundabouts. The presence of a public transport (bus/taxi) terminal beside a roundabout is associated with increased pedestrian crashes. While the maximum gradient of an approach road is negatively associated with pedestrian safety, the provision of a raised median along an approach appears to increase pedestrian safety at roundabouts. Remedial measures are identified for combating pedestrian safety problems at roundabouts in the context of a developing country.
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