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THE INTERMITTENT BUS LANE SYSTEM: DEMONSTRATION IN LISBON
... When regular vehicles are congested, yet the bus service frequency is low and bus lanes cannot be fully utilized, the DBL is seen to be an aggravating waste of road resources. To address this issue, Viegas and Lue [2,3] proposed the intermittent bus lane (IBL) method and provided a real-world demonstration in Lisbon as a prototype [4]. When the bus reaches upstream of the road section that is being allowed for dual use by buses and regular vehicles, one lane of the road section becomes dedicated to the bus. ...
... Accordingly, the estimated length-represented discharge capacity l d− max of the intersection in the bus lane can be obtained using equation (3). ...
Intermittent bus lanes (IBLs) can improve road capacity by allowing other regular vehicles to drive in the idle space of a dedicated bus lane. However, excessive vehicles in the IBL will cause additional bus delays. To avoid such problems, this study proposes a method to determine the capability of IBL permitted for regular vehicles first, and then use it as the total amount restriction of lane-borrowing vehicles to implement a bus lane control strategy that will improve road capacity and avoid additional bus delays. A model for calculating the capability of IBL is also provided. Vehicles between two buses are designated as potentially lane-borrowing vehicles that could follow the buses to leave the road section. The evolution process of these vehicles in the unit is analyzed using kinematic wave theory to obtain the formed traffic queue length. Using the rear bus trajectory to set the length limit on the traffic queue, the estimated total amount of lane-borrowing vehicles is corrected to establish the final capability of the IBL. The applicability of the method was evaluated from three perspectives: bus departure interval, road traffic saturation, and near-side bus stop. The simulation results showed that the proposed method can guarantee no additional bus delay compared to the situation of a dedicated bus lane. It can also improve road capacity more than traditional IBL under any degree of saturation and bus departure interval. Compared with traditional IBL, the average travel time of regular vehicles is shorter, except when the degree of saturation is high and the bus departure interval is large.
... The EBL priority measure grants buses an advantage in the network roads, while the signal-control based measures grant buses an advantage at the junctions. The concept of IBL for bus priority has been introduced as a means to combine the advantages of the two aforementioned measures, in an effort to provide permanent advantage to buses while imposing minimum losses for the remaining traffic [8,9]. IBLs are usually located on the rightmost lanes of the road, while some kind of variable light signals are placed on the road side along the line separating the IBL lane from the next [8]. ...
... Obviously, the vehicles moving in front of the bus inside the IBL can affect its movement and lead to an undesired speed reduction. However, for safety and stability reasons, IBL signals do not force existing vehicles to move away from the lane [8,9]. Therefore, to enable a bus to run through this lane with less delay, the IBL signals are switched on to allow an effective longitudinal (downstream) discharge of the vehicles that are driving on the IBL lane, and restrict, at the same time, any additional entry of general traffic from other lanes [8]. ...
In the years to come, public transport (PT) will be called to play a significant role towards achieving the sustainable transport system objective set for the future in Europe and beyond. To this end, the quality, accessibility and reliability of its operations should be improved. In this context, the favourable treatment of PT means within the road network may have, among others, a significant contribution. Such treatment can be derived as a result of an appropriate design of the road network facilities and/or the employed signal control at the network junctions. To this end, several approaches have been proposed, and it is the aim of this study to review the state-of-the-art and -practice in such approaches, focusing mainly on those attempting to provide priority via appropriate adjustment, in real time, of the junctions' signal control.
The paper provides an updated and improved version of the review undertaken and reported in the "Technical Report: Public Transport Priority in real time: A State-of-the-Art and Practice Review"
... It can also be seen from Figure 3.13 that only buses (in green), taxis (in blue) and charter buses (in blue) are allowed to travel on the curb lane of the upstream section. (Viegas, 2007), (Currie, 2008), and (Eichler, 2005). Viegas and Currie discuss implementations of intermittent bus lanes in Lisbon, Portugal and Melbourne, Australia, respectively. ...
A new type of dynamic bus lane not only ensures the strategy of bus priority but also significantly improves the spatiotemporal utilization of road resources and reduces the conflicting demands of buses and social vehicles on road resources. Firstly, the heterogeneity of bus arrival time is analysed according to the process of aggregation and dissipation of vehicle queues at intersections. Considering the correlation between the operating states of social vehicles and buses, a dynamic control strategy for bus lane based on the insertable interval of social vehicles is established. Secondly, combining the setting conditions of the intermittent bus lane control area with the correlation scenario of signal control at intersections and then according to the HCM 2010 vehicle delay equation and the BPR function, the associated optimized control model with the minimum total travel time consumption of the road section as the objective function is constructed. The global optimal control of the intermittent bus lane is realized through the computational experiment. Finally, the setting conditions and benefits of three lane organization schemes (including intersect (i.e., no bus priority), parallel, and intermittent bus lanes) are compared and analysed through case study. The results indicate that the intermittent priority bus lanes have opening hours, which can not only ensure bus priority but also expand the right way for social vehicles and make full use of road space resources, thus improving the overall traffic efficiency.
Bus lanes with intermittent priority (BLIPs) are lanes where general traffic is required to give way to approaching buses. BLIPs can improve the reliability of bus services and help maximize the use of road resources. It can be seen as an innovative sharing mobility, such as carsharing, carpooling, and lane sharing. However, implementation of BLIPs has never been feasible until vehicle communications could accommodate the idea. Vehicle-to-vehicle (V2V) communications have broad application prospects in the deployment of BLIPs. This paper develops a two-lane cellular automaton (CA) model to simulate BLIPs and assesses the benefits of connected vehicles for bus operation. In the model, lane-changings are asymmetric with an improved mandatory BLIP lane-changing rule underlying. The effects of BLIPs are explored through numerical simulations, including BLIPs’ impacts on neighboring lanes, travel time saving, fuel consumption, and the punctuality rate of buses. Analysis of traffic flow characteristics of corridors using BLIPs reveals that there is a strong connection among the bus departure interval, clear distance, and road capacity.
When compared to cars, public transportation (e.g., buses) can carry more people using less space. Hence, by increasing the share of people traveling by bus within an urban network, we can improve the efficiency of the urban transportation system, ultimately making it more sustainable. Unfortunately, buses operating mixed with cars can often get stuck in car congestion. One commonly used solution is to dedicate a lane for bus-use only. However, when bus flows are low, dedicated lanes running through intersections can reduce the discharge flows from these locations and lead to increased car delays, car queues, and all the negative externalities associated with congestion. This, in turn, can reduce the overall efficiency of the transportation network. Therefore, a solution is to discontinue the dedicated lane upstream of the main signal, removing bus priority at intersections. In this paper, we advocate the use of pre-signals upstream of signalized intersections to continue providing bus priority while minimizing the disruptions to car traffic. Pre-signals can allow buses to jump the car queues upstream of signalized intersections, while allowing cars to utilize the full capacity of the main signal when buses are not present. In this paper we provide practical guidelines on how to implement pre-signals at signalized intersections. Ideas on how to operate pre-signals are provided by using recent analytical and empirical findings from previous research on pre-signals. The reduction of system-wide (buses and cars) person hours of delay by using pre-signals, as compared to mixed-use lanes or dedicated bus lanes is also quantified. By doing so, the domains of application of pre-signals are also defined. This information can then be used to determine where and when pre-signals should be implemented in real urban networks and to quantify their benefits to the system.
SUMMARY As one of the most promising bus priority techniques, the innovative intermittent bus lane (IBL) strategy has drawn more attention in the past few years. In this paper, some improvements on the operation of the IBL strategy are proposed, and two cellular automaton models for a roadway section with two lanes, one with no bus priority and the other with an intermittent bus lane, are built to study the characteristics of urban traffic flow. Computer simulations and analytical models are developed to conduct quantitative research on the influence of IBL on the traffic density distribution, traffic velocity, and traffic capacity of the roadway section. By comparing the average paces in the two cases, this paper proposes a methodology to determine suitable traffic conditions for the IBL strategy implementation. The results indicate that for the designed scenarios, the IBL strategy is effective only when the traffic density is in the range of 25 to 74 pcu/km, which suggests that level of service C is the inflection point for implementing the IBL strategy. Copyright © 2014 John Wiley & Sons, Ltd.
In urban settings where space is at a premium, bus lanes can often times be created only via the conversion of existing general-use lanes. If buses are dispatched at low rates, the converted lanes will be under-utilized and squander road space. The bottlenecks within the city’s road network would then impart even greater delays to cars.The present paper addresses this problem by exploring novel ways in which buses and cars can share lanes within select bottlenecks. The details of a shared-lane strategy vary, depending upon certain details of its bottleneck. In all cases, the idea is to insert cars into a shared lane so as to put available road space to use without delaying buses. Ordinary lane conversions would occur elsewhere throughout the road network, and these would connect to the shared lanes within the bottlenecks.Analytical assessments unveil a wide range of cases for which the proposed strategies increase a bottleneck’s car-carrying capacity, as compared against reserving one of its lanes for buses only. Simulations of a real site indicate that significant reductions in car delays can result.
This synthesis provides a review of the application of a number of different transit preferential treatments in mixed traffic and offers insights into the decision-making process that can be applied in deciding which preferential treatment might be the most applicable in a particular location. The types of preferential treatments covered include median transitways, exclusive transit lanes, stop modifications, transit signal priority, special signal phasing, queue jump lanes, and curb extensions. The synthesis is offered as a primer on the topic area for use by transit agencies, as well as state, local, and metropolitan transportation, traffic, and planning agency staffs. This synthesis is based on the results from a survey of transit and traffic agencies related to transit preferential treatments on urban streets. Survey results were supplemented by a literature review of 23 documents and in-depth case studies of preferential treatments in four cities -- San Francisco, Seattle, Portland (Oregon), and Denver. Eighty urban area transit agencies and traffic engineering jurisdictions in the United States and Canada were contacted for survey information and 64 (80%) responded. One hundred and ninety-seven individual preferential treatments were reported on survey forms. In addition, San Francisco Muni identified 400 treatments just in its jurisdiction.
Segregated transit lanes are an efficient means of improving transit reliability and speed on shared urban roads. A major limitation of these lanes, however, is their impact on road capacity and traffic congestion. Intermittent bus lanes (IBL) are an innovative concept for addressing this limitation. IBLs include variable message signs and flashing lights embedded in the pavement that warn motorists to avoid transit lanes only when buses are coming. This approach prioritizes transit while limiting impacts on other road users. If feasible, this approach may substantially increase the scope of transit priority in cities. However, feasibility of IBL is a major concern. A trial was undertaken in Lisbon, Portugal, in 2005 and 2006. Although the results were promising, more practical experience with IBL is required to justify its widespread implementation. This paper reviews the performance of a variation on the IBL concept, the dynamic fairway (DF) adopted for trams in Melbourne, Australia. The system was initiated in 2001 and is still operational. The paper documents the world’s first practical, ongoing experience with IBL-DF operation. Future plans for a Melbourne bus-based IBL called the “moving bus lane” are also presented. Overall, the performance of the Lisbon IBL trial appears to be better than that of the Melbourne DF. However, the circumstances of the two examples were different, including the road configuration, transit mode, levels of congestion, and the newness of the technologies involved. Significantly, both applications found good driver compliance with transit lanes, suggesting the IBL-DF concept has practical performance benefits.
In many parts of the world concrete structures have failed due to Alkali-Aggregate Reaction (AAR). Researchers have explored remedial actions to be taken and mitigation techniques to be followed in concrete construction to alleviate the problem of AAR. In Sri Lanka, so far no documented evidence has been produced about investigations of this nature though there are a few old concrete structures which are still being used but showing symptoms similar in nature to AAR. To investigate the potential alkali-silica reactivity of Sri Lankan aggregates, preliminary work has been attempted. A quick chemical method which is used in many countries has been used to test fine and coarse aggregates collected from different locations in the country. According to the results, many aggregates can be placed in the non-reactive zone of the chart of innocuous and deleterious aggregates illustration of ASTM C 289. But some fall in a gray area close to the boundary of the demarcation of reactivity, which could be defined as a ‘slowly reactive’ zone. Having recognized the significance of quantifying the degree of reactivity of such slowly reactive aggregates, a new parameter called ‘potential reactivity index’ has been introduced. This index may serve the process of screening aggregates for structures of long life expectancies.
Bus priority at traffic signals is a growing area of cooperative transport system applications. Interest in bus priority continues to grow as the cities pay more attention to the needs of buses to provide fast, frequent, and reliable services, thus contributing to a sustainable transport system. Bus priority at traffic signals is particularly favored at places where road space is limited and traffic signal density is high. With increasing the use of automatic vehicle location (AVL) systems, it is now possible to provide “differential” priority, where different levels of priority can be awarded to buses at traffic signals according to chosen criteria (e.g., to improve regularity). At present, common strategies are based on the comparison of the time headway of a bus with the scheduled headway. However, this paper shows that greater regularity benefits could be achieved through a strategy where priority for a bus is based not only on its own headway but also the headway of the bus behind (the following bus). This paper demonstrates the benefits of this on a theoretical basis and quantifies the benefits from simulation modeling of a high-frequency bus route. Such a strategy provides an opportunity to exploit the more detailed location information available from the growing number of AVL-based systems for buses being implemented around the world.
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