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Vehicle mass as a determinant of fuel consumption and secondary safety performance: A comment
Abstract
One interaction between environmental and safety goals in transport is found within the vehicle fleet where fuel economy and secondary safety performance of individual vehicles impose conflicting requirements on vehicle mass from an individual’s perspective. Fleet characteristics influence the relationship between the environmental and safety outcomes of the fleet; the topic of this paper. Cross-sectional analysis of mass within the British fleet is used to estimate the partial effects of mass on the fuel consumption and secondary safety performance of vehicles. The results confirmed that fuel consumption increases as mass increases and is different for different combinations of fuel and transmission types. Additionally, increasing vehicle mass generally decreases the risk of injury to the driver of a given vehicle in the event of a crash. However, this relationship depends on the characteristics of the vehicle fleet, and in particular, is affected by changes in mass distribution within the fleet. We confirm that there is generally a trade-off in vehicle design between fuel economy and secondary safety performance imposed by mass. Cross-comparison of makes and models by model-specific effects reveal cases where this trade-off exists in other aspects of design. Although it is shown that mass imposes a trade-off in vehicle design between safety and fuel use, this does not necessarily mean that it imposes a trade-off between safety and environmental goals in the vehicle fleet as a whole because the secondary safety performance of a vehicle depends on both its own mass and the mass of the other vehicles with which it collides.
... Wenzel's work suggested that vehicle design, which can be improved by safety regulations, would be more effective on occupant safety than fuel economy standards that are structured to maintain vehicle size and weight (Wenzel, 2016). Tolouei and Titheridge (2009) warned that in vehicle design there is a trade-off between fuel economy and secondary safety performance imposed by mass. Even though mass imposes a trade-off in vehicle design, between safety and fuel use, it does not mean that it imposes a trade-off between safety and environmental goals in the vehicle fleet as a whole (Tolouei and Titheridge, 2009). ...
... Tolouei and Titheridge (2009) warned that in vehicle design there is a trade-off between fuel economy and secondary safety performance imposed by mass. Even though mass imposes a trade-off in vehicle design, between safety and fuel use, it does not mean that it imposes a trade-off between safety and environmental goals in the vehicle fleet as a whole (Tolouei and Titheridge, 2009). However other study suggested that there is almost no trade-off between better car safety and CO 2 emission reduction (Zachariadis, 2008). ...
... The previous research work showed that the safety and environmental trade-offs are still not fully explained and they impose a challenge for the transportation and environmental authorities. The few existing studies in the trade-off analysis (Chen and Ren, 2010; Wenzel, 2016; Tolouei and Titheridge, 2009; Zachariadis, 2008) have focused on the relationship between safety and fuel consumption, targeting CO 2 emissions only and discarding local pollutants such as: carbon monoxide (CO), nitrogen oxide (NO x ) and particle matter (PM), that have not been included in the analysis . Therefore, safety trade-offs analysis imposes still a challenge and the following questions can be risen. ...
... When cars were grouped by year of first registration rather than type, the driver of the older car tends to be at greater risk than the driver of the newer car (Broughton, 2008). More recently, Tolouei et al. (2009) showed that increasing vehicle mass generally decreases the risk of injury to the driver. ...
... When cars were grouped by year of first registration rather than type, the driver of the older car tends to be at greater risk than the driver of the newer car (Broughton, 2008). More recently, Tolouei et al. (2009) showed that increasing vehicle mass generally decreases the risk of injury to the driver. Previous studies related to crash analyses have used a broad spectrum of statistical models to reach conclusions. ...
This research explores the crash severity for the population of crashes resulting in injuries and/or fatalities. Real world crash data were collected from the Portuguese Police Republican National Guard records for the Porto metropolitan area, for the period 2006–2011.
The goal of this study is the development of a crash-severity prediction model with application to crash analysis and prevention. The target is a binary variable, FatalSIK (=1 for severe crashes, 0 otherwise). In this paper, the effect of vehicle characteristics, such as weight, engine size, wheelbase and registration year (age of vehicle) were analysed with data mining methodology in order to extract patterns from the predictors and relate them to the occurrence of injuries and fatalities in a crash.
A predictive approach using Classification and Regression Trees (CART) was adopted. To conduct the analysis with high unbalanced data, oversampling followed by correction of prior probabilities for the original crash population was applied. For all crashes, the Weight of the Vehicle was the most important variable for tree split, and those crashes involving weight≥1743.5 kg were the most severe, (χ ² p value<0.1382). For two vehicle crashes, weight was also the most important variable, followed by Speed. The highest percentage of severe crashes occurred in collisions involving heavier vehicles and in routes with higher speed, (χ ² p value<0.0017). For the single vehicle crashes, the highest percentage of severe crashes involving a vehicles with a larger engine size (ccV1≥1588 cm ³ ) and those that were older (AgeV1≥4.5), (χ ² p value<0.056).
... Depending on the engine efficiency of a vehicle and the energy required by vehicle accessories †, a certain amount of fuel energy is consumed to overcome forces resisting vehicle motion during a driving cycle; this is strongly influenced by vehicle mass. In a previous study, the isolated effects of vehicle mass and other design features on vehicle fuel consumption were estimated using disaggregate statistical modelling of fuel consumption and vehicle design data (Tolouei and Titheridge, 2009). The data used was based on officially certified fuel consumption rates for specific makes and models, which are measured under controlled driving cycles, vehicle condition and ambient temperature. ...
One potential interaction between environmental and safety goals in transport is found within the vehicle fleet where fuel economy and safety impose conflicting requirements on vehicle design. Larger and heavier vehicles have a better secondary safety performance during a crash. On the other hand, they are associated with higher levels of fuel consumption and carbon emissions. This issue has generated debate amongst researchers and policy makers when formulating policies to improve the environmental performance of the road transport system. This research investigates the safety consequences of changes in vehicles mass within the vehicle fleet aimed at increasing fleet fuel economy. The estimated relationships between vehicle design, particularly mass, and each of carbon emissions and safety performance were used to investigate partial safety and environmental effects of changes in mass distribution within the fleet using an incremental approach. Results generally showed that the relationship between carbon emission and safety performance in vehicle design depends on the characteristics of the vehicle fleet, and in particular, mass distribution. It was shown that an informed change in the mass distribution not only imposes no trade-off between the fuel economy and safety goals, but also could lead to a desirable outcome in both aspects.
... Work from Saboohi and Farzaneh (2009) underlines three potentially important factors behind these kinds of routing preferences: (1) driver behaviour; (2) the relationship between fuel consumption, speed, and gear ratio; and (3) the impact of engine load on fuel consumption. Meanwhile, other studies observe vehicle mass can also affect fuel consumption (Tolouei and Titheridge, 2009). But while much of the literature has looked at these factors in densely populated urban areas, these studies have not been linked to paratransit. ...
In developing countries, paratransit often meets essential mobility needs with older, inefficient vehicles that degrade air quality and emit greenhouse gases (GHGs). International climate change finance mechanisms such as the Clean Development Mechanism (CDM) or Green Climate Fund (GCF) could help fund cleaner vehicles. However, these mechanisms require generating a credible business-as-usual GHG baseline to compare against actual emissions. For paratransit, irregular scheduling and erratic driving behaviour add to a well-documented list of factors that make the transaction costs prohibitively expensive for constructing robust transport baselines. This paper compares the relative accuracy and affordability of constructing five baselines for motorcycle taxis or ojeks in Bandung, Indonesia. The baselines that were constructed incorporate data that was gathered from one day and one week studies using revealed preference surveys as well as using real time global positioning systems (GPS) over one week into fuel efficiency and fuel consumption-based emissions calculation techniques. The calculations show that the week-long fuel consumption survey data generated the lowest fuel efficiency and highest GHG estimates. Driver survey data may therefore help construct a relatively low cost conservative baseline, especially when triangulated by GPS-verified distance travelled data. The study concludes with several promising future research areas, including expanding the period of estimation for paratransit; examining the relationship between self-reported distance and fuel consumption data; optimizing survey administration; and promoting climate finance mechanisms that engage stakeholders to lower the transaction costs of data gathering.
... In general, EVs are heavier than ICEVs due to the electric engine and batteries, although this is partially overcome by the decrease in weight due to the absence of a combustion engine and tank. Increases in vehicle mass have a determining impact on fuel consumption (Burgess and Choi, 2003; Tolouei and Titheridge, 2009), and this factor must be included in the model. According to the vehicle comparison presented in Thiel et al. (2010), EVs can be considered to be, on average, 185 kg heavier than diesel ICEVs. ...
... rontal area and aerodynamic drag coefficient. Vehicle weight is the most significant parameter affecting vehicle energy consumption from vehicle loads (Burgess & Choi, 2003). The results obtained by Fontaras & Samaras (2010) for an NEDC cycle, showed that a 10% reduction in vehicle mass could allow CO 2 emissions reduction ranging from 2.7 to 3.6%. Tolouei & Titheridge (2009) showed that the effects of mass on fuel consumption are more important for extra-urban driving cycles than for urban-driving cycles. These reductions may be achieved by the use of lightweight materials, for example. However, making assumptions over the possible gains coming from reducing vehicle mass without considering the effects that ...
Road transport largely dominates the transportation demand and energy consumption. Passenger light-duty vehicles (passenger cars and light trucks) are responsible for almost half of the energy consumption of road transport. This energy is mainly supplied by fuels produced using oil resources, increasingly difficult and expensive to exploit. The use of these fuels also generates greenhouse gases, mainly carbon dioxide. This paper analyzes and compares strategies from different domains – the vehicle, the driver and the environment – for reducing carbon dioxide emissions from the use phase of passenger cars. These strategies represent one step towards climate change mitigation and sustainable mobility growth. A framework for classifying these strategies and the interactions between measures coming from different domains is proposed. The results highlight the possibilities of integration between domains that remain unexplored and that could bring significant gains in terms of emissions reductions.
... Amongst various vehicle design features, vehicle mass is a key variable from a policy perspective because of its effect on fuel consumption and emissions on the one hand, and its effect on safety performance of vehicles within the fleet on the other hand. A decrease in mass of the vehicles within the fleet is associated with a decrease in overall fuel consumption and emissions (Tolouei and Titheridge, 2009); however, the effect of vehicle mass on safety is more complicated. While it is generally accepted that decreasing the mass of a vehicle, all other factors being constant, imposes a greater risk of injury to its occupants when the vehicle is involved in a crash, it is not clear what effect a change in the distribution of vehicles' mass within a fleet has on the overall safety of the fleet. ...
This paper introduces a novel methodology based on disaggregate analysis of two-car crash data to estimate the partial effects of mass, through the velocity change, on absolute driver injury risk in each of the vehicles involved in the crash when absolute injury risk is defined as the probability of injury when the vehicle is involved in a two-car crash. The novel aspect of the introduced methodology is in providing a solution to the issue of lack of data on the speed of vehicles prior to the crash, which is required to calculate the velocity change, as well as a solution to the issue of lack of information on non-injury two-car crashes in national accident data. These issues have often led to focussing on relative measures of injury risk that are not independent of risk in the colliding cars. Furthermore, the introduced methodology is used to investigate whether there is any effect of vehicle size above and beyond that of mass ratio, and whether there are any effects associated with the gender and age of the drivers. The methodology was used to analyse two-car crashes to investigate the partial effects of vehicle mass and size on absolute driver injury risk. The results confirmed that in a two-car collision, vehicle mass has a protective effect on its own driver injury risk and an aggressive effect on the driver injury risk of the colliding vehicle. The results also confirmed that there is a protective effect of vehicle size above and beyond that of vehicle mass for frontal and front to side collisions.
... ed the heavier the cars are. The external risk of the heaviest cars was found to be about 75% higher than the external risk of the lightest cars. Finally, the total number of injured persons was almost independent of car mass. These results suggest that the increase in the external risk with increasing weight might offset the gain in internal risk. Tolouei and Titheridge (2009) also pointed out that the distribution of mass within the fleet and other fleet characteristics are important factors in determining the relationship between mass and safety performance of vehicles. Folkhälsan (2010) showed that the safety gap between large and small cars has decreased in terms of risk for fatality or permanent disabili ...
Purpose
This study examined interactions of environmental and safety measures for road transportation.
Method
Road-safety effects of various measures targeting environmental problems of road transportation and environmental effects of various road-safety measures were reviewed.
Results
The results showed that a vast majority of the examined measures support both policy objectives and thereby contribute effectively to sustainable transportation. However, there were also measures with conflicting effects, although the number of those measures was limited. In addition, there were a number of measures with no interaction. Furthermore, many potential effects were not documented and therefore in many instances only likely effects were noted.
Conclusion
There are two practical implications of this study. First, those measures that result in double benefits should be encouraged to be implemented. Second, in case of conflicting measures, the specific implementations should attempt to minimize the negative effects.
The role of intermediate-volatility and semi-volatile organic compounds (I/SVOCs) in heavy-duty diesel vehicle (HDDV) exhaust remains a significant research gap in previous studies, with limited focus on cumulative mileage and ambient temperature effects. This study analyzed gaseous and particulate I/SVOCs from four in-use HDDVs using thermal desorption two-dimensional gas chromatography–mass spectrometry (TD–GC × GC–MS). The total I/SVOC emission factors (EFs) ranged from 9 to 406 mg km⁻¹, with 79 %–99 % in the gaseous phase. High-mileage vehicles (HMVs) emitted I/SVOCs at levels 8 times greater than low-mileage vehicles (LMVs), highlighting the influence of cumulative mileage. Emission deterioration occurred under both cold-start and hot-running conditions, though HMVs showed no extra sensitivity to cold starts. HMVs also exhibited increasing emissions with component volatility, alongside a higher proportion of oxygenated I/SVOCs (O-I/SVOCs) than LMVs (65 % vs. 42 %). Unique compounds such as phenol, alkenes, and cycloalkanes were detected exclusively in HMV emissions. Temperature effects were most pronounced at 0 °C, where only HMV emissions increased significantly, while LMV emissions remained relatively stable. A strong linear correlation (R2= 0.93) between I/SVOC EFs and modified combustion efficiency (MCE) suggested that reduced combustion efficiency is a key driver of higher I/SVOC emissions. HMVs also showed 4 times greater secondary organic aerosol formation potential (SOAFP) compared to LMVs. This increase was smaller than the 8-fold rise in EFs, likely due to the higher O-I/SVOC content in HMV emissions.
In this investigation, a thermodynamic study was performed to predict the type and amount of possible oxides formed on interstitial-free high-strength (IFHS) steel substrate surface during the annealing treatment prior to dipping in a liquid zinc alloy bath. This study was carried out based on CALPHAD approach using the thermodynamic simulation software package Thermo-Calc by varying the annealing temperature and annealing atmosphere (dew point and gas composition). The experiments were performed on IFHS-350 grade steel substrate using hot-dip process simulator (HDPS) for varying annealing conditions (temperature: 780–830 °C and dew point: − 30 to + 10 °C). The specimens were characterized in as-annealed condition as well as after hot dipping in the galvanizing bath. This investigation was performed to find out the suitable combinations of annealing temperature and dew point for developing a good quality coating on IFHS grade steel substrate by eliminating the wettability issues. Good quality coating, free from bare spots, was obtained using an annealing gas atmosphere having 5%H2 and 95%N2 at (a) 780 °C with − 30 °C dew point, (b) 805 °C with − 10 °C dew point and (c) 830 °C with + 10 °C dew point. In general, coating quality was improved with low annealing temperatures and low dew point or high annealing temperature and high dew point conditions.
Introduction. The current methodology for fuel consumption accounting in road vehicles has not been changed in terms of its quality for a long time. In the majority of transport enterprises of the Cheliabinsk Region, official methods for the regulation of fuel consumption are not used, which indicates the need to improve the fuel consumption accounting standards. The most significant differences between standardized and real consumption are related to transport work.
Purpose of the experiment . The article aims to carry out a statistical analysis of the influence of cargo weight on fuel consumption in long-distance transport.
Results of the experiment . In order to identify the dependence of cargo weight on fuel consumption in longdistance transport, a study is conducted on the statistical data on the operation of truck tractors at OOO Alliance Auto, one of the largest long-distance road carriers in the Cheliabinsk Region. The study is conducted on MercedesBenz Actros-1840 truck tractors equipped with fuel consumption monitoring devices and devices for determining axle loads. The cargo weigh is determined by subtracting the curb weight from the actual one according to the axle load data. Data on the values of the actual cargo weight and fuel consumption for each trip are recorded using the Fleet Board software and hardware complex; Excel and STATISTICA programs are used to calculate and construct the necessary graphs and regression equations. The statistical analysis performed makes it possible to establish the nature and indicators of the dependence of fuel consumption on cargo weight in long-distance transport. As a result, the relationship between the flow rate and the cargo weight is established; a confidence test is performed; and a regression equation is obtained.
Conclusion. Analysis of the collected data shows that the dependence of fuel consumption for transport work by road trains with truck tractors Mercedes-Benz Actros-1840 on the cargo weight for the Russian operating conditions in long-distance transport is linear and amounts to 0.39 liters per 100 km for each ton of transported cargo.
Hot-rolled high strength steel with ferrite matrix and nano-size precipitation is one of the novel advanced ferrous grades at present. This grade of steel, namely NPS800 (Nano-precipitation strengthened 800 grade) finds application in automobile industry for the manufacture of long member parts of large-capacity vehicles. Apart from the minimum strength level of 800 MPa and ductility over 16%, the steel requires adequate stretch flangeability to prevent a catastrophic failure in service. While the grade achieved the desired tensile strength and ductility as per the stipulated specification, there were incidences of erratic stretch flangeability. Detailed microstructural characterization has been carried out to explore the reasons for variations in stretch flangeability. The study reveals that there is a direct correlation between nature of precipitate distribution and size with stretch flangeability. Pre-dominant interphase-controlled precipitation below ~ 12 nm average size is desirable to obtain desired stretch flangeability. To achieve the typical characteristic of precipitation, Ti/Mo atomic ratio plays an important role.
Hot-rolled high-strength steel having ferrite matrix and nano-size precipitation possesses a good combination of strength and ductility, and it finds application in the automobile industry for the manufacture of long member and chassis parts of large-capacity vehicles. Such an application needs steel with high stretch flangeability since there are several drilled or broached holes in the finished component. Apart from an adequate strength level of 800 MPa UTS with a minimum elongation of around 16%, the steel requires a high degree of stretch flangeability to avoid any catastrophic failure during its use. During the commercial production process, sometimes, the steel grade namely NPS800 (Nano-Precipitation Strengthened 800 grade) exhibited brittle fracture in the tensile test specimens as well as during the component manufacture. A detailed study was undertaken to understand the causes of brittle fracture or mixed-mode fracture, despite the steel showing a total elongation of not less than 18%, and the resolution to this problem is explained in this paper. Despite the steel having tensile strength and total elongation as per specification, the performance of steel during component forming was found to be erratic. The steel samples while possessing similar chemical composition and mechanical properties exhibited a variation in stretch formability. The main strengthening mechanism of this new grade being precipitation hardening by nano-precipitates, a detailed study involving microstructural characterization became essential to explain the causes of the incidences of poor stretch flangeability. Our study reveals that the size distribution of nano-precipitate formed at the austenite–ferrite interfaces plays an important role in determining the steel properties such as strength, strain-hardening exponent, stretch flangeability, uniform elongation and post-necking elongation. For the normal finish rolling and coiling temperatures, optimization of chemistry was achieved to obtain the mechanical properties such as strength and ductility in the desired range. It is observed that the fineness of the nano-precipitate is important to achieving a good combination of strength, total elongation, strain-hardening exponent, and post-necking elongation to obtain satisfactory stretch formability. The study on the crack tip opening displacement (CTOD) also confirms the significance of finer precipitates on crack propagation and thereby improving hole expansion ratio (HER). By the study of fracture samples using transmission electron microscopy, the role of large-size precipitates in causing the mixed-mode or brittle failure is explained. The significance of the reduction in area (RA), post-necking elongation, and strain rate sensitivity in achieving a satisfactory HER is established.
In recent years, the demand for advanced high-strength steel (AHSS) has increased to improve the durability and service life of steel structures. The development of these steels involves innovative processing technologies and steel alloy design concepts. Joining these steels is predominantly conducted by following fusion welding techniques, such as gas metal arc welding, tungsten inert gas welding, and laser welding. These fusion welding techniques often lead to a loss of mechanical properties due to the weld thermal cycles in the heat-affected zone (HAZ) and the deposited filler wire chemistry. This review paper elucidates the current studies on the state-of-the-art of weldability on AHSS, with ultimate strength levels above 800 MPa. The effects of alloy designs on the HAZ softening, microstructure evolution, and the mechanical properties of the weld joints corresponding to different welding techniques and filler wire chemistry are discussed. More specifically, the fusion welding techniques used for the welding of AHSS were summarized. This review article gives an insight into the issues while selecting a particular fusion welding technique for the welding of AHSS.
Speed is a major risk factor in overall road safety performance. The objective of this study was to identify the most frequent explanatory variables and measures used to investigate the speed factor contribution to crash injury risk (CIR). For this purpose, a literature oriented approach was used. The analysis review, underpinned by data collected from 64 journal publications reported over the past 21 years shows that speed limit was the most frequently used variable selected by the authors to investigate speed contribution CIR. Following, speed delta-V was the second most used variable, despite the barriers to access in-depth crash quality data. Even so, the speed limit was used 3.5 times more than delta-V, possibly due to the facilitate accessibility to the roads standardize posted speed limits. However, it is unknown how much vehicles travel speed could deviate from the posted speed limit at the moment of the crash.
This research was derived from the experimental observation that hydraulic actuators are positioned on machines that are subjected to movements and whose dynamic actions, the accelerations, are very high; it is acceptable to think of an actuator for an anthropomorphic robot. From this point of view, the weight of the actuator plays a fundamental role in the performance of the machine. In order to face this problem, a real hydraulic cylinder has been designed (for use on an earth moving machine) both analytically (adopting the theories of continuous mechanics) and numerically through finite element analysis. The results obtained were then generalized by determining functions that in relation to specific values of the variables, such as working pressure, allow one to determine the minimum weight of the component and its geometric configuration. The functions also made it possible to identify the most significant contributions to the overall weight of the component and therefore the elements on which to focus the subsequent lightening process. In particular, the greatest contribution is made by obtaining relations that are completely general and therefore adaptable to different case studies.
A preliminary study on a double-acting hydraulic cylinder subject to high-pressure loading conditions (pressure = 350 bar) and with a bore diameter of 300 mm is presented. The substitution of the reference steel cylinder tube with a multi-material tube is investigated. In detail, a solution providing a steel thin inner liner wrapped by carbon composite materials is analytically and numerically tested in terms of weight reduction. The composite lay-up design and the component geometry are built to comply with manufacturing constraints for a relatively high-volume production. The alternative multi-material cylinder is designed to ensure the same expected performance as its steel counterpart. Firstly, the non-conventional hydraulic cylinder was designed by extending Lamé’s solution to composite materials, by adopting the micro-mechanics theory of composites in order to bear the maximum operating pressure by monitoring its radial and axial deformation. The selection of the most appropriate carbon reinforcement was investigated. The influence of the stiffness-to-weight and the strength-to-weight ratio of the reinforcement on the design is discussed. Secondly, finite element analyses were performed to evaluate the occurrence of buckling and the modal response of the actuator considering the fluid and of the cylinder own weight influence. The results confirm the validity of the new cylinder tube design compared to the reference steel component. The proposed barrel weights 80 kg compared to the 407 kg of the reference cylinder, with a weight reduction of ~80%. Furthermore, it has a compact design with a decrease of the barrel outer diameter of ~5.3%.
Abstract
Taxis are considered one of the symbols of urban transportation systems due to their large daily traveling mileage. Taking into account hatchback cars with two rows of seats, this paper presents a new approach to taxi efficiency by decreasing the vehicle size. The policy’s influences on fuel consumption, emission, safety, and economic efficiency are comprehensively analyzed. With supplementary surveys of taxi passengers, a total of 1110 taxi trips are observed at nine busy locations. The results show that the trunk is not used in 88% of taxi trips in Hangzhou. It is estimated that downsizing each taxi results in annual decreases in fuel consumption by 1600 L, CO by 311.9 kg, HC by 15.4 kg, and NOx by 8.9 kg. By using a small car as a taxi instead of a standard car, the annual fixed cost plus the fuel cost will be reduced by 38%. By analyzing GPS data of 7081 taxis in Hangzhou, we found a network-wide average taxi speed of 23 km/h. Since the average speed of taxis is relatively low in urban areas, the use of small cars could provide drivers with higher maneuver capability, while increasing the safety of small cars. According to the findings of this paper, using small cars will increase the efficiency and sustainability of the taxi industry. View Full-Text
Keywords: taxi downsizing; sustainability; GPS data; fuel consumption; emission; economic efficiency
Hot stamping (HS) process is a new technology for fabricating high-strength aluminum alloy. In order to improve the formability of materials in the forming process, a new hot stamping process with pre-cooling (HSPC) is proposed in this paper. By adding a pre-cooling stage between the solid solution and the forming, the strain hardening exponent (SHE) could be increased due to the decreasing of the forming temperature, and the uniform deformation ability could be improved. In the HSPC of 7075 aluminum alloy, the blanks exhibited two pre-cooling modes: air cooling pre-cooling (ACPC) and cold iron pre-cooling (CIPC). The effects of pre-cooling rate and temperature on the microstructure and mechanical properties of formed parts were studied. The results showed that when the pre-cooling temperature was 300 °C by CIPC, the formed parts had the smallest thickness thinning and the best mechanical properties after aging. Compared with ACPC, CIPC had less precipitation during quenching, which ensured good subsequent aging strengthening effect.
Transit bus passenger loading changes significantly over the course of a workday. Therefore, time-varying vehicle mass as a result of passenger load becomes an important factor in instantaneous energy consumption. Battery-powered electric transit buses have restricted range and longer “fueling” time compared with conventional diesel-powered buses; thus, it is critical to know how much energy they require. Our previous work has shown that instantaneous transit bus mass can be obtained by measuring the pressure in the vehicle’s airbag suspension system. This paper leverages this novel technique to determine the impact of time-varying mass on energy consumption. Sixty-five days of velocity and mass data were collected from in-use transit buses operating on routes in the Twin Cities, MN metropolitan area. The simulation tool Future Automotive Systems Technology Simulator was modified to allow both velocity and mass as time-dependent inputs. This tool was then used to model an electrified and conventional bus on the same routes and determine the energy use of each bus. Results showed that the kinetic intensity varied from 0.27 to 4.69 mi⁻¹ and passenger loading ranged from 2 to 21 passengers. Simulation results showed that energy consumption for both buses increased with increasing vehicle mass. The simulation also indicated that passenger loading has a greater impact on energy consumption for conventional buses than for electric buses owing to the electric bus’s ability to recapture energy. This work shows that measuring and analyzing real-time passenger loading is advantageous for determining the energy used by electric and conventional diesel buses.
Firstly, this paper summarizes the characteristics of vehicle running characteristics and design parameters, which have influence on vehicle fuel consumption. Secondly, 200 vehicle’s test results are used as training samples, with sensitive features and fuel consumption of type approve test as the input parameters, and the actual vehicle fuel consumption as output parameters. Then, a vehicle fuel consumption prediction model, which is based on least squares support vector machine, is established. Finally, the vehicle fuel consumption prediction model is used to predict the fuel consumption of another 100 vehicles. The results show that the prediction error of the test samples are less than 5%, and the fuel consumption prediction model proposed in this paper has fully considered the impact of vehicle operating characteristics and design parameters on fuel consumption. In addition, the fuel consumption prediction model has high prediction accuracy and reliability than some traditional methods such as backpropagation neural network (BPNN).
Traffic source emission inventories for the rapidly growing West African urban cities are necessary for better characterization of local vehicle emissions released into the atmosphere of these cities. This study is based on local field measurements in Yopougon (Abidjan, Côte d’Ivoire) in 2016; a site representative of anthropogenic activities in West African cities. The measurements provided data on vehicle type and age, traveling time, fuel type, and estimated amount of fuel consumption. The data revealed high traffic flow of personal cars on highways, boulevards, and backstreets, whereas high flows of intra-communal sedan taxis were observed on main and secondary roads. In addition, the highest daily fuel consumption value of 56 L·day−1 was recorded for heavy vehicles, while the lowest value of 15 L·day−1 was recorded for personal cars using gasoline. This study is important for the improvement of uncertainties related to the different databases used to estimate emissions either in national or international reports. This work provides useful information for future studies on urban air quality, climate, and health impact assessments in African cities. It may also be useful for policy makers to support implementation of emission reduction policies in West African cities.
The ongoing development driven by the progression of technology and science is leading to enhanced energy consumption. Most of the in-use energies are from restricted fossil fuel and most of the fossil fuel consumers are spark-ignition engines. On the other hand, the main duty of the development engineer is to decrease cost and increase power output and trustworthiness of an engine. In trying to succeed in these goals, they have to try out different design concepts. Hence, the objective of this study is to investigate the effect of oxygen additive in intake of fuel consumption, brake torque, and brake power as a new way to increase the performance of the spark-ignition engine. In order to effectively increase brake torque and brake power, the percentage of oxygen content in air was changed. The engine’s performance characteristics under various engine speeds and oxygen concentrations were measured. The experimental results showed that the brake torque output, brake power output, and fuel consumption were increased significantly by increasing the oxygen concentration at the intake. Finally, it is found that oxygenating the air causes to increase the performance on spark-ignition gasoline engine.
Climate change is receiving increasing attention in recent years. The transportation sector contributes substantially to increased fuel consumption, greenhouse gas (GHG) emissions, and poor air quality, which imposes a serious respiratory health hazard. Road transport has made a significant contribution to this effect. Consequently, many countries have attempted to mitigate climate change using various strategies. This study analysed and compared the number of policies and other approaches necessary to achieve reduced fuel consumption and carbon emission. Frequency aggregation indicates that the mitigation policies associated with driving behaviours adopted to curtail this consumption and decrease hazardous emissions, as well as a safety enhancement. Furthermore, car-sharing/carpooling was the least investigated approach to establish its influence on mitigation of climate change. Additionally, the influence of such driving behaviours as acceleration/deceleration and the compliance to speed limits on each approach was discussed. Other driving behaviours, such as gear shifting, compliance to traffic laws, choice of route, and idling and braking style, were also discussed. Likewise, the influence of aggression, anxiety, and motivation on driving behaviour of motorists was highlighted. The research determined that driving behaviours can lead to new adaptive driving behaviours and, thus, cause a significant decrease of vehicle fuel consumption and CO2 emissions.
Automobile development is a complex system engineering with multi-objective coupling. Setting an accurate mass target to ensure the vehicle performance is the chief work of the vehicle mass development. This article analyzes key characteristic parameters which relate to vehicle mass from the aspect of customer needs and mapping relation between key characteristic parameters and vehicle mass through statistical analysis based on the vehicle mass data of benchmark cars. To meet the requirement of different development indexes and to ensure the vehicle performance, the impact of each characteristic parameter on the mass target is determined through analytic hierarchy process (AHP) and quality function deployment (QFD) methods. Finally, this article develops mass target setting model and puts forward a new method and application steps of setting vehicle mass target. Through practical usage, the new method can ensure the vehicle performance, and increase the accuracy and reliability of mass target. Besides, the method makes the vehicle mass development more knowledgeable and agile.
The automotive industry is facing many problem at a present day, but a possible way to overcome these limitations can be a green approach. Besides the most advertised ways of reducing pollutant emission, i.e. changing the fuels, vehicle mass can be reduced to reach the same objective. In this paper, a methodology to reduce the weight of an automotive hood substructure is presented. The methodology consists in a loop of different optimization techniques, i.e. topology, topometry, size and topography, coupled with a constant re-designing of the model. Without breaking the performance targets expected by Ferrari internal regulation, the mass has been reduced respecting manufacturing constrain.
In recent years, a new class of compact vehicles has been emerging and wide-spreading all around Europe: the quadricycle. These four-wheeled motor vehicles, originally derived from motorcycles, are a small and fuel-efficient mean of transportation used in rural or urban areas as an alternative to motorbikes or city cars. In some countries, they are also endorsed by local authorities and institutions which support small and environmentally-friendly vehicles. In this paper, several general considerations on quadricycles will be provided including the vehicle classification, evolution of regulations (as homologation, driver licence, emissions, etc), technical characteristics, safety requirements, most relevant investigations, and other additional useful information (e.g. references, links). It represents an important and actual topic of investigation for designers and manufacturers considering that the new EU regulation on the approval and market surveillance of quadricycles will soon enter in force providing conclusive requirements for functional safety environmental protection of these promising vehicles.
The main goal of this research was to develop models for crash severity prediction in a subject vehicle while taking into account the impact of both vehicles involved (Vehicles V1 and V2). Three binary targets were modeled: FataISIK (to predict overall severity), FataISIKV1 (to predict the probability of a serious injury, fatality, or both in Vehicle V1), and FatalSIKV2 (to predict the probability of a serious injury, fatality, or both in Vehicle V2). For the period from 2006 to 2010, 874 collisions involving injuries, fatalities, or both were analyzed. However, the crash sample included few severe events. Because imbalanced data introduce a bias toward the majority class (nonsevere crashes), in predictive modeling, they would result in less accurate predictions of the minority class (severe crashes). For the challenge imposed by small sample size and imbalanced data to be overcome, an important methodology was developed on the basis of a resampling strategy by using 10 stratified random samples for model evaluation. The effect of vehicle characteristics such as weight, engine size, wheelbase, and registration year (age of vehicle) were explored. Logistic regression analysis for FataISIK suggested that the age of the vehicle and the type of collision were significant predictors (p < .0084 and .0346, respectively). Models FataISIKV1 and FatalSIKV2 showed that the engine size of the opponent vehicle was statistically significant in predicting severity (p < .0762 and p < .03875, respectively). Models for FataISIKV1 and FatalSIKV2 yielded satisfactory results when evaluated with the 10 stratified random samples: 61.2% [standard deviation (SD) = 2.4] and 61.4% (SD = 3.1), respectively.
Dump trucks are used for transportation in opencast mines and consume about 32% of the total energy use in mines. This paper presents a generic model to benchmark energy consumption for dump trucks in mines. The modelling framework estimates minimum specific fuel consumption (SFC) of dump trucks using mine equipment, engine characteristics and vehicle dynamics. The model investigates the variation of SFC with operating input parameters like payload, material handling rate, vehicle speed, distance, mine gradient, etc. The applicability of the proposed model is illustrated through a case study of multiple dump trucks in a down gradient opencast limestone mine in India. The minimum SFC of 89 g/t is estimated for a mine transport system with three excavators and two crushers. The case study shows a potential fuel saving of 17%. The modelling framework developed can be used to set rational targets for energy consumption for dump trucks in mines.
The current emissions regulations lead car manufacturers to look carefully for weight reduction. In the automotive industry the classic trial-and-error approach to design is becoming inadequate and techniques based on optimization are necessary to improve the design process. In this study a methodology to design a sport-car front hood is proposed. The process carried out could also be extended to car components characterised by a similar configuration.
Starting from the geometry of the actual part, a design volume has been defined. The first step consists of a topology optimization performed considering the material as isotropic (aluminium properties): the output is a rough structure which accomplishes all the imposed targets. The interpretation of the topology results brings to a re-design phase aimed at realising a feasible component.
The subsequent optimization step is dedicated to composite material structures and acts on the component plybook, varying thickness and orientation of each ply to find the best solution complying with targets. Finally, the component has to be reviewed from a technological point of view in order to be virtually delivered and to proceed with the prototype phase.
The present study conducts a vehicle dynamic modeling of gasoline and diesel vehicles by using the AVL commercial program. 10 passenger vehicles were tested for 7 types of driving modes containing city, express and highway driving mode. The various vehicle data (specifications, fuel consumption map, gear shifting curve data, etc.) were collected and implemented as input data. The calculations were conducted with changing driving modes and vehicle types, and prediction accuracy of the calculation results were validated based on chassis dynamometer test data. In order to increase prediction accuracy for a wide vehicle operating range, some modifications regarding gear shifting was also conducted. From these processes, it is confirmed that the prediction accuracy of fuel efficiency and CO2 emissions shows a strong correlations with test results. After ensuring the accuracy of the calculation result, parametric studies were conducted to reveal correlations between vehicle specifications (e.g., vehicle weight and frontal area) on fuel efficiency and CO2 emissions and check which parameters were highly impact on fuel efficiency.
Attention is called to evidence that in collisions between vehicles of equal mass, and in single-vehicle collisions, there is unlikely to be a very strong effect of car size on injury severity, and that variation in crashworthiness within the set of car models of a given size has a much larger effect. Consequently, the secondary safety of a national fleet of small cars in the future could be as high as that of a national fleet of large cars today.
By identifying energy waste streams in vehicles fuel consumption and introducing the concept of lean driving systems, a technological gap for reducing fuel consumption was identified. This paper proposes a solution to overcome this gap, through a modular vehicle architecture aligned with driving patterns. It does not address detailed technological solutions; instead it models the potential effects in fuel consumption through a modular concept of a vehicle and quantifies their dependence on vehicle design parameters (manifesting as the vehicle mass) and user behavior parameters (driving patterns manifesting as the use of a modular car in lighter and heavier mode, in urban and highway cycles). Modularity has been functionally applied in automotive industry as manufacture and assembly management strategies; here it is thought as a product development strategy for flexibility in use, driven by environmental concerns and enabled by social behaviors. The authors argue this concept is a step forward in combining technological solutions and social behavior, of which eco-driving is a vivid example, and potentially evolutionary to a lean, more sustainable, driving culture.
This paper explores some potential hazards associated with electric vehicles and considers how the risks to users are mitigated by European Union and United Nations type-approval regulations. In doing so, it highlights any gaps in the regulations and the international efforts that are currently underway to close them. Vehicle hazards are the main focus for this work, and some consideration is given to the way they are likely to be used by the public. However, hazards relating specifically to infrastructure, such as vehicle charging or battery exchange are generally not included because they are likely to fall under a different regulatory framework.
The National Highway Traffic Safety Administration (NHTSA) recently updated its 2003 and 2010 logistic regression analyses of the effect of a reduction in light-duty vehicle mass on US societal fatality risk per vehicle mile traveled (VMT; Kahane, 2012). Societal fatality risk includes the risk to both the occupants of the case vehicle as well as any crash partner or pedestrians. The current analysis is the most thorough investigation of this issue to date. This paper replicates the Kahane analysis and extends it by testing the sensitivity of his results to changes in the definition of risk, and the data and control variables used in the regression models. An assessment by Lawrence Berkeley National Laboratory (LBNL) indicates that the estimated effect of mass reduction on risk is smaller than in Kahane's previous studies, and is statistically non-significant for all but the lightest cars (Wenzel, 2012a). The estimated effects of a reduction in mass or footprint (i.e. wheelbase times track width) are small relative to other vehicle, driver, and crash variables used in the regression models. The recent historical correlation between mass and footprint is not so large to prohibit including both variables in the same regression model; excluding footprint from the model, i.e. allowing footprint to decrease with mass, increases the estimated detrimental effect of mass reduction on risk in cars and crossover utility vehicles (CUVs)/minivans, but has virtually no effect on light trucks. Analysis by footprint deciles indicates that risk does not consistently increase with reduced mass for vehicles of similar footprint. Finally, the estimated effects of mass and footprint reduction are sensitive to the measure of exposure used (fatalities per induced exposure crash, rather than per VMT), as well as other changes in the data or control variables used. It appears that the safety penalty from lower mass can be mitigated with careful vehicle design, and that manufacturers can reduce mass as a strategy to increase their vehicles' fuel economy and reduce greenhouse gas emissions without necessarily compromising societal safety.
A new average CO2 emissions limit for passenger cars was introduced in EU in 2009 imposing gradual average CO2 emissions reduction to 130g/km until 2015. This paper attempts to study possible changes in vehicle characteristics for meeting this limit taking into account the average European passenger car of 2007–2008. For this purpose first the most important factors affecting vehicle fuel consumption over the reference cycle (NEDC) are identified. At a second step, the CO2 benefit from the optimisation of these factors is quantified, through simulations of 6 different passenger cars commonly found in the European fleet. For the simulations Advisor 2002 was employed and validated against published type approval data. The analysis indicated that substantial reductions in vehicle weight, tyre rolling resistance and engine efficiency are necessary to reach even the 2008 target. A 10% reduction in average vehicle weight combined with 10% better aerodynamic characteristics, 20% reduced tyre rolling resistance and a 7.5% increase in average powertrain efficiency can lead to CO2 reductions of approximately 13% (about 138g/km based on 2007–2008 fleet-wide performance). Complying with the 130g/km within the next six-year timeframe will be a rather difficult task and additional technical measures appear to be necessary.
The National Highway Traffic Safety Administration (NHTSA) recently updated its 2003 and 2010 logistic regression analyses of the effect of a reduction in light-duty vehicle mass on US fatality risk per vehicle mile traveled (VMT). The current NHTSA analysis is the most thorough investigation of this issue to date. LBNL's assessment of the analysis indicates that the estimated effect of mass reduction on risk is smaller than in the previous studies, and statistically non-significant for all but the lightest cars. The effects three recent trends in vehicle designs and technologies have on societal fatality risk per VMT are estimated, and whether these changes might affect the relationship between vehicle mass and fatality risk in the future. Side airbags are found to reduce fatality risk in cars, but not necessarily light trucks or CUVs/minivans, struck in the side by another light-duty vehicle; reducing the number of fatalities in cars struck in the side is predicted to reduce the estimated detrimental effect of footprint reduction, but increase the detrimental effect of mass reduction, in cars on societal fatality risk. Better alignment of light truck bumpers with those of other vehicles appears to result in a statistically significant reduction in risk imposed on car occupants; however, reducing this type of fatality will likely have little impact on the estimated effect of mass or footprint reduction on risk. Finally, shifting light truck drivers into safer, car-based vehicles, such as sedans, CUVs, and minivans, would result in larger reductions in societal fatalities than expected from even substantial reductions in the masses of light trucks. A strategy of shifting drivers from truck-based to car-based vehicles would reduce fuel use and greenhouse gas emissions, while improving societal safety.
A predictive system for car fuel consumption using a radial basis function (RBF) neural network is proposed in this paper. The proposed work consists of three parts: information acquisition, fuel consumption forecasting algorithm and performance evaluation. Although there are many factors affecting the fuel consumption of a car in a practical drive procedure, in the present system the relevant factors for fuel consumption are simply decided as make of car, engine style, weight of car, vehicle type and transmission system type which are used as input information for the neural network training and fuel consumption forecasting procedure. In fuel consumption forecasting, to verify the effect of the proposed RBF neural network predictive system, an artificial neural network with a back-propagation (BP) neural network is compared with an RBF neural network for car fuel consumption prediction. The prediction results demonstrated the proposed system using the neural network is effective and the performance is satisfactory in terms of fuel consumption prediction.
A predictive system for car fuel consumption using a back-propagation neural network is proposed in this paper. The proposed system is constituted of three parts: information acquisition system, fuel consumption forecasting algorithm and performance evaluation. Although there are many factors which will effect the fuel consumption of a car in a practical drive procedure, however, in the present system the impact factors for fuel consumption are simply decided as make of car, engine style, weight of car, vehicle type and transmission system type which are used as input information for the neural network training and fuel consumption forecasting procedure. In the fuel consumption forecasting, to verify the effect of the proposed predictive system, an artificial neural network with back-propagation neural network has a learning capability for car fuel consumption prediction. The prediction results demonstrated that the proposed system using neural network is effective and the performance is satisfactory in fuel consumption prediction.
A new average CO2 emissions limit for passenger cars was introduced in EU in 2009 imposing gradual average CO2 emissions reduction to 130Â g/km until 2015. This paper attempts to study possible changes in vehicle characteristics for meeting this limit taking into account the average European passenger car of 2007-2008. For this purpose first the most important factors affecting vehicle fuel consumption over the reference cycle (NEDC) are identified. At a second step, the CO2 benefit from the optimisation of these factors is quantified, through simulations of 6 different passenger cars commonly found in the European fleet. For the simulations Advisor 2002 was employed and validated against published type approval data. The analysis indicated that substantial reductions in vehicle weight, tyre rolling resistance and engine efficiency are necessary to reach even the 2008 target. A 10% reduction in average vehicle weight combined with 10% better aerodynamic characteristics, 20% reduced tyre rolling resistance and a 7.5% increase in average powertrain efficiency can lead to CO2 reductions of approximately 13% (about 138Â g/km based on 2007-2008 fleet-wide performance). Complying with the 130Â g/km within the next six-year timeframe will be a rather difficult task and additional technical measures appear to be necessary.
This technical note relates to a paper by Lam (4), “Estimating Fuel Consumption from Engine Size”, which recently appeared in this journal. Using the average travel speed model and data primarily from official fuel consumption tests, Lam investigated the relationship between engine capacity and fuel consumption. However, it is difficult to isolate the effects of individual vehicle characteristics using a very aggregate model such as the average travel speed model. The approach used by Lam could be described as a correlation/regression approach. This type of approach can cause inconsistencies and
anomalies when estimating fuel consumption, and may lead to errors in the interpretation of parameters. To determine the actual effect of any one vehicle characteristic, it is necessary to include all relevant characteristics in the fuel consumption model. Regression estimation of these effects, especially in aggregate models, may not result in reliable estimates due to multicollinearity caused by high correlation between the vehicle parameters.
Since 1975, the fuel economy of passenger cars and light trucks has been regulated by the corporate average fuel economy (CAFE) standards, established during the energy crises of the 1970s. Calls to increase fuel economy are usually met by a fierce debate on the effectiveness of the CAFE standards and their impact on highway safety. A seminal study of the link between CAFE and traffic fatalities was published by R. W. Crandall and J. D. Graham in 1989. They linked higher fuel economy levels to decreases in vehicle weight and correlated the decline in new car weight with about a 20% increase in occupant fatalities. The time series available to them, 1947-1981, includes only the first 4 years of fuel economy regulation, but any statistical relationship estimated over such a short period is questionable. This paper reexamines the relationship between U.S. light-duty vehicle fuel economy and highway fatalities from 1966 to 2002. Cointegration analysis reveals that the stationary lin-
This paper analyzes the impact of changes in average fuel efficiency on traffic-related fatalities while controlling for other confounding effects. These other effects include population, per capita income, per capita alcohol consumption, existence of safety-belt laws (and safety-belt usage), and age cohorts in the population. State-level time-series data over 24 years is used with a fixed effect negative binomial regression model that accounts for both the distributional properties of accident count data and heterogeneity. Other studies of this issue have not used either panel data in this way nor have they used appropriate statistical methods for count data. Results vary with the selection of the time series used. Overall results suggest that while there may have been an association between fleet fuel efficiency improvements and traffic fatalities in the 1970s, this has largely disappeared. There are suggestions that variance in the composition of the vehicle fleet may have adverse safety impacts.
Description
Most of the problems associated with the safety, economy, and overall quality of road transportation are affected by the characteristics of both roads and vehicles and by the manner in which these two dynamic systems interact. Unlike other publications that deal with either vehicles or roads, STP 1225 places equal emphasis on the vehicle and the roadway.
16 peer-reviewed papers written by top researchers in the field cover:
• Modeling and Simulation of Vehicle Dynamics and Vehicle-Road Dynamic Interaction
• Laboratory and Field Tests of Vehicle-Induced Pavement Ladings
• Tire Characteristics
• Ride Quality and Road Roughness
• Advances in Vehicle Suspension Design and Dontrol
• Noise Emission due to Vehicle-Tire-Road Interaction
• and Fuel Efficiency and Rolling Resistance.
Since 1975, the fuel economy of passenger cars and light trucks has been regulated by the corporate average fuel economy (CAFE) standards, established during the energy crises of the 1970s. Calls to increase fuel economy are usually met by a fierce debate on the effectiveness of the CAFE standards and their impact on highway safety. A seminal study of the link between CAFE and traffic fatalities was published by R. W. Crandall and J. D. Graham in 1989. They linked higher fuel economy levels to decreases in vehicle weight and correlated the decline in new car weight with about a 20% increase in occupant fatalities. The time series available to them, 1947–1981, includes only the first 4 years of fuel economy regulation, but any statistical relationship estimated over such a short period is questionable. This paper reexamines the relationship between U.S. light-duty vehicle fuel economy and highway fatalities from 1966 to 2002. Cointegration analysis reveals that the stationary linear relationships between the average fuel economy of passenger cars and light trucks and highway fatalities are negative: higher miles per gallon is significantly correlated with fewer fatalities. Log–log models are not stable and tend to produce statistically insignificant (negative) relationships between fuel economy and traffic fatalities. These results do not definitively establish a negative relationship between light-duty vehicle fuel economy and highway fatalities; instead they demonstrate that national aggregate statistics cannot support the assertion that increased fuel economy has led to increased traffic fatalities.
In the context of the DECADE project, carried out under the 5th Framework Programme of the European Commission, a software package has been developed to predict vehicle fuel consumption and emissions for a given distance–speed profile. In order to give input to the model, specific light duty vehicles have been subjected to intensive measurements on engine dynamometers, on chassis dynamometers, on proving ground and in real traffic. This paper gives an overview of the emissions measured on the road for two vehicles in Belgium and in Spain (in urban, rural and motorway traffic), and compares these with the results obtained on chassis dynamometers. The tests on chassis dynamometers focused mainly on the European Drive Cycle, but a number of tests were performed using a cycle derived from real world speed profiles. When comparing emissions on a grams per kilometer basis, it was established that some of the emissions measured in the certification cycle differed dramatically from the real traffic emissions.
The potential for improving the fuel economy of conventional, gasoline-powered automobiles through optimized application of recent technology advances is analyzed. Results are presented at three levels of technical certainty, ranging from technologies already in use to technologies facing technical constraints (such as emissions control problems) which might inhibit widespread use. A fleet-aggregate, engineering-economic analysis is used to estimate a range of U.S. new car fleet average fuel economy levels achievable given roughly 10 years of lead time. Technology cost estimates are compared to fuel savings in order to determine likely cost-effective levels of fuel economy, which are found to range from 39 miles per gallon to 51 miles per gallon depending on technology certainty level. The corresponding estimated increases in average new car price range from 790 (19930.50 per gallon, indicating that these levels of fuel economy improvement are cost-effective over a vehicle lifetime. A vehicle stock turnover model is used to project the reductions in gasoline consumption and associated emissions that would follow if the estimated fuel economy levels are achieved. Potential trade-offs regarding vehicle performance, safety, and emissions are also discussed.
The Dutch car-fleet specific fuel consumption has not shown any decrease since 1990. The main reasons for the car-fleet specific fuel consumption no longer showing a decrease after 1990, namely, increases in vehicle weight and cylinder capacity, have been concluded from an analysis of Dutch car-fleet specific fuel consumption in the period 1980–1997. The increase in weight of the average sales-weighted new car in this period can be almost completely explained by the increase in weight of successive models (upgrading). This upgrading is partly the result of competition between car manufacturers but is also due to stricter safety requirements. However, because upgrading has been fairly extreme, the 1981 model of a car type often belonged to a different car type than the 1997 model of the same type. Upgrading is therefore a consequence, not only of the competition among car manufacturers and stricter safety requirements, but probably also of the shift in consumer demand for more expensive, larger and heavier cars. The 1998 agreement with the European car manufacturers (ACEA) and the Dutch CO2 differentiation in car purchase taxes will probably lead to a further decrease in specific fuel consumption in the European fuel test-cycle (Eurotest) in the near future. However, real-world specific fuel consumption will decrease less because the difference between specific fuel consumption measured in the Eurotest and real-world specific fuel consumption is expected to increase as a result of the increasing use of both air conditioners and direct-injection gasoline engines.
This paper presents a parametric study of the energy demands of car transportation on two competing inter-city commuter routes in the UK for all main categories of automotive vehicles. The commuter routes are between Bristol and Bath: one is fast and flat, the other is relatively hilly and with tighter speed restrictions. Energy demands were found to be closely related to the vehicle mass because almost all external forces on the car are either directly or indirectly influenced by the mass of the vehicle. Exposure to the wind was found to be an important parameter that can significantly affect fuel consumption. Reducing vehicle mass is an important way of improving the performance of the car. However, there are limits to what can be achieved in weight reduction because of safety requirements and the desire of car owners to have many luxury items in modern cars. The official European fuel consumption and emissions test is limited in the extent to which it measures parameters that affect fuel consumption. For example, the test does not measure the frontal area or drag coefficient of the car. The design of the route and traffic operation can have a very significant influence on the efficiency of car transportation and therefore it is necessary to consider route design in whole-life analysis.
Proposed increases in corporate average fuel economy standards would probably lead to lighter cars. Well-established relationships between occupant risk and car mass predict consequent additional casualties. However, if size, not mass, is the causative factor in these relationships, then decreasing car mass need not increase risk. This study examines whether mass or size is the causative factor.
Data from the Fatal Accident Reporting System are used to explore relationships between car mass, car size (as represented by wheelbase), and driver fatality risk in two-car crashes.
When cars of identical (or similar) wheelbase but different mass crash into each other, driver fatality risk depends strongly on mass; the relationship is quantitatively similar to that found in studies that ignore wheelbase. On the other hand, when cars of similar mass but different wheelbase crash into each other, the data reveal no dependence of driver fatality risk on wheelbase.
Mass is the dominant causative factor in relationships between driver risk and car size in two-car crashes, with size, as such, playing at most a secondary role. Reducing car mass increases occupant risk.
This paper aims at explaining the results of a recent empirical study that found that when cars of unequal mass crash into each other, the ratio of driver fatality risk in the lighter care to risk in the heavier car (the fatality risk ratio) increased as a power function of the ratio of the mass of the heavier car to that of the lighter car (the mass ratio). The present study uses two sources of information to examine the relationship between these same quantities: first, calculations based on Newtonian mechanics, which show that when two cars crash head-on into each other, the ratio of their changes in speed (delta-v) is inversely proportional to mass ratio; second, National Accident Sampling System data, which show how delta-v affects driver injury risk. The study is performed for fatalities and severe injuries and for unbelted and belted drivers. Combining the two sources of information gives the result that fatality risk ratio increases as a power function of mass ratio, the same functional form found in the empirical study. Because the study is rooted in Newtonian mechanics, it clearly and directly identifies physical mechanisms involved and leads to the conclusion that mass, as such, causes large differences in driver injury and fatality risk when cars of unequal mass crash into each other.
The finding that the relative safety disadvantage of small compared with large cars is less for post-1980 cars than for pre-1980 cars has stimulated speculation that increasing fuel economy standards would increase fatalities less than previously expected. Fatal crashes between two cars of similar model year were examined to see whether this would be the case.
Driver fatality risk in relation to car mass was examined with Fatal Accident Reporting System data for crashes between two cars of a specific model year.
The relative risk for driver fatality in the lighter car compared with the other driver's risk in a car 50% heavier was as follows: for 1966 through 1979 cars, the risk was between 3.7 and 5.1; for 1984 cars, 2.6; and for 1990 cars, 4.1.
The results suggest that the lesser mass effect observed for mid-1980s cars occurred because improved crashworthiness features appeared in small cars earlier than in large cars. As all cars are redesigned, the relationship between risk and mass can be expected to approach that observed earlier in pre-1980 cars. If so, future fatality increases from fuel economy increases will be greater than estimated on the basis of mid-1980 data.
The relative risk, R, of a driver fatality in the lighter of two cars compared to the risk in the heavier is determined as a function of the ratio, mu, of the mass of the heavier to that of the lighter, using Fatal Accident Reporting System data for 1975-1989. In all of many cases investigated, the data fitted well the functional relationship R = A mu u. When the cars differ only in mass, A = 1; if they differ in another dichotomous characteristic, such as old compared to new model years, A estimates the influence of this other characteristic when the masses are equal. The results show that if a driver transfers to a car lighter by 1%, that driver's fatality risk in a two-car crash compared to the risk to the other involved driver increases by between 2.7% and 4.3%, the specific value depending on other factors, such as model year. When one car crashes head-on into the side of another of equal mass, driver fatality risk in the side-impacted car compared to that in the frontally impacted car is 4.5 +/- 0.6 times as great for right-side impacts and 10.1 +/- 1.7 times as great for left-side impacts. Extending the analysis to vehicles other than cars provides empirical evidence that two previously stated "laws" apply systematically over a wide spectrum of vehicles, from mopeds, through motorcycles, small cars, large cars, small trucks to large trucks. These laws are that, when other factors are equal, (1) the lighter the vehicle, the less risk to other road users, and (2) the heavier the vehicle, the less risk to its occupants.
The accident records of different models of car can be compared statistically, provided that accident data which allow the make and model of accident-involved cars to be identified are collected on a national scale: this has been done in Great Britain since 1989. This paper considers the theoretical basis for comparing safety and shows that, because of the lack of detailed exposure data, the most which can currently be achieved is to measure the level of secondary safety (also known as crashworthiness). Based on mathematical considerations, it is shown that the best measure of secondary safety of a particular model is the proportion of drivers who are injured when involved in a two-car accident where one or other driver is injured. In order to minimize bias, this proportion should be adjusted statistically to allow for the influence on the accident data of factors such as type of road and age of driver.
This paper describes the second part of a study of the ways in which the accident records of different models of car can be compared on the basis of suitably detailed national accident data. An earlier paper (Broughton 1995) showed, from theoretical considerations, that the most satisfactory safety index is the one currently used by the British Department of Transport (DoT) to measure the level of secondary safety (crashworthiness). This paper presents empirical tests using British accident data from 1989-92 which confirm its value. It also describes a modelling approach which yields the same index and thus provides a theoretical justification for the DoT index. The index declines linearly with mass of model; a second safety index is developed on the basis of this relation which allows models of widely differing masses to be compared directly.
This paper develops earlier research into statistical methods for comparing the secondary safety of car models. Two papers (Broughton 1996a,b, Accident Analysis and Prevention, Vol. 28, pp. 89-99, and pp. 101-109, respectively) had concluded that the most satisfactory index of secondary safety is the one first used in publications of the U.K. Department of Transport, referred to as the British or DoT index. This paper shows that the distribution of the risk of injury when two cars collide depends principally on the difference in mass; as this rises, the driver of the lighter car is more likely to be injured and the driver of the heavier car is less likely to be injured, while the likelihood of both being injured reduces slightly. It also shows that the level of protection in fatal and serious accidents varies between models to a significantly greater extent than the level in all injury accidents. Car models of similar mass can provide significantly different levels of protection to their occupants, so there would be fewer casualties if all models were to provide the same level of protection as the most successful current designs. It is estimated that if the safety of all models were improved to the level achieved or exceeded by the safest twentieth of models then the number of drivers injured in two-car accidents would fall by 12% and the number killed or seriously injured by 22%.
In this paper the passive safety of cars is examined in the context of the influence of car size and mass on the relative safety of cars. The fundamental relationships of Newtonian mechanics are used to derive a generalized equation for the relative safety of cars of different sizes when involved in frontal collisions. Further equations are derived for collisions between cars of similar size and for single vehicle crashes. These are combined with overall injury criteria to give a series of predicted Relative Injury Risk relationships. Theory shows that in collisions between cars of similar size and in single vehicle accidents the fundamental parameter which determines Relative Injury Risk is the size, i.e. the length of the car whereas in collisions between dissimilar sized cars the fundamental parameters are the masses and the structural energy absorption properties of the cars. The predictions from the theoretical models are compared with the results of field evaluations of Relative Injury Risk to car occupants carried out in the U.S.A. and in Europe for car to car and single vehicle collisions. There is a high level of correlation between the theory and the field evaluations of Relative Injury Risk. Finally the overall structural crush behaviour of cars is reviewed and ways of further improving the overall passive safety of cars proposed.
This study estimated how adding mass, in the form of a passenger, to a car crashing head-on into another car affects fatality risks to both drivers. The study distinguished the causal roles of mass and size.
Head-on crashes between 2 cars, one with a right-front passenger and the other with only a driver, were examined with Fatality Analysis Reporting System data.
Adding a passenger to a car led to a 14.5% reduction in driver risk ratio (risk to one driver divided by risk to the other). To divide this effect between the individual drivers, the author developed equations that express each driver's risk as a function of causal contributions from the mass and size of both involved cars. Adding a passenger reduced a driver's frontal crash fatality risk by 7.5% but increased the risk to the other driver by 8.1%.
The presence of a passenger reduces a driver's frontal crash fatality risk but increases the risk to the driver of the other car. The findings are applicable to some single-car crashes, in which the driver risk decrease is not offset by any increase in harm to others. When all cars carry the same additional cargo, total population risk is reduced.
We study the dependence of risk on vehicle type and especially on vehicle model. Here, risk is measured by the number of driver fatalities per year per million vehicles registered. We analyze both the risk to the drivers of each vehicle model and the risk the vehicle model imposes on drivers of other vehicles with which it crashes. The "combined risk" associated with each vehicle model is simply the sum of the risk-to-drivers in all kinds of crashes and the risk-to-drivers-of-other-vehicles in two-vehicle crashes. We find that most car models are as safe to their drivers as most sport utility vehicles (SUVs); the increased risk of a rollover in a SUV roughly balances the higher risk for cars that collide with SUVs and pickup trucks. We find that SUVs and to a greater extent pickup trucks, impose much greater risks than cars on drivers of other vehicles; and these risks increase with increasing pickup size. The higher aggressivity of SUVs and pickups makes their combined risk higher than that of almost all cars. Effects of light truck design on their risk are revealed by the analysis of specific models: new unibody (or "crossover") SUVs appear, in preliminary analysis, to have much lower risks than the most popular truck-based SUVs. Much has been made in the past about the high risk of low-mass cars in certain kinds of collisions. We find there are other plausible explanations for this pattern of risk, which suggests that mass may not be fundamental to safety. While not conclusive, this is potentially important because improvement in fuel economy is a major goal for designers of new vehicles. We find that accounting for the most risky drivers, young males and the elderly, does not change our general results. Similarly, we find with California data that the high risk of rural driving and the high level of rural driving by pickups does not increase the risk-to-drivers of pickups relative to that for cars. However, other more subtle differences in drivers and the driving environment by vehicle type may affect our results.
In the US motor vehicle fuel economy standards were imposed in the late 1970s, in response to the oil crises of that decade. Since then, efforts to increase the standards have not occurred, one reason being the argument that smaller vehicles (which are generally more efficient) are considered less safe. Recent analyses (Energy J.( 2004)) suggests that variance in vehicle weights may be more important than the absolute weights of vehicles in making the highway network less safe. In Europe and other countries, which generally have smaller more efficient vehicle fleets, due to relatively high gasoline taxes, this debate has not occurred. In particular, countries such as Great Britain and Sweden have far safer road transport systems than the US but also have much more efficient vehicle fleets. This suggests that either vehicle weight and size are unimportant or if they have an effect it is small compared to other factors. This paper uses international data to build econometric models that examine whether average vehicle fuel economy has any association with road traffic fatalities, while controlling for other factors that are associated with fatalities. The effect on pedestrian fatalities is also analyzed. Cross-sectional time-series data on traffic fatalities from OECD countries is used and negative binomial regression models are developed using panel data to determine whether any associations are present. Results find that changes in vehicle efficiency are not associated with changes in traffic fatalities, suggesting either that size and weight changes over time have not had a strong effect or are not associated with fuel economy improvements.
Generalized Linear Models Effectiveness and Impact of Corporate Average Fuel Economy (CAFE) Standards
- P Mccullagh
- J A Nelder
McCullagh, P., Nelder, J.A., 1983. Generalized Linear Models. Chapman and Hall, London. National Research Council (NRC), 2002. Effectiveness and Impact of Corporate Average Fuel Economy (CAFE) Standards. National Academy Press, Washington, DC.
On estimating fuel consumption and CO 2 emission rates for any driving cycle. Traffic Demand Management Symposium
- H R Kirby
Kirby, H.R., 2005. On estimating fuel consumption and CO 2 emission rates for any driving cycle. Traffic Demand Management Symposium, 2–4 August 2005, Edinburgh. <http://www.tri.napier.ac.uk/events/TDM/kirbypaper.pdf> (accessed May 2007).
Vehicle mass as a determinant of fuel consumption and safety performance. CTS Working Paper 01-2007, ISSN 1747-6232 Why has car-fleet specific fuel consumption not shown any decrease since 1990? Quantitative analysis of Dutch passenger car-fleet specific fuel consumption
- R R Tolouei
- Van Wee
Tolouei, R., 2007. Vehicle mass as a determinant of fuel consumption and safety performance. CTS Working Paper 01-2007, ISSN 1747-6232, University College London, London. Van den Brink, R., Van Wee, B., 2001. Why has car-fleet specific fuel consumption not shown any decrease since 1990? Quantitative analysis of Dutch passenger car-fleet specific fuel consumption. Transportation Research Part D 6, 75–93.
Cars: make and model: the risk of driver injury in Great Britain
- Department
- Transport
Department of Transport, 2006. Cars: make and model: the risk of driver injury in Great Britain: 2000–2004.
Casualty rates by type of car
- J Broughton
Broughton, J., 2007. Casualty rates by type of car. TRL Report No. PPR 203, TRL Limited, Crowthorne.
European Commission Directive 93/116/EC of 17 December 1993, adapting to technical progress Council Directive 80/1268/ EEC relating to the fuel consumption of motor vehicles
Department of Transport, 2006. Cars: make and model: the risk of driver injury in Great Britain: 2000-2004. Transport Statistics Bulletin, HMSO, London.
European Commission, 1993. European Commission Directive 93/116/EC of 17 December 1993, adapting to technical progress Council Directive 80/1268/
EEC relating to the fuel consumption of motor vehicles. Official Journal of the European Communities, L 329, 39-53.
amending Council Directives 70/156/EEC and 80/1268/EEC as regards the measurement of carbon dioxide emissions and fuel consumption of N1 vehicles
European Commission, 2004. European Commission Directive 2004/3/EC of 11 February 2004, amending Council Directives 70/156/EEC and 80/1268/EEC as
regards the measurement of carbon dioxide emissions and fuel consumption of N1 vehicles. Official Journal of the European Union, L 49, 36-41.
Relationships between vehicle size and fatality risk in model year 1985-1993 passenger cars and light trucks
- C J Kahane
Kahane, C.J., 1997. Relationships between vehicle size and fatality risk in model year 1985-1993 passenger cars and light trucks. NHTSA DOT HS 808 570, US
Department of Transportation, National Highway Traffic Safety Administration, Washington, DC.
On estimating fuel consumption and CO2 emission rates for any driving cycle
- H R Kirby
Kirby, H.R., 2005. On estimating fuel consumption and CO 2 emission rates for any driving cycle. Traffic Demand Management Symposium, 2-4 August 2005,
Edinburgh. <http://www.tri.napier.ac.uk/events/TDM/kirbypaper.pdf> (accessed May 2007).
Effectiveness and Impact of Corporate Average Fuel Economy (CAFE) Standards
- P Mccullagh
- J A Nelder
McCullagh, P., Nelder, J.A., 1983. Generalized Linear Models. Chapman and Hall, London.
National Research Council (NRC), 2002. Effectiveness and Impact of Corporate Average Fuel Economy (CAFE) Standards. National Academy Press,
Washington, DC.
Vehicle mass as a determinant of fuel consumption and safety performance
- R Tolouei