bluuebunny/crossref_metadata_2025 huggingface dataset:
Outcome-Oriented Performance Measures for Management of Signalized Arterial Capacity
Authors: Day Christopher M. , Sturdevant James R. , Bullock Darcy M.
Published: February 2011

The design of traffic signal timing plans is typically based on a single day of manual turning movement counts. Once systems are constructed and settings are implemented, they receive maintenance on fixed schedules of a number of years. Public feedback (e.g., phone calls) is in many cases the primary channel by which an agency obtains feedback about the system. System assessment is often conducted by collecting a new small data sample and repeating the design process. One common and frustrating result is that the same settings are frequently recommended by the design software even when problems are known to exist. This paper illustrates how fundamental traffic engineering concepts can be integrated with traffic signal system detection and controller status information to provide outcome-based measures of arterial-system performance. These outcome-based measures of performance characterize the operation of a signal system and provide a data set that can be used to identify and prioritize opportunities for operational improvements in the system. A consistent set of performance measures used across a signal network would affect traffic signal operations at two distinct levels. At the regional or district level, it would provide a continuously updated list of problem areas with greater accuracy than telephone reports. At the agency jurisdiction level, it would provide quantitative data for prioritizing resources across multiple districts and by time of day.
Evaluation of Arterial Signal Coordination
Authors: Day Christopher M. , Haseman Ross , Premachandra Hiromal , Brennan Thomas M. , Wasson Jason S. , Sturdevant James R. , Bullock Darcy M.
Published: February 2011

Signal offsets are a signal-timing parameter that has a substantial impact on arterial travel times. The traditional technique is to optimize offsets with an offline software package, implement the settings, and then possibly observe field operations. It is not uncommon for a traffic engineer to fine-tune the settings by observing the arrivals of platoons at an intersection and making adjustments to the offset from this qualitative visual analysis. This paper discusses two tools to assist the engineer in managing arterial offsets. First, it introduces the Purdue coordination diagram (PCD) as a means of visualizing a large amount of controller and detector event data to allow investigation of the time-varying arrival patterns of coordinated movements. The second technique is arterial travel time measurement by vehicle reidentification via address matching by Bluetooth media access control. This technique is used to evaluate existing offsets and assess the impact of implemented offset changes. These tools are demonstrated with a case study involving a before-and-after comparison of an offsettuning project. PCDs were used to identify causes of poor progression in the before case, as well as to visualize both the predicted and the actual arrival patterns associated with the optimized offsets. More than 300 travel time measurements from Bluetooth probes were used for statistical assessment of before-and-after travel time. The statistical comparison showed a significant (at the 99% level) 1.7-min reduction (28%) in mean northbound travel time, corresponding to a 1.9-min reduction in median northbound travel time. Southbound travel times were not negatively affected by the offset changes.
Crosstalk Detection in Signalized-Intersection Loop Detectors
Authors: Ernst Joseph M. , Lamba Dhruv , Krogmeier James V. , Bullock Darcy M.
Published: February 2011

Electromagnetic sensors, such as inductive loops and microloops, are widely used for vehicle detection. However, electrical coupling can occur between detection devices and result in electrical noise called crosstalk, which significantly degrades detection operation. Techniques such as channel scanning and frequency separation have been used to mitigate crosstalk; however, crosstalk is often transient because of environmental conditions and not always observed easily. This paper presents a crosstalk detection algorithm based on 156 h of training data taken from 12 sensors (inductive and microloop) and applies it to approximately 14 h of data collected from seven sensors (four inductive loops and three microloops) to demonstrate an automated method to identify periods when crosstalk occurs. The paper concludes by recommending the use of this approach for system acceptance and ongoing monitoring of sensor health.
Signal Priority near Major Bus Terminal
Authors: Furth Peter G. , Cesme Burak , Rima Tarannum
Published: February 2011

Near major bus terminals, multiple bus arrivals per signal cycle and a convergence of buses from conflicting directions can make it impractical to apply signal priority logic that attempts to interrupt the signal cycle for each bus. This research explores signal control logic for reducing bus delay around a major bus terminal in Boston, Massachusetts, where the busiest intersections see almost four buses per signal cycle. With a traffic microsimulation to model a succession of signal priority tactics, a reduction in bus delay of 22 s per intersection was obtained, with no significant impact on general traffic. The general strategy was to provide buses with green waves, so that they are stopped at most once, coupled with strategies to minimize initial delay. The greatest delay reduction came from passive priority treatments: changing phase sequence, splits, and offsets to favor bus movements. Green extension and green insertion were found to be effective for reducing initial delay and for providing dynamic coordination. Dynamic phase rotation, from lagging to leading left, proved less effective. Cycle-constrained free actuation, in which an intersection has a fixed cycle length within which two phases can alternate freely, provided flexibility for effective application of early green and green extension at one intersection with excess capacity. Emphasis is given to the approach of providing aggressive priority with compensation for interrupted phases, highlighting the compensation mechanism afforded by actuated control with snappy settings and long maximum greens.
Traffic Signal Transition in Coordinated Meshed Networks
Authors: Pohlmann Tobias , Friedrich Bernhard
Published: February 2011

Transition of signal plans in networks with controlled traffic lights always has a disruptive impact on traffic flow. The extent of these disruptions depends on the transition method, and therefore increases in delay or travel time may be more or less severe. The task of transitioning becomes even more complex in coordinated networks in which new coordination patterns have to be established quickly without inducing major disturbances. Several transition methods exist, some of which are rather abrupt; others are smoother. Many of these methods have been analyzed in simulation studies. Two extensive studies investigated not only transition effects at isolated intersections but also transition effects on coordinated arterials. This paper adds to these studies by investigating transition effects in a meshed network with different coordinated relations. Furthermore, an additional transition method and variations of previously tested methods have been considered. Four scenarios have been set up and simulated. The results of this study are discussed in detail, delivering not only information on the overall performance of each method but also allowing for some further insights into what is happening during transition. Some effects at intersections are induced by transition at that very intersection, while others have to be ascribed to neighboring intersections. Dwell methods are unfavorable for undisturbed transitioning; smooth methods perform better, especially if transition takes no more than three cycles. The results of this study are valuable for both time-of-day signal plan selection and for adaptive traffic control strategies.
Generating More Equitable Traffic Signal Timing Plans
Authors: Kesur Khewal Bhupendra
Published: February 2011

Signal timing plans designed under a total delay minimization strategy can induce excessively high delays for low-volume movements and result in an uneven distribution of delay among motorists. A multiobjective optimization approach is considered for the minimization of both overall delay and delay imbalance. The multiobjective method is found to be highly successful. Compared with a pure delay minimization strategy, the multiobjective optimizer is able to produce signal timing plans with similar overall delay that have a considerably more equitable delay distribution. Multi-objective optimization provides the traffic engineer with a choice from an entire range of compromise solutions in the two competing objectives. Large reductions in the delay imbalance can be achieved at the cost of small sacrifices in overall delay. Multiphase signal control, shifting green splits in favor of low-volume movements, and decreasing bandwidth provide more-balanced delays at the cost of increasing overall delay.
Uncertainty and Predictability of Urban Link Travel Time
Authors: Zheng Fangfang , Van Zuylen Henk
Published: February 2011

Travel times that vehicles experience in urban road networks are intrinsically uncertain because of the stochastic character of delays at signalized intersections. The ability to capture delay characteristics at signalized intersections is critical for estimating and predicting travel times on urban links. Much research has been done to predict travel time on urban links on the basis of traffic state information (e.g., volumes or speeds). However, the results have not been promising. One important reason is that delays experienced by vehicles on urban links are uncertain because of both traffic conditions and traffic control at intersections. This paper addresses the causes of travel time uncertainty. A probabilistic delay distribution model with stochastic arrivals and departures is proposed to investigate delay uncertainty in both undersaturated and oversaturated conditions. The delay distributions with the Poisson arrival process and with the binomial arrival process are compared. Results show that different arrival patterns have little influence on the delay distribution in undersaturated conditions, although they have significant influence on the delay distribution in oversaturated conditions. The delay distributions under different degrees of saturation are overlapping, which indicates that it is difficult to determine the traffic state for a given single-valued delay and vice versa. The “width” of the delay distribution based on percentiles is used to quantify the delay uncertainty at signalized intersections. The dynamics of delay uncertainty and of delay uncertainty under different degrees of saturation are investigated.
Robust Signal Timing for Arterials under Day-to-Day Demand Variations
Authors: Zhang Lihui , Yin Yafeng , Lou Yingyan
Published: February 2011

This paper formulates a scenario-based stochastic programming model to optimize the timing of pretimed signals along arterials under day-to-day demand variations or future uncertain traffic growth. Demand scenarios and their corresponding probabilities of occurrence are introduced to represent the demand uncertainty. On the basis of a cell-transmission representation of traffic dynamics, cycle length, green splits, phase sequences, and offsets are determined to minimize the expected delay incurred by high-consequence demand scenarios. A simulation-based genetic algorithm is proposed to solve the model, and a numerical example is presented to verify and validate the model.
Hardware-in-the-Loop Simulation Evaluation of Adaptive Signal Control
Authors: Hunter Michael P. , Roe Matthew , Wu Seung Kook
Published: February 2011

Increasingly, adaptive signal control and other nontraditional solutions are being implemented in an attempt to improve signal system efficiencies, reduce congestion, enhance signal control responsiveness to incidents, and reduce signal-retiming costs. However, neither field nor simulation studies alone have proven sufficient to evaluate such systems. To overcome the limitations of field data or simulation-only studies, hardware-in-the-loop simulation (HILS) or software-in-the-loop simulation (SILS) may be used. HILS and SILS provide a means for realistic testing, under controlled and repeatable conditions, of signal strategies not directly emulated in a simulation model. This paper presents the initial findings of a HILS evaluation of ACTRA [i.e., semiactuated, coordinated, time-of-day (TOD)] and adaptive signal control on an 11-intersection arterial section. The HILS test bed generally provides a reasonable representation of both TOD and adaptive signal control performance. However, the adaptive a.m. HILS results contain some unexpected behaviors not observed in the field. The initial findings of the signal control comparison indicate that during peak conditions both control strategies provide similar performance; however, during the hours bordering the peaks, adaptive control is likely able to provide control more tailored to the current conditions.
Analytical Models for Protected plus Permitted Left-Turn Capacity at Signalized Intersection with Heavy Traffic
Authors: Yin Kai , Zhang Yunlong , Wang Bruce X.
Published: February 2011

This paper presents theoretical analysis of left-turn operations under heavy traffic. When traffic demand is heavy, residual queues from previous cycles may occur and contribute to blockage of the left-turn bay by adjacent through traffic. Such blockage reduces the left-turn capacity and is a random phenomenon. An improved model for protected left-turn capacity is first proposed, taking into account the influence of residual queues and blockage by through traffic. In addition, the classic model always overestimates the potential permitted left-turn capacity when opposing traffic is heavy. The potential permitted left-turn capacity is then modeled in a probabilistic way, and a simple estimation is suggested by investigating its relation to the classic model. Furthermore, because left-turn capacity may vary in response to a blockage, the coefficients of variance for protected left-turn capacity and for queue clearance time are introduced to evaluate the protected left-turn timing plan. The developed analytical models are validated with CORSIM simulations.
Africa's First Bus Rapid Transit System
Authors: Kaenzig Robin , Mobereola Dayo , Brader Colin
Published: February 2011

Africa's first bus rapid transit (BRT) scheme became operational in March 2008 in Lagos, Nigeria. Termed “BRT-Lite,” this new form of BRT focuses on the delivery of improved quality of life within a modest budget. The implementation program, from conception to operation, was collapsed into a 15-month time frame; that together with its delivery cost of $1.7m/km made its development unique and its experience relevant to cities throughout the world seeking to develop BRT. BRT-Lite's success cannot be explained by its infrastructure; it is also the result of a holistic approach. That approach involved reorganization of the bus industry, the financing of new buses, the creation of a new institutional structure and regulatory framework of support, and the training of personnel to drive, maintain, enforce, and manage the BRT. While these challenges were being met, the public was engaged and informed about a transportation system of which it had no previous knowledge. Public reception of the concept was immediate and positive. An assessment of BRT-Lite, which followed its inception, found the scheme to be an unprecedented success. The critical success factors were defined as significant and consistent political commitment, the presence and capabilities of a strategic public transport authority, a scheme definition that concentrated on essential user needs and deliverability within a budget and program, engagement of key stakeholders, assurances that the benefits would be widespread, and a community engagement program to ensure that BRT-Lite was seen as a community project created, owned, and used by Lagosians. The future challenge is to meet high demand through rollout of the BRT network.
Carbon Dioxide Reduction Benefits of Bus Rapid Transit Systems
Authors: Hook Walter , Kost Chris , Navarro Ulises , Replogle Michael , Baranda Bernardo
Published: February 2011

Appraisal of the greenhouse gas (GHG) impacts of transportation system interventions, such as investments in bus rapid transit (BRT), is of growing interest to transportation and environmental officials, investors, and other stakeholders. The lack of an accepted methodology to estimate the carbon dioxide (CO2) mitigation potential from modal shift and reductions in vehicle kilometers traveled has inhibited access to GHG-related funding mechanisms. This paper focuses only on development of a common methodology for BRT projects with sufficient information to conduct analysis. Adjustment factors were postulated that might be used to estimate generalized BRT investment impacts in large, developing cities. Parameters were established on the basis of in-depth analyses of the CO2 impacts on three BRT systems: those in Bogotá, Colombia; Mexico City, Mexico; and Jakarta, Indonesia. An analysis of CO2 emission reductions related to the Bogotá BRT system secured Clean Development Mechanism certification for carbon financing in 2006 and followed a corridor-focused methodology. In 2007 to 2008, a regional, integrated transportation–land use model was applied to BRT scenarios for Mexico City. Calculations have been updated on the basis of data from postimplementation passenger surveys. The methodology does not capture some potential sources of emissions savings, such as fuel consumption internal to the bus system. But even accounting for these differences, the Jakarta BRT system could produce much smaller GHG benefits. This paper reports on a preliminary effort to develop a reasonable methodology to estimate CO2 abatement potential at the project level in a way that facilitates aggregation at the national and regional levels.
Bus Rapid Transit in Curitiba, Brazil
Authors: Lindau Luis Antonio , Hidalgo Dario , Facchini Daniela
Published: February 2011

Curitiba, the world's cradle for bus rapid transit (BRT), is an affluent city in Brazil. Its integrated transit network (RIT) is one of the most successful bus transit systems in the Western Hemisphere. RIT is the result of 35 years of continuous upgrades to bus service, which ultimately led to the creation of the BRT concept and lent structure to Curitiba's urban development. The recently inaugurated Green Line (Linha Verde) is the backbone of a renewed urban structural concept, with a linear park and the redevelopment of low-density, industrial properties. The line takes full advantage of evolved BRT concepts, such as cleaner vehicles and fuels and the introduction of passing lanes at stations to increase capacity and improve commercial speeds. The success of Curitiba derives from a mix of political leadership, innovation, pragmatism, technocracy, and continuity. This paper presents Curitiba's main transit milestones over time, barriers to planning and implementation, and measures adopted to solve or mitigate them. A series of recommendations includes (a) improvements in the delivery of quality of service to transit users, (b) conduct of a home-based origin–destination survey to identify the mobility pattern within the metropolitan area, and (c) consideration of value capture mechanisms and public–private partnerships in transit projects.
Cycling Trends and Fate in the Face of Bus Rapid Transit
Authors: Montgomery Brittany Nikole
Published: February 2011

In many Chinese cities, bus rapid transit (BRT) has been promoted as the answer to urban transport needs and, as such, would supplant cycling as a significant mode of transportation. Expectations of the effects of new BRT systems indicate that cycling trips will be absorbed into these new public transit systems. These assumptions about future travel behavior are investigated in the context of Jinan, the capital of Shandong Province, China. A large sample origin–destination survey of traditional and electric bicycles was completed to serve as the basis for comparison with current bus trips and projected travel by BRT. Quantitative methods were used to analyze trip characteristics across modes and the potential travel benefits of BRT. Results from an extensive, qualitative survey of cyclists complement these data, and the survey considered the perceptions of cycling and key reasons for mode choice. Evidence from a comparison of the modal characteristics of traditional cycles, electric bicycles, bus services, and BRT indicates that cycling provides a highly attractive, already existing alternative to public transport. This challenges the assumptions of a substantial modal shift after the implementation of BRT systems and begs for an alternative approach to urban transport system design—one that integrates China's cycling culture. Recommendations on the basis of these findings explore the possibilities for the systematic integration of cycling and BRT.
Evaluation of Pedestrian Safety at Midblock Crossings, Porto Alegre, Brazil
Authors: Diogenes Mara Chagas , Lindau Luis Antonio
Published: February 2011

This paper proposes a method to evaluate the potential risk of pedestrian crashes at midblock crossings, which can be applied in developing countries. The method is quantitative because it uses modeling techniques to represent the relationship of risk factors with the occurrence of pedestrian crashes. Application of the method described here comprised the analysis of reported pedestrian crashes in the city of Porto Alegre, in southern Brazil, between 1998 and 2006, and the identification of midblock crossings with the highest number of pedestrian crashes. Twenty-one midblock crosswalks were selected for evaluation. A Poisson regression model was developed to relate pedestrian crashes to the prevailing operational and physical characteristics of midblock crossings. The results indicate that pedestrian crash risk is influenced by a combination of interactive risk factors, such as the presence of busways and bus stops, the road width, the number of traffic lanes, and the volume of pedestrians and vehicles.
Exploration of Pedestrian Refuge Effect on Safety Crossing at Signalized Intersection
Authors: Li Lingjie , Yang Xiaokuan , Yin Li
Published: February 2011

Pedestrian safety has become a major issue in the traffic management systems of major cities in China. This is particularly true where a signalized intersection is relatively large and a significant number of pedestrians must wait to cross. This study investigated the safety issues of pedestrian crossings at signalized intersections in Beijing. Field observations were conducted and evaluated, and a questionnaire survey was administered to both pedestrians and motorists at 45 signalized intersections in Beijing. Safety implications of pedestrian crossings at wider signalized intersections and traffic conflict analyses are elaborated on with respect to the survey. It can be concluded from this study that it is vital to install a pedestrian refuge island at the medians of roadways to provide pedestrians with a risk-free waiting area to complete two-step crossings. This measure is particularly necessary at signalized intersections where green time designated for pedestrian crossing is scarce. This study shows that a refuge island has proved acceptable to both pedestrians and drivers.
Comprehensive Performance Evaluation Framework for Urban Transport Policies
Authors: Chen Ya-Wen , Chiang Yu-Sheng , Wei Chien-Hung
Published: February 2011

This study describes a framework that is used to analyze urban transport policies in Kaohsiung, the second largest city in Taiwan. The framework is comprehensive in the sense that the full range of transport-related policy elements—investment, pricing, regulation, and subsidies—are explicitly integrated to generate policy alternatives for evaluation. In contrast, past planning processes have tended to focus solely on infrastructure investment. The relationships among these four policy elements were examined in the case study. The results show that an integrated, goal-related transport policy with the four elements is more effective than the traditional, single-element policy. The proposed policy evaluation framework can be implemented in the commonly used urban transportation planning process.
Spatial and Social Characteristics of Urban Transportation in Beijing
Authors: Yang Jiawen
Published: February 2011

This paper aims to improve knowledge of urban transportation in China by analyzing the spatial characteristics of urban transportation in Beijing, China's capital. Neighborhood-level indicators—such as automobile ownership per household, commuting time, commuting mode percentages, and household income—were all extracted from a household survey conducted in 2006. Urban transportation was then analyzed spatially with a reference to Beijing's geometric center, job centers, and urban rail stations. The analysis led to several findings. First, the variation in commuting time by gender and household composition was similar to what has been observed in American cities. Second, automobile ownership and commuting modes exhibited no systematic, spatial variation, unlike their American counterparts. These differences might be explained by a third finding: in China, relatively high-income households preferred centrally located housing.
Motorization in China
Authors: Ni Meng-Cheng , Kurani Kenneth S. , Sperling Daniel
Published: February 2011

Motorization, the substitution of automobiles and trucks for nonmotorized travel modes, has been examined at national and regional levels. Previous studies indicate that, at the national level, income (gross domestic product per capita) typically explains more than 90% of the variation in vehicle ownership. In terms of travel mode transition, some studies have explained part of this phenomenon, but a comprehensive review has rarely been conducted. In this paper, motorization is examined as an individual and as a household phenomenon. At the personal level, motorization occurs through a series of transitions, stereotypically from nonmotorized to motorized, from shared to privately owned, and from low to high cost. Results of a survey of residents of Shanghai, China, in mid-2006 illustrate these personal transitions, or motorization pathways. On the basis of the survey, motorization pathways in Shanghai were found to be diverse (331 distinct pathways across 992 respondents) and complicated (the pathways of more than 50% of respondents involved more than three stages). Only about half of the respondents came to their current motorization stage through a hypothesized motorization direction. This paper indicates that no common path exists toward private automobile ownership in Shanghai. At least at present, Shanghai residents appear to make a transition away from motorized, expensive, private modes of mobility nearly as often as they transition toward them. This implies not only that widespread use of private cars is not inevitable, but that there are many stages along the motorization pathway where government policies could affect mobility choice and guide Shanghai to a more sustainable future.
Modeling Private Car Ownership in China
Authors: Li Jieping , Walker Joan L. , Srinivasan Sumeeta , Anderson William P.
Published: February 2011

The rising prevalence of private cars in the developing world is causing serious congestion and pollution. In China, private cars started to emerge as an important travel mode in the past decade. Prospective research on the relationship between urban form and car ownership is relatively uncommon in the developing world, and China offers a unique study opportunity, given the tremendous increases in private cars and fast-paced urbanization over the past decade. This study investigates the influence of urban form on car ownership as well as the impact of other socioeconomic and demographic factors on private car ownership across megacities in China. Analysis was conducted through the use of data from 36 megacities and two household survey data sets collected in Beijing and the city of Chengdu, China. Ordinary least squares regression and discrete choice models were employed to execute the aggregate and disaggregate analysis of the urban form impact on private car ownership across cities. The statistical model results demonstrate that urban affluence, urban scale, and road infrastructure supply factors have significant positive effects on the city level of private car ownership across cities. Population density calculated at the subdistrict level, however, had a significant negative effect on private car ownership across cities. Households with private cars were found to prefer to live close to urban centers where amenities were readily available. The results provide evidence for urban planners and policy makers.
Linking Travel Behavior and Location in Chengdu, China
Authors: Srinivasan Sumeeta
Published: February 2011

This study uses geographically weighted regressions and multilevel models to understand the implications of location and attitudinal characteristics for travel behavior in Chengdu, China. In particular, the estimated distance traveled and the mode choice of nonmotorized versus motorized vehicles for work- and school-related trips were examined by using a recent household trip diary data set. The results suggest that location characteristics may be influential in the prediction of travel behavior but cannot be fully captured by simple categorization such as inner ring location versus peripheral location. Variations in travel behavior can be related to socioeconomic and location variables in ways that vary by location in a complex manner. Policy makers should therefore reconsider the role that location and attitudinal implications may play in meeting travel demand in rapidly developing cities like Chengdu.
Effects of Personal Factors on Bicycle Commuting in Developing Countries
Authors: Yang Chen , Wang Wei , Shan Xiaofeng , Jin Jing , Lu Jian , Li Zhibin
Published: February 2011

This paper focuses on an analysis of personal factors that affected people's decisions to bicycle for commuting trips. Factors investigated included commuter demographic characteristics, perceived benefits, and trip distance. With samples collected in a commuter survey in Nanjing, China, the odds ratio statistics were developed to analyze the effect of each factor separately. Two latent variables that implied commuter socioeconomic status and perceived benefits were obtained by the factor analysis method. On the basis of the results of the factor analysis, a binomial logit model with the latent variable enriched was developed to describe how the factors influenced commuter choices. For comparison purposes, a binomial logit model without a latent variable was also developed. Both models offered some important insights into the effects of personal factors on bicycle commuting. The findings were (a) trip distance and perceived benefits had significant effects on bicycle usage; (b) socioeconomic status was negatively correlated with bicycle commuting; (c) gender and age had no significant effects on bicycle commuting; (d) commuters cared more about rapidity and convenience than safety and comfort; and (e) automobile availability for a trip was negatively correlated with bicycle commuting. These results have some policy implications for urban transportation planning.
Safety Analysis of Urban Arterials under Mixed-Traffic Patterns in Beijing
Authors: Ma Ming , Yan Xinping , Abdel-Aty Mohamed , Huang Helai , Wang Xuesong
Published: February 2011

Many studies have dealt with modeling crash occurrences on urban arterials. There is a dearth of research on urban arterials with mixed-traffic patterns in China, however, because of the large traffic flow volume of bicyclists and pedestrians in most Chinese cities. This study investigates the risk factors associated with severe crash occurrences on arterial roads in Beijing. Through use of the generalized estimating equations modeling technique with a negative binomial link function, statistical relationships were established to relate severe crashes to a variety of factors related to geometric design, traffic control, and other traffic-related characteristics. Crash records from 2004 to 2007 for 108 signalized intersections and 123.5 km of road segments were used to estimate the models. Results showed that arterial roads with heavier traffic volumes, more road lanes, and higher speed limits tended to have more severe crashes. Medians were helpful in reducing severe crash risk. Higher risks of severe crashes were generally associated with intersections having small angles and countdown signals and road segments having higher side-access densities and the presence of bus stops. With regard to nonmotorist protection facilities, results revealed that a combined use of crosswalks and overpasses was the most desired pedestrian-crossing facility for safety, especially at sites with heavy traffic or sites located in primarily residential areas. Barriers that separated bikeways from roadways on minor roads were found effective in significantly reducing severe crash risk at intersections.
Scenarios for Future Urbanization
Authors: Rayle Lisa , Pai Madhav
Published: February 2011

The growth of motorization and travel activity associated with India's rapid urban development has serious implications for global climate change. Effective mitigation action requires comprehension of the scale of the problem. Data limitations, however, have thus far constrained efforts to understand how changes in demographics, travel behavior, and policy might affect future emissions of greenhouse gases. This study uses recently available data on city-level travel patterns to forecast emissions from passenger transport for three metropolitan areas in India: Mumbai, Ahmedabad, and Surat. The forecasts compare carbon dioxide (CO2) emissions for three scenarios by using various mode choice and trip length assumptions. The results predict dramatic increases in emissions under all circumstances. Travel in Surat is forecast to generate between 1.9 and 9.5 million tons of CO2; in Mumbai, travel could generate 10.3 to 49 million tons. Differences, however, between scenarios suggest the potential positive effects of policy interventions. While the results help convey the magnitude of the emissions problem, further analysis requires more complete data on individual travel behavior.
Literacy, Access, and Mobility
Authors: Dalal Pamela , Goulias Konstadinos G.
Published: February 2011

This study uses data from Sylhet, Bangladesh, to examine the relationship between the distance to school locations and attendance to understand how transport can positively influence school attendance. Logit regression models and a database of 3,402 households were used to correlate household schooling decisions with the built environment, local infrastructure, and household and individual characteristics. Travel demand for school trips was examined to identify how transportation can aid or hinder literacy objectives. Among other findings, two underserved populations were identified: (a) inner-city slum residents and (b) low-income remote households. Two possible transport actions for them are to increase (a) school supply in remote areas to improve accessibility and (b) public investment in affordable bus transit to improve mobility for students who travel to distant school locations. Thus, a combination of economic and transportation policies would likely increase literacy rates and overall educational attainment, which in turn would result in greater future educational equity among Sylhet residents.
Hours of Service and Truck Crash Risk
Authors: Park Sang-Woo , Jovanis Paul P.
Published: February 2011

A case-control study of 231 truck crashes (and 462 controls) was completed with data from three trucking companies from 2004, when new hours-of-service (HOS) regulations went into effect in the United States. Analysis using time-dependent logistic regression indicates that increased crash risk is associated with hours of driving, with risk increases of 50% to 260% compared with the first hour of driving. These findings help to provide a baseline estimate of crash risk relationships for this HOS policy. A series of models indicates that the pattern of crash risk is different for nonsleeper operations and for sleeper schedules. Models of nonsleeper operations indicate that crash risk is strongly associated with multiday driving somewhat more than with hours of driving. Models of sleeper operations indicate strong association of crash risk with hours driving. These findings, though consistent with many results from similar modeling conducted with 1980s data, are subject to important limitations. The small sample size in many cases likely contributed to the relatively high estimates of crash odds (e.g., often in the range of 100% to 200% increases) and to an inability to identify clear trends in some variables. Ideally, this study should be repeated with additional firms over a longer time period. In particular, collecting driver data that cover at least 2 weeks of driving should allow for a much better understanding of the effect of any restart policy. The effects of extended driving, however, strongly suggest that a change back to the 10-h maximum should be considered in any future HOS adjustments.
Condition of Trucks and Truck Crash Involvement
Authors: Blower Daniel , Green Paul E. , Matteson Anne
Published: February 2011

This study, using the Large Truck Crash Causation Study (LTCCS), examined the relationship between the mechanical condition of heavy trucks and crash involvement. Two specific hypotheses were tested. First, trucks with defects and out-of-service (OOS) conditions were statistically more likely to be in the role of precipitating a crash than trucks with no defects or OOS conditions. Second, defects in specific systems, such as the brake system, were associated with crash roles in which those systems were primary mechanisms for avoiding the crash and physical mechanisms that link the vehicle defect with the crash role. Postcrash inspections showed that the condition of the trucks in the LTCCS was poor. Almost 55% of the vehicles had one or more mechanical violations. Almost 30% had at least one OOS condition. Of mechanical systems, violations in the brake system (36% of all) and the lighting system (19%) were the most frequent. Both driver and vehicle factors were found to contribute to crashes. A brake OOS condition increased the odds of the truck's being assigned the critical reason (a variable identifying the precipitating vehicle) by 1.8 times. Both hours of service violations and log OOS violations increased the odds by a larger amount—2.0 and 2.2 times respectively. In rear-end and cross-paths crashes, brake violations, especially violations related to adjustment, increased the odds of the truck's being the striking vehicle by 1.8 times.
Evaluation of Noise Level, Whole-Body Vibration, and Air Quality inside Cabs of Heavy-Duty Diesel Vehicles
Authors: Fu Joshua S. , Calcagno James A. , Davis Wayne T. , Alvarez Albert
Published: February 2011

Heavy-duty diesel vehicles were measured for noise level, whole-body vibration from the driver's seat, and in-cab air quality while the vehicles were parked with engine idling at a rest area and while they were driven. These baseline data will help similar studies determine whether new truck designs have changed these conditions for drivers. Twenty-seven trucks (model years 2006 to 2008) from four manufacturers were tested. Results showed slightly higher noise levels driving on the Interstate versus driving on the state highway. However, overall in-cab noise levels were found to be lower than occupational exposure standards. Evaluation of seating vibration used ISO guidelines. Average vibrations in the x-, y-, and z-axes of the seats were generally found to be well below European Union standard exposures for an 8-h driving day. Inferior road pavement conditions were thought to have contributed to higher vibrations in a few trucks where several instances of the vibrations exceeded the standards. For most trucks, the likely comfort reaction from the vibration magnitude of the driver's seat was “a little uncomfortable.” Air quality was determined by measuring in-cab concentrations of carbon monoxide (CO), oxides of nitrogen (NOX), and particulate matter with less than 2.5 microns aerodynamic diameter (PM2.5). Results indicated a tendency of trucks to self-pollute the cabs during periods of extended parked idling. Although overall CO and NOX concentrations were well below occupational exposure levels, PM2.5 concentrations during several parked-idling scenarios were higher than U.S. Environmental Protection Agency limits for ambient monitoring standards. During driving on public roadways, in-cab concentrations were lower than those measured during the extended parked-idling conditions.
Type of Motor Carrier and Driver History in Fatal Bus Crashes
Authors: Blower Daniel , Green Paul E.
Published: February 2011

The Buses Involved in Fatal Accidents (BIFA) project collects detailed information about buses involved in fatal crashes. The BIFA project is supported by the Federal Motor Carrier Safety Administration. Using BIFA data for 1999 to 2005, this study focuses on factors associated with driver errors in fatal bus crashes involving different bus operator types. Five different carrier types were identified: school, transit, intercity, charter or tour, and other. Many factors were associated with driver error, including bus operation type, age, sex, hours driving, trip type, method of compensation, and previous driving record. A logistic regression model was used to model the probability of driver error. Bus operation type, previous violations, and previous crashes were significant parameters in the model. Prior driver violations and crashes both increased the probability that a driver would have been coded with an error in the crash. Transit and school bus drivers were the least likely to have contributed to the crash. Intercity operations were associated with an increase in the odds by 1.9 times, with a 95% confidence interval from 1.1 to 3.2 times. Charter and other bus operations were associated with significantly higher odds of driver error. The odds ratio for charter or tour bus operations was 1.7 (range of 1.2 to 2.4), and for other buses it was 2.6 (range of 1.9 to 3.6). The other factors were not significant.
Evaluation of Safety Benefits from a Heavy-Vehicle Forward Collision Warning System
Authors: Rakha Hesham A. , Fitch Gregory M. , Arafeh Mazen , Blanco Myra , Hanowski Richard J.
Published: February 2011

Forward collision warning (FCW) systems are designed to alert drivers to an impending rear-end (RE) crash, to allow drivers to respond to a crash threat sooner, and thus to reduce their impact speed or allow them to avoid a crash altogether. This study estimates the safety benefits that may be attained by deploying an FCW system across the national fleet of heavy vehicles. The approach involved identifying RE conflicts within a heavy-vehicle naturalistic driving data set with the use of algorithms that identified potential RE events and removed nonthreatening events. Since the heavy vehicles in this data set were not equipped with FCW systems, the FCW auditory alarm severity and timing were introduced into the data with existing FCW system algorithms. Driver perception–response times and braking levels to the computed FCW alarms were modeled with actual driver alarm response behavior recorded in a previous heavy-vehicle FCW field operational test. Driver RE collision avoidance behavior, both with and without FCW alarm feedback, was then simulated with a Monte Carlo simulation approach. The simulation assumed that drivers selected the optimal braking response in the event that multiple FCW alarms were triggered. The number of conflicts avoided and the additional response time available before a crash were then used to assess the safety benefits. This study estimated that FCW systems may afford a 21% reduction in heavy-vehicle RE crashes, which translates to 4,800 crashes per year on U.S. highways.
Rearview Video System as Countermeasure for Trucks' Backing Crashes
Authors: Lee Chanyoung , Kourtellis Achilleas , Lin Pei-Sung , Hsu Peter
Published: February 2011

In general, the operation of large trucks involves many different types of maneuvers. The backing maneuver, in particular, requires a higher level of driver attention because of the limited rear view. A growing number of trucks in the United States are equipped with a rearview video system (RVS) that can help the driver see much of the area behind the vehicle. An RVS consists of one or more cameras and one monitor. It is expected that an RVS can help drivers reduce potential backing crashes. To evaluate the effectiveness of the system, this study performed a controlled driver test with 45 truck drivers. The test used three backing maneuvers and a pedestrian dummy for observation of potential crashes. The results showed that the use of an RVS increased the stop rate of the drivers during the straight-line backing maneuver by 46.7%, which could be interpreted as an increase in the odds of avoiding potential backing crashes during the backing maneuver. The stop rate increased 4.4% and 17.8% for the offset right backing and alley dock backing maneuvers, respectively. Driver age, commercial driving experience, and experience with an RVS showed no statistical association with the increased stop rate, which means an RVS can be adopted by drivers quickly. In general, drivers showed positive attitudes toward using an RVS, and more than 90% of respondents agreed that an RVS could reduce the rear blind spot for large trucks.
Rating Roads for Motorcyclist Safety
Authors: Daniello Allison , Swanseen Kimberly , Mehta Yusuf A. , Gabler Hampton C.
Published: February 2011

Motorcycles are vastly different from other vehicles on the road: they are highly unstable and provide little protection to users. Because of motorcycle instability, variations in road surfaces and geometry may be more hazardous to motorcyclists than to other road users. Road safety ratings for the entire vehicle fleet, primarily cars, have been applied to roadways in Europe, the United States, and Australia. However, these primarily car-oriented systems have limited value for motorcyclists. This study develops a unique road safety rating system designed for motorcyclists. On the basis of normalized motorcycle crash rates, roads were classified into five safety rating categories, ranging from low risk to severe risk. The new methodology for rating roads was applied to 16 roads in New Jersey, covering 1,099.5 mi (1,769.5 km) of road. Roadways were mapped to create a visual representation of the distribution of safety hazards on the analyzed roads. Of these roads, 19% posed a severe risk to motorcyclists. The majority of the roads mapped (27%) had a medium risk for motorcycles. The statewide crash risk mapping was supplemented by an in-depth site investigation of an area known to be particularly hazardous to motorcyclists, to develop a better understanding of potentially dangerous roadway conditions.