bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanistic Approach to Pavement–Vehicle Interaction and Its Impact on Life-Cycle Assessment
Authors: Akbarian Mehdi , Moeini-Ardakani Seyed Sina , Ulm Franz-Josef , Nazzal Munir
Published: February 2013

The accuracy and the comprehensiveness of any pavement life-cycle assessment are limited by the ability of the supporting science to quantify the environmental impact. Pavement–vehicle interaction represents a significant knowledge gap that has important implications for many pavement life-cycle assessment studies. In the current study, the authors assumed that a mechanistic model that linked pavement structure and properties to fuel consumption could contribute to closing the uncertainty gap of pavement–vehicle interaction in life-cycle assessment of pavements. The simplest mechanistic pavement model, a Bernoulli–Euler beam on a viscoelastic foundation subjected to a moving load, was considered. Wave propagation properties derived from falling weight deflectometer time history data of FHWA's Long-Term Pavement Performance program were used to calibrate top-layer and substrate moduli for various asphalt and concrete systems. The model was validated against recorded deflection data. The mechanistic response was used to determine gradient force and rolling resistance to link deflection to vehicle fuel consumption. A comparison with independent field data provided realistic order-of-magnitude estimates of fuel consumption related to pavement–vehicle interaction as predicted by the model.
Limits of Agreement Method for Comparison of Pavement Friction Measurement
Authors: de León Izeppi Edgar , Flintsch Gerardo W. , McGhee Kevin K.
Published: February 2013

Previous comparisons of pavement friction equipment focused on the harmonization of devices that measure pavement friction, but did not assess the agreement of the measurements between them. Harmonization was accomplished with normalization of the measurements through adjustment to a standard slip speed and use of macrotexture measurements in models of the friction–speed relationship. A problem with this procedure was that the true value of friction on which the comparisons were made was assumed. When true values remain unknown, valid comparisons between two devices require the use of agreement assessments. Limits of agreement (LOA) were used to compare two pavement friction devices. The first comparison was made with one run to illustrate LOA. A second comparison with two runs was made to gain understanding of their repeatability and use in LOA. A more complex LOA procedure was conducted with multiple runs of the two devices. The results of another study that used LOA between another pair of pavement friction devices showed a better agreement. The obtained LOA results showed a 95% confidence level, which was considered not adequate. A comparison between the 95% repeatability coefficients and the 95% LOA computed for the two devices indicated that factors other than repeatability were responsible for the lack of agreement. Use of the LOA method of analysis should be considered before harmonization of different devices. Predictive models based on correlation are not recommended for comparing pavement friction measuring devices.
Sensitivity of Commuters’ Demographic Characteristics to License Plate Data Collection Specifications: Case Study of I-85 High-Occupancy Vehicle to High-Occupancy Toll Lanes Conversion in Atlanta, Georgia
Authors: Khoeini Sara , Rodgers Michael O. , Elango Vetri Venthan , Guensler Randall
Published: February 2013

The demographic characteristics of commuters are significant determining factors in many transportation-related policy and planning decisions. A popular way of obtaining the demographic characteristics of roadway system commuters is through license plate studies. There is a concern, however, that data collection factors including time, day, and location of data collection can potentially affect the observed demographic characteristics of the collected samples. This study uses statistical tests to assess the sensitivity of observed demographic characteristics from license plate data collection to data collection parameters by using data collected in the I-85 high-occupancy vehicle corridor in the Atlanta, Georgia, metropolitan area.
Short-Term Travel Time Prediction considering the Effects of Weather
Authors: Qiao Wenxin , Haghani Ali , Hamedi Masoud
Published: February 2013

Reliable travel time prediction enables both road users and system controllers to be well informed about future conditions on roadways so that pretrip plans and traffic control strategies can be made to reduce travel time and relieve traffic congestion. The objective of this research was to use traffic and weather data from multiple data sources to develop an integrated model that could predict travel times under various weather conditions, especially severe weather conditions. Prediction models are compared, and their performance in case studies is investigated.
Analysis of Travel Time Reliability in New York City Based on Day-of-Week and Time-of-Day Periods
Authors: Yazici M. Anil , Kamga Camille , Mouskos Kyriacos C.
Published: February 2013

Travel time reliability in New York City was analyzed with three travel time reliability measures. A classification and regression tree model was used for the analysis. Instead of analysis of conventional peak and off-peak periods, day-of-week (DOW) and time-of-day (TOD) periods were determined on the basis of each travel time reliability measure. DOW and TOD periods were identified on the basis of average travel time and each selected measure. Travel time reliability measures formulated to explain the same phenomenon classified different periods as having similar characteristics. The results agreed with the literature that reliability measures should be based on temporal periods such as DOW and TOD; however, the selection of time periods should be measure specific. The impact of New York City's urban grid network on travel time and speed distributions is also discussed. The travel time distribution patterns reported in the literature for freeways do not exist for the city. Therefore, caution is suggested for transferring reliability measures across different network structures.
Generating Route-Specific Origin–Destination Tables Using Bluetooth Technology
Authors: Carpenter Charles , Fowler Mark , Adler Thomas J.
Published: February 2013

Bluetooth media access control (MAC) data collection technology has emerged as a forerunner in the suite of passive data collection techniques used in travel time and origin–destination (O-D) data collection efforts because of its low cost, ease of implementation, and richness of the resultant data set. With a few notable exceptions, the majority of published research and practical applications of Bluetooth MAC data to date have focused on travel speed analysis. This paper aims to add to the existing literature on Bluetooth O-D data research by describing an analytic approach used to develop route-specific O-D tables for a 15-mi corridor in Jacksonville, Florida. The data from this project were successfully used as an after-model validation tool for base and future year toll revenue forecasts. Bluetooth MAC data were shown to provide a robust and rich data set capable of providing insight into the travel patterns of users in a corridor that would not be easily or efficiently achieved with other data collection methods. The paper also seeks to provide practical guidance and insight into successfully deploying and analyzing Bluetooth MAC data.
Comparative Evaluation of Reported Speeds from Corresponding Fixed-Point and Probe-Based Detection Systems
Authors: Chase R. Thomas , Williams Billy M. , Rouphail Nagui M. , Kim SangKey
Published: February 2013

Point-based traffic sensors, such as microwave radar and acoustic sensors, provide the valuable capability of sampling the entire traffic stream. However, full network coverage with point sensors requires a significant initial capital investment and ongoing maintenance expenditures. Probe-based sensors can cover an extensive roadway network at a much lower cost because roadway-based field equipment is not required. Decisions regarding the relative level of point sensor- versus probe-based deployment for traffic monitoring involve evaluating the trade-off between the value of comprehensive detection versus total system costs. An essential step in evaluating this trade-off involves directly comparing collocated point sensor and probe vehicle systems to understand how the derived traffic stream measures from the two approaches differ. This study compared 5-min speeds from microwave radar and acoustic sensors with link speeds from Global Positioning System (GPS) probes for both directions at five freeway locations. Systematic differences were found at one location. Floating car GPS runs were performed to confirm that the systematic error lay in the point speeds. The speed differences at all sites were normally distributed, with three locations indicating a mean speed difference greater than 5 mph. Nonsystematic speed differences were identified; the difference was more than 1.5 standard deviations lower than the mean difference. This difference may indicate inherent inaccuracies in reported GPS speeds under heavy congestion, including instances of time lag in recovering from congested speeds.
Estimation of Multiclass and Multilane Counts from Aggregate Loop Detector Data
Authors: Yuan Yufei , Wilson R. Eddie , van Lint Hans , Hoogendoorn Serge
Published: February 2013

Lane utilization on the highway is affected subtly by dynamic traffic management systems such as speed controls and lane management. To optimize the operation of dynamic traffic management, a better understanding of lane utilization is required, in particular, of how the flows of different vehicle classes (e.g., passenger cars, lorries) vary across the carriageway. Most loop detector systems do not collect this multilane, multiclass count data. This study developed a procedure for estimating multilane, multiclass counts from a variety of standard aggregate loop data formats from around the world. The estimation procedure involved the inference of multilinear regression laws that relate multilane, multiclass data to standard aggregate formats. The regression laws were then trained with small samples of individual vehicle data on a site-by-site basis. Preliminary results showed that the estimation procedure worked rather well, even when the input data were minimal—the extreme case being that of (U.S.-style) single-loop data, for which only flow and occupancy were available on a by lane basis. An error analysis indicated that small amounts of individual vehicle data were sufficient to train the estimator, provided they contained a representative mix of the flow behaviors at the site in question. Further work is required for the practical development of the tool, but it appears to have a wide range of potential uses for both researchers and practitioners.
Comparison of Modeling Approaches for Imputation of Video Detection Data in Intelligent Transportation Systems
Authors: Castrillon Felipe , Guin Angshuman , Guensler Randall , Laval Jorge
Published: February 2013

Gaps in real-time and archived traffic data are common and can be attributed to several factors, such as sensor failures and data communications interruptions. Regardless of the cause of the missing data, these gaps often must be filled with reliable and accurate estimates before the data can be used for planning, operations, or congestion-mitigation purposes. This research compared different methods for imputing missing values in video detection system data, including historical averages, simple linear regression, multiple linear regression, spatial averages, and Newell's simplified kinematic wave model. The study used the fundamental relationship between speed and flow in filtering the data for quality control. A sensitivity analysis tested the response of different methods to factors such as the size of training data set and time-of-day adjustments to the algorithms. The results indicated that the time of day and volume adjustment factors had a nontrivial impact on the accuracy of the outputs. Despite significant errors in the base data set, the Newell algorithm performed on a par with the other methods in terms of bias and mean absolute percentage, but the more simple factoring methods provided comparable results and were easier to implement.
Advances in Uncertainty Treatment in FHWA Procedure for Estimating Annual Average Daily Traffic Volume
Authors: Gecchele Gregorio , Rossi Riccardo , Gastaldi Massimiliano , Kikuchi Shinya
Published: February 2013

This paper proposes an approach that estimates annual average daily traffic (AADT) of a road section from incomplete data. This approach improves the accuracy and interpretability of the results while preserving the concept of the current FHWA procedure. When the short-period traffic count (SPTC) of a road section is given, a road group with a known AADT and a similar traffic pattern is identified. The AADT of the road section in question is estimated by adjusting the AADT associated with the road group by the degree of similarity. The uncertainty associated with the similarity is measured by nonspecificity and discord. The model was tested with data obtained in the Province of Venice, Italy. The analysis considered the characteristics of SPTC, including duration and day of the week. Estimates obtained with the proposed method and two existing methods were compared. The proposed method was found to produce more accurate results than the previous methods. Weekday 48-h short counts were found to be the best sample SPTC for AADT estimation. Furthermore, the measures of uncertainty helped to interpret the quality of the estimates. SPTCs with a lower value of discord were found to yield better AADT estimates, and a high value of nonspecificity indicated uncertainty with respect to matching with the groups. These measures can also indicate the need for additional data collection.
Estimating Traffic Speed with Single Inductive Loop Event Data
Authors: Lu Xiao-Yun , Varaiya Pravin , Horowitz Roberto , Guo Zhaomiao , Palen Joe
Published: February 2013

The estimation of traffic speed based on loop detector occupancy is a long-standing problem that is critical to traffic management and control. Single-loop detector stations are still popular in highway traffic systems in practice. Although dual loop stations could generate more accurate speed estimation with event data, updating single loops to dual loops is costly. Most previous work, such as the g-factor method on speed estimation with a single-loop system, used aggregated data and assumed a known effective vehicle length. However, those methods did not always produce good results, particularly in traffic transition phases. This paper proposes a new approach using event data and mode occupancy within a moving window of variable length to estimate the effective vehicle length, or g-factor. Berkeley Highway Laboratory dual loop data with a 1-Hz update rate and 60-Hz information were used for algorithm validation and reliability tests. The speed estimated from the corrected dual loop data was used as the ground truth for comparison. Root mean square error was used to quantify the discrepancy. Results showed that the proposed approach generates very satisfactory speed estimations compared with estimations from dual loop stations. This algorithm can be run at the control-cabinet level, in which event data of an individual loop from a 170 or 2070 controller are available without the need of any hardware modification. These controllers have the processor capabilities to handle data in real time.
Experimental and Numerical Study of Cable Anchorage for Cable-Supported Bridge
Authors: Lu Chun-Yang , Wu Chong , Zhou Hong-Min
Published: February 2013

In this study, a 1:2 scaled-model experiment of a cable anchorage was performed. The data collected from the experiment were analyzed, and a finite element analysis (FEA) shell model was described and compared with the experimental results to estimate the level of residual stress and to study its influence together with stress concentration. The ultimate capacity and the failure mode were discussed further to clarify the mechanical behavior. The research showed that residual stress was high on some local areas of the anchorage; residual stress and stress concentration would influence local stress distribution but would have little impact on global behavior. FEA was not a perfect substitute for experiments because of the inaccuracy of its stress results in local areas subject to residual stress and stress concentration. Global behavior and ultimate capacity from elastic–plastic FEA were reliable, however. Judging from the plastic strain and the area of yielding region, other than local maximum stress, the failure mode of the cable anchorage was not the local yielding of the diaphragm but the complete yielding on the anchor plate.
Impact Forces from Heavy-Vehicle Collisions with Bridge Piers
Authors: Brackin Michael S. , Abu-Odeh Akram , Buth C. Eugene , Williams William F. , Fry Gary T. , Freeby Gregg
Published: February 2013

Guidance on how to design a bridge pier for heavy-vehicle impact is limited. AASHTO's Load and Resistance Factor Design Bridge Design Specifications cites a 400-kip design load but no detailed methodology to apply it. Furthermore, the magnitude was established on the basis of a limited set of data. This paper presents detailed analyses of bridge piers under heavy vehicular impacts, which were performed at the Texas A&M Transportation Institute. With the use of finite element analyses, the impact force was quantified with respect to pier diameter, vehicle type, total vehicular mass, and ballast type (i.e., rigid or deformable). In addition, a full-scale crash test was performed with an 80,000-lb tractor trailer, which hit an instrumented pier to quantify the impact force and its distribution. Analysis of the test and the simulation concluded that a 600-kip load was appropriate as the recommended design load for a bridge pier exposed to heavy-vehicle impacts. In addition, researchers at the Texas A&M Transportation Institute recommended application of the load 5 ft above ground and 0° to 15° from the pavement edge.
Use of Strain Data to Estimate Remaining Fatigue Life of a Fracture-Critical Bridge
Authors: Fasl Jeremiah , Helwig Todd , Wood Sharon L. , Frank Karl
Published: February 2013

A fracture-critical steel I-girder bridge was instrumented with strain gauges to estimate the remaining design fatigue life. The two girders on the bridge had extensive fatigue cracking. Continuous, dynamic strain data were collected for nearly 2 months to determine an effective stress range and cycle count according to Palmgren–Miner's rule. A simplified rainflow counting algorithm was developed and used to calculate the amplitude of each fatigue cycle. The effective stress range and cycle count were combined with AASHTO's S (stress range)-N (number of cycles to failure) curves to estimate the remaining design fatigue life of certain bridge details. The data revealed that the estimated design fatigue life was exceeded in the east girder (right lane), whereas some life remained in the west girder (left lane). The distribution of observed cracks in the girders was closely correlated with the calculated fatigue life. A method is presented in this paper to index the effective stress range so that strain measurements can be compared over extended periods.
Acoustic Emission Method for Real-Time Detection of Steel Fatigue Crack in Eyebar
Authors: Johnson Michael B. , Ozevin Didem , Washer Glenn A. , Ono Kanji , Gostautas Richard S. , Tamutus Terry A.
Published: February 2013

After the discovery of a significant crack in an eyebar (fracture-critical element) on the San Francisco–Oakland Bay Bridge in California, the California Department of Transportation (Caltrans) explored possible remote monitor solutions to provide the greatest possible safeguards for the some 200,000 vehicles that used the bridge daily. Caltrans selected an acoustic emission (AE) monitoring system that allowed the detection and localization of crack initiation and growth in real time. The AE method relies on the propagation of elastic waves released by a sudden stress–strain change at the crack tip. The challenge of the AE method in a field application is the disturbance of the data by extraneous noise sources. A robust damage detection algorithm is required to differentiate relevant damage data from secondary noise sources, such as friction. Caltrans required that the proposed monitoring solution be validated through laboratory testing. This paper presents the full-scale laboratory testing of two eyebars loaded under constant amplitude fatigue to detect and locate crack growth under intense friction-type noise sources with use of the AE method. Verification is presented of AE results with ultrasonics testing, dye penetrant, and visual methods to detect damage. Linear location accuracy with simulated signal sources is discussed. The pattern recognition algorithm to differentiate noise signals and crack growth signals is presented. On the basis of this study, the AE method will be used to continuously monitor 384 eyebars with 640 AE sensors on the San Francisco–Oakland Bay Bridge.
Cost-Efficient and Innovative Design for Bridge Approach Slab
Authors: Thiagarajan Ganesh , Ajgaonkar Sheetal V. , Eilers Michael G. , Halmen Ceki
Published: February 2013

Concrete bridge approach slabs (BASs) are used at the interface between bridge abutments and pavements that rest on compacted embankment. The objective of the research presented here was to develop optimal-cost BAS designs for new and replacement slabs. Two solutions presented here included (a) cast-in-place (CIP) design for new construction and (b) novel, precast, prestressed (PCPS) slab designs for new construction and replacement of BASs. The practices of state departments of transportation (DOTs) with respect to BASs were evaluated and compared with those of the Missouri DOT. On the basis of the practices, a 20-ft span was chosen and finite element models were analyzed to consider different slab lengths, thicknesses, and loss of support conditions to calculate maximum moments, deflections, and end slopes. On the basis of predicted values, CIP and PCPS design alternatives were recommended. Recommended alternatives were estimated to have a lower cost and a performance equal to or better than the current Missouri DOT designs. A new study has been initiated in which the recommended BAS designs are to be implemented in the field.
Need for Bridge Monitoring Systems to Counter Railroad Bridge Service Interruptions
Authors: Otter Duane , Joy Richard , Jones Mary Clara , Maal Luis
Published: February 2013

This paper describes an effort to understand the types of railway bridge irregularities that cause service interruptions and to use this information to evaluate the need to develop bridge monitoring systems. Existing monitoring systems and other mitigation techniques were also considered. The study described in this paper considered the frequency and severity of such service interruptions and estimated that the annual risk exposure from bridge irregularities cost tens of millions of dollars; the estimate did not include the cost of consequent train delays. The analysis showed that the largest contributors to irregularities were scour and other bridge hydraulic issues. The next most frequent causes were strikes from marine traffic and strikes from highway traffic. Other large contributors were damage by derailed trains, fire, failed structural members, and movable bridge irregularities. The number of train delays from structural failures was minimal, primarily because of effective inspection and maintenance procedures implemented by North American railroads. A risk control matrix was developed to match potential irregularities with existing control measures and to identify those areas in which additional controls might be warranted. Results suggested that track displacement detectors, tilt monitors, and midspan displacement monitors should undergo additional investigation. Bridge inspection is an effective way to avert many potential losses and presents an opportunity for railway workers to detect defects as well. Workers trained to recognize bridge-related irregularities may be a cost-effective way to reduce losses from bridge service interruptions.
Live Load Distribution of Hybrid Fiber-Reinforced Polymer Composite Superstructure on the Basis of Field Test
Authors: Ahn Il-Sang , Park Younghoon , Chen Stuart S. , O'Connor Jerome
Published: February 2013

Transverse live load distribution in a concrete–fiber-reinforced polymer (FRP) composite hybrid bridge was investigated both experimentally and analytically. The subject bridge was a concrete–FRP composite hybrid bridge, constructed with four 31-ft (9.4-m) long, prefabricated superstructure panels, which were joined along longitudinal field joints made of steel-reinforced grout. The live load distribution factors (DFs) of this bridge were evaluated with strain values measured in field tests and produced from finite element analysis. Design documents and load rating reports showed that a simplified method on the basis of beam-bending could be used in the design process, which required live load DFs. From strain values measured during load tests, the DFs were inferred to be 0.35 and 0.49 for interior and exterior panels, respectively. The comparison of load tests done 6 years apart indicated no significant change in the structural performance of the bridge. Although the design of this structure was unique, the evaluation showed that other hybrid structural members also could achieve good load distribution. The investigation indicated that composite structures could be durable with little maintenance required.
Analytic Hierarchy Process to Improve Simple Bridge Security Checklist
Authors: Valeo Meghann , Nassif Hani , Issa Layla , Capers Harry , Ozbay Kaan
Published: February 2013

Enhancement of bridge security is key to improved homeland security and entails several steps, including on-site assessment, analysis of security components, and implementation of some mitigation measures. A review of the nation's current bridge security posture showed a need to develop methods to identify critical bridges as security hazards and to provide engineering standards and guidelines for security design to reduce the vulnerability of bridges to attack. In particular, a need was seen for a simple bridge security checklist to provide on-site assessment of bridge vulnerability and security risk. After the events of September 11, 2001, the New Jersey Department of Transportation asked Rutgers University to develop a checklist to be used by bridge inspectors to provide management with security data for the department's entire bridge inventory. Rutgers developed a concise checklist, which consisted of yes or no questions in three categories: occurrence, vulnerability, and importance. The overall risk of a structure was measured in terms of an equation risk. To improve this tool, a survey was administered to industry subject matter experts across the United States to determine the relative importance of each question. The data from the survey were analyzed with the use of the analytic hierarchy process, and new weights were assigned to each question. This paper provides the results of the survey and discusses the methodology, analysis of the survey results, and implementation of the updated tool.
Does Use of Formal Tools for Road Safety Management Improve Safety Performance?
Authors: Elvik Rune
Published: February 2013

The use of 10 formal tools for road safety management in 18 European countries was surveyed by means of a questionnaire sent to national highway agencies. Use of the management tools was found to vary. An attempt was made to determine whether a relationship existed between use of the tools and safety performance. The basic hypothesis was that the more extensive use a country made of the safety management tools, the better would be its safety performance. Four statistical analyses were made to test this hypothesis. Results were ambiguous, but no clear support for the hypothesis emerged. However, the study has serious limitations and is essentially inconclusive. It nevertheless identifies an approach that might give clearer results if the study is replicated in a larger sample of countries.
Road Safety Analysis in the United States
Authors: Alluri Priyanka , Ogle Jennifer
Published: February 2013

The Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users required each of the states to develop a strategic highway safety plan and establish a Highway Safety Improvement Program (HSIP) as a core program. The HSIP required states to submit annual 5% reports describing at least 5% of their most hazardous locations, approaches being used to improve safety at these locations, and their effectiveness in improving safety. A review of FHWA's 2009 5% reports indicated that most state departments of transportation were still using basic safety analysis procedures such as frequency, rate, or safety index. Understanding that traditional methods are fraught with issues, biases, and false assumptions, recent research has opened doors to more advanced methodologies in the form of two safety analysis tools: SafetyAnalyst and the Highway Safety Manual (HSM). Unlike basic traditional methods, the empirical Bayes approach used in these tools involves rigorous calculations and requires safety performance functions in addition to roadway characteristics, traffic volume, and crash information. The data requirements and statistical complexity of these new safety tools are considered by many a hindrance to their adoption, but the levels of increasing complexity with additional requirements allow states to adopt at their own speed. The intent of this paper is to document the current engineering-related safety analysis practices and states’ perspectives toward adopting and implementing SafetyAnalyst and the HSM. The perspectives of several states on implementation of SafetyAnalyst were obtained through a survey and are discussed in this paper. This survey mainly helps the practitioners, administrators, and researchers to understand the various engineering-related safety analysis methods used across states and the states’ perceptions on shifting to newer tools.
Pricing for Traffic Safety
Authors: Litman Todd
Published: February 2013

This paper evaluates the traffic safety impacts of various transport pricing reforms, including fuel-tax increases, efficient road and parking pricing, distance-based insurance and registration fees, and public-transit fare reductions. This analysis indicates that such reforms can significantly reduce traffic risk, in addition to providing other important economic, social, and environmental benefits. Crash reductions depend on the type of price change, the portion of vehicle travel affected, and the quality of alternative transport options available. If implemented to the degree justified on the grounds of economic efficiency (for example, to reduce congestion, recover road and parking facility costs, and make insurance more actuarially accurate), these reforms are predicted to reduce North American traffic casualties by 40% to 60%. The low per capita traffic fatality rates in European and wealthy Asian countries result in significant part from their higher transport prices, which result in more efficient multimodal transport systems by which residents drive less and rely more on alternative modes. However, these benefits are often overlooked: pricing reform advocates seldom highlight traffic safety benefits, and traffic safety experts seldom advocate pricing reforms. Taking these steps is particularly important for developing countries now establishing pricing practices that will affect their future travel patterns and therefore crash risks.
Technical Details for Integrating Safety and Planning at Level of Individual
Authors: Miller John S.
Published: February 2013

The need for strengthening the connection between transportation safety and planning has been well documented, and guides have been developed to encourage this integration. When a central Virginia region expressed an interest in performing such integration, beginning with an analysis of existing crashes, an opportunity arose to implement one such guide. This opportunity led to the identification of key details that a transportation planning professional, with the goal of integrating safety and planning, must resolve. Details include the threshold distance that defines a crash cluster, the manner in which disparate geographic systems are used to locate crashes, selection of performance measures to support community programs, and examination of individual crash reports to identify potential countermeasures. The commonality of these details is that they are not ends unto themselves but rather that they support larger objectives associated with integration of safety planning. This paper discusses resolution of such details through a search for a solution that is not necessarily optimal but minimizes computational effort, training needs, and staff time. Because regional planning agencies and state departments of transportation have limited staff and budgets available for this endeavor and because these details may not be apparent at the outset of a process to link safety and planning, explicit consideration of these decisions may result in agencies performing analyses that otherwise would not be undertaken. Furthermore, it is possible to develop a relatively short training curriculum that is based on these concepts. Given that staff time is increasingly limited, providing just enough information to enable an individual to perform a few what-if scenarios is one way to increase incorporation of safety into the planning process elsewhere. In that sense, these findings suggest lessons for implementation of research results generally.
Spatiotemporal Analysis of Macroscopic Patterns of Urbanization and Traffic Safety
Authors: Kang Sanghyeok , Spiller Margot , Jang Kitae , Bigham John M. , Seo Jongwon
Published: February 2013

This study provides a preliminary investigation into the relationship between urbanization and traffic collisions by analyzing the spatial patterns in Sacramento County, California, from 1998 to 2008 through use of urban land classifications and traffic collision data. The ArcGIS directional distribution tool was used to create standard deviational ellipses to investigate the distributional trend of urban land and traffic collisions over time. Statistical outputs representing changes of geographical centroids, elliptical areas, and standard distances (long and short axes) were then compared. Collisions were also divided into subsets by severity level to account for inherent differences in the spatial distribution of different types of collisions. The results provided insight into the macroscopic spatial patterns of urban land and traffic safety and their relationships. The limitations of the method and the need for further research were discussed. The approach in this study would be useful for other metropolitan areas with similarly changing development patterns and can be helpful in guiding future research that compares these two phenomena.
Method for Estimating Highway Collision Rate that Considers State of Traffic Flow
Authors: Song Sungjun , Yeo Hwasoo
Published: February 2013

Among traffic-related variables, vehicle speed is thought to be a major one closely related to collision occurrence. This study aimed to develop a methodology to estimate a collision rate that considers the traffic state in a freeway section and focuses on speed variables. To define the traffic condition of a section, four section-based traffic states related to the speed of upstream and downstream locations were used. The collisions were classified into three types (rear-end, sideswipe, and other), and two variables (speed difference between upstream and downstream and average speed of upstream and downstream) were considered as independent for standard linear regression analysis. The findings showed that both speed difference and average speed had an influencing effect on the collision rate for each type of collision and traffic state. Rear-end and sideswipe collisions showed a different collision rate pattern than the others, and the influence of the speed difference between upstream and downstream changed with the traffic state. Through regression analysis, rear-end and sideswipe collision rates were expressed by speed difference while other types of collisions were described by average speed. This research can provide a methodology for understanding the collision potential of a highway as it relates to the traffic state and can be widely used for roadway traffic safety improvement.
Exploring Traffic Safety and Urban Form in Portland, Oregon
Authors: Gladhill Kristie , Monsere Christopher M.
Published: February 2013

Urban form affects community development, livability, sustainability, and traffic safety. Urban planners have long assumed a relationship between urban form and traffic safety. That relationship favors designs with fewer through streets because such designs are believed to improve safety. An empirical study to explore this assumed relationship used crash data and an extensive resource of other data to define the urban form. Total reported crashes (21,492) within the city limits of Portland, Oregon, from 2005 to 2007 were aggregated by using a uniform 0.1-mi grid for the spatial unit (n = 792 cells); the crashes were modeled by using negative binomial regression to study the effect of urban form, which was defined by variables that captured street layout, exposure, connectivity, transit accessibility, demographics, and trip making (origins and destinations). These relationships were modeled separately by mode (vehicle, pedestrian, and bicycle crashes), by crash type, and by severity of crash injury. The models found that urban-form variables of street connectivity and intersection density were not significant at the 95% confidence level for vehicle and pedestrian crashes or for different levels of crash severity, in contrast to results in earlier studies. Elasticity estimates for all models were dominated by increases in vehicle miles traveled. Business density, population, and transit stops were significant variables in many models; these results underlined the importance of the design and planning of streets in determining where growth in businesses, employment, and housing will occur so that added traffic volumes can be handled safely.
Procedure for Ranking Unsignalized Rural Intersections for Safety Improvement
Authors: Montella Alfonso , Mauriello Filomena
Published: February 2013

This paper presents a procedure for ranking rural unsignalized intersections that uses quantitative safety evaluations performed as part of the safety inspection process. The procedure might be effective for the selection of cost-effective treatments at intersections and might be quite helpful for administrations that do not have high-quality crash data and for those that manage low-volume roads for which crash data cannot give enough information to help prevent future crashes. The procedure evaluates a safety index (SI) that can be used to rank intersections for further investigation. The SI can be assessed whether crash data are available or not. If crash data are available and their quality is good, the SI can be effectively used in conjunction with the empirical Bayes (EB) estimate of frequency as ranking criteria. If crash data are not available or poor, the SI can be used as a proxy for crash data and becomes the only ranking criterion. Validation of the SI procedure was performed by comparing the results with EB safety estimates. The SI was assessed in 22 three-leg intersections in Italy. In the same intersections, a safety performance function was calibrated and the EB refinement technique was used to obtain a better estimate of existing safety performance. Correlation between SI values and EB safety estimates was highly significant, with 84% of the variation in the estimated number of crashes explained by the SI value. The results from a Spearman's rank correlation show that rankings from the SI and the EB estimate agree at the 99.9% significance level.
Effects of Drivers’ Actions on Severity of Emergency Vehicle Collisions
Authors: Yasmin Shamsunnahar , Anowar Sabreena , Tay Richard
Published: February 2013

Emergency vehicles (EVs) are used to provide essential services to society in the event of an emergency. Hence, crashes involving these vehicles are a concern, and investigating crash characteristics of EVs is the first step toward improving their safety. In particular, the contribution of any improper driver behavior or actions must be identified before (a) a program of behavior modification is recommended to authorities or (b) countermeasures are implemented to improve road safety, or both. This study attempts to identify the driver actions that contribute significantly to the severity of a crash involving at least one EV by using data from the Province of Alberta, Canada, for the period from 1999 to 2008. In addition, the impact of control variables formed from demographic, vehicle, environmental, and behavioral factors will also be explored. The results indicate that drivers’ violations of the road rules significantly contributed to increasing the severity of crashes. Non-EV drivers’ errors, nonrepairable damage to the vehicle, collision of an EV with a two-wheeler, and sun glare were some of the other variables that had significant influence on crash severity.
Young, Inexperienced, and on the Road
Authors: Scott-Parker Bridie , Watson Barry , King Mark J. , Hyde Melissa K.
Published: February 2013

The graduated driver licensing (GDL) program in Queensland, Australia, was considerably enhanced in July 2007. This paper explores the compliance of young learner and provisional (intermediate) drivers with current GDL requirements and general road rules. Unsupervised driving, learner logbook accuracy, and experiences of punishment avoidance were explored as was speeding as a provisional driver. Participants (609 females, 423 males; M = 17.43 years) self-reported their sociodemographic characteristics, driving behaviors, and licensing experiences as learners. Six months later, a subset of participants (238 females, 105 males) completed another survey that explored their provisional behaviors and experiences. Although the majority of participants reported compliance with both the GDL requirements and general road rules, such as stopping at red lights on their learner license, a considerable proportion reported speeding. Furthermore, they reported becoming less compliant during the provisional phase, particularly with speed limits. Self-reported speeding was predicted by the following variables: younger age at licensure, being in a relationship, driving unsupervised, submitting inaccurate learner logbooks, and speeding as a learner. Enforcement and education countermeasures should focus on curtailing noncompliance, targeting speeding in particular. Novice drivers should be encouraged to comply with all road rules, including speed limits, and safe driving behaviors should be developed and reinforced during the learner and early provisional periods. Novice drivers have been found to model their parents’ driving, and parents are pivotal in regulating novice driving. It is vital that young novice drivers and parents alike be encouraged to comply with all road rules, including GDL requirements.
Integrating Parental Attitudes in Research on Children's Active School Commuting
Authors: Yang Yizhao , Markowitz Ezra
Published: February 2013

Current active research on school travel emphasizes travel distance and neighborhood walkability as major environmental conditions affecting the occurrences of children walking or biking to school. The impacts of parental travel attitudes on children's school travel behavior remain understudied. This paper outlines a conceptual framework that incorporates the relationships of attitudes, environment conditions, and children's walking or biking to school. The framework recognizes the predictive power that attitudinal factors have for children's walking or biking to school; the framework also highlights the moderating effects of parental travel attitudes on the predictive power of some environment conditions. By using data (1,197 cases) from a school travel survey conducted in a midsized school district in Oregon, this paper reports that parental attitudes toward walking or biking to school and car use are significant explanatory variables in models predicting occurrence of children walking or biking to school when the models control for important environmental variables. The analysis also reveals that important built environment variables—travel distance to school and neighborhood walkability—exhibit varying levels of impacts on the probability of children walking or biking to school when parents demonstrate different attitudes toward active school commuting and car use. The paper discusses implications of the research findings for the challenges facing Safe Routes to School Programs and explores approaches that can make these programs more effective.
Use of “Your Speed” Changeable Message Signs in School Zones
Authors: O'Brien Sarah Worth , Simpson Carrie L.
Published: February 2013

The Safe Routes to School (SRTS) program, through a variety of tools, seeks to enable children to walk and bicycle safely to school. One such tool recently implemented through a program of the North Carolina Department of Transportation (DOT) is the use of speed feedback signs (“Your Speed” signs) to reduce vehicle speeds in school zones. The North Carolina DOT has no policy or standard for the use of these signs within school zones, and research illustrating the value of using permanently installed “Your Speed” signs in school zones is sparse. The Eastern Carolina Injury Prevention Program (ECIPP) applied for SRTS funding to install these signs as part of its education, encouragement, and enforcement project. The North Carolina DOT therefore initiated a study on the use of the signs in conjunction with ECIPP's larger SRTS project. Significant findings of this study include a 3.0 mph (p < .0001) to 4.5 mph (p < .0001) reduction in speed sustained over a 12-month postinstallation period, suggesting that responses to “Your Speed” signs may not diminish as drivers become accustomed to the signs’ presence. On the basis of these promising results, the North Carolina DOT is considering additional research to inform policy considerations fully for the future use of such signs. This research may be useful for organizations seeking innovative SRTS program tools to improve speed compliance in school zones, contemplating the use of speed feedback signs in school zones but needing information on their effectiveness, and having interest in a different way to evaluate their own SRTS projects.