bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Horizontal Curvature on Single-Vehicle Motorcycle Crashes along Rural Two-Lane Highways
Authors: Schneider William H. , Savolainen Peter T. , Moore Darren N.
Published: February 2011

Motorcycle crashes and fatalities have been increasing rapidly during the past 12 years both in Ohio and across the rest of the United States. In response to these issues, various studies have examined aspects of motorcycle safety in recent years. However, there has been limited research on the effects of site-specific roadway geometry on the frequency of motorcycle crashes, particularly at nonintersection locations. Typically, researchers employ Poisson and negative binomial crash prediction modeling techniques in these types of studies. The research presented in this paper uses a negative binomial model, applying full Bayes methods to improve model performance and to assess the impacts of horizontal curvature and other geometric features on the frequency of single-vehicle motorcycle crashes along segments of rural two-lane highways. The data used in this study include crash records for the years 2002 through the spring of 2008, in combination with available geometric design information, for those curves maintained by the State of Ohio. The analysis data set includes 30,379 horizontal curves that experienced a total of 225 motorcycle crashes during the study period. The findings show that the radius and length of each horizontal curve significantly influence the frequency of motorcycle crashes, as do shoulder width, annual average daily traffic, and the location of the road segment in relation to the curve.
Risk-Based Highway Design
Authors: Ismail Karim , Sayed Tarek
Published: February 2011

Existing geometric design guides provide deterministic standards for design requirements primarily based on near worst-case scenarios and conservative percentile selection of design parameters. Probabilistic geometric design analysis has been advocated to represent realistically the randomness in design parameters and variables. Probabilistic techniques can provide a measure of the degree of deviation from design standards. Collision modification factors have been advocated as quantitative measures of the impact on safety associated with changes in road features or traffic control. Often, however, no collision modification factors exist in the literature to predict the safety impact of changing particular road features. An important example is sight distance restriction on horizontal curves. Many highways in British Columbia, Canada, are located in mountainous terrain where the additional cost of earthwork or land acquisition to accommodate lateral road expansion can be prohibitive. In this constrained environment, a typical trade-off arises between design requirements (e.g., adequate sight distance on a horizontal curve) and budgetary constraint. The resolution requires comparing the consequences of every alternative. In these cases, reliability analysis can be used to evaluate the risk of deviating from the design requirements. A decision-support tool was developed to compare the risk of different deviations from sight distance requirements. Two case studies were used to investigate the safety implications of sight distance limitation on road segments, the risk associated with deviation from standards, and risk variations among the road segments. The proposed road design is associated with relatively high risk of limited sight distance, and the risk levels associated with standard design requirements vary significantly.
Effect of a New Cross-Section Design on Low-Volume Roads
Authors: Richter Thomas , Zierke Benedikt
Published: February 2011

The standard designs of rural roads vary significantly and show several failures that negatively affect road safety. Many low-volume roads (local roads, average daily traffic <3,000 vehicles) are designed especially inappropriately. One approach to achieving a high-quality road network is the standardization of certain road types that are supposed to have similar road characteristics within their category but show significant differences from the other road types. In the development of the new guidelines of rural roads in Germany, low-volume roads are displayed by a single-lane cross section to make them distinguishable from common highways (identification of low-volume roads). The effects on the driving behavior induced by the new cross-section design are described. Empirical analysis was used in with-and-without and before-and-after studies to evaluate road sections. The new single-lane cross sections for low-volume roads showed positive results. The before-and-after study showed that the average driving speed could be reduced and the lane shifted toward the middle of the road by installing the new road markings. This effect was shown on both real roads and on the driving simulator. Furthermore, the new road marking does not result in a lower safety standard for situations with oncoming traffic, because in potentially critical situations, the lane-keeping profiles in both directions still have enough space in between each other. Overall, the indication of design classes has positive effects on driving behavior and, therefore, the safety level on roads.
Truck Acceleration Speeds and Distances at Weigh Stations
Authors: Gattis J. L. , Bryant Micah A. , Duncan Lynette K.
Published: February 2011

Tractor-trailer trucks accelerating on freeway entry ramps and entering the main traffic lanes require greater lengths to accelerate than do passenger vehicles. As freeway volumes have grown over the decades, entry ramp junction designs that were once adequate now experience congestion at weigh stations and other locations where higher volumes of trucks enter the freeway. The acceleration lengths and speeds of tractor-trailers accelerating onto freeways were measured at five vehicle weigh stations. Other data obtained and analyzed included truck weights, freeway volumes, and freeway grades. Models were developed to predict tractor-trailer speed over given acceleration lengths. From the analysis, it was concluded that longer acceleration lanes were needed for heavy vehicles leaving weigh stations to accelerate to speeds closer to the speeds on the main lanes and to be less disruptive to freeway traffic flow as the heavy vehicles merge into the main lanes. The findings also have implications for establishing the location of weigh stations, the spacing of freeway interchanges, and the setting of freeway speed limits.
Optimum Urban Clear Zone Distance
Authors: Sax Christian R. , Maze Thomas H. , Souleyrette Reginald R. , Hawkins Neal , Carriquiry Alicia L.
Published: February 2011

Urban communities often have limited amounts of right-of-way available for establishing a setback distance from the curb for fixed objects. Urban road designers must weigh the cost of purchasing additional right-of-way for clear zones against the risk of fixed-object crashes. From 2004 to 2006, fixed-object crashes made up 15% of all fatal urban crashes and 3% of all crashes in the state of Iowa. Many states use AASHTO recommendations as minimum clear zone standards, whereas other states have increased the required minimum clear zone distance, but little research exists to support the specification of these minimums. The effects of the clear zone on safety performance of urban curbed streets were studied. The study included synthesizing selected state practices and investigating the benefits of various clear zone widths on the basis of 13 urban corridors in Iowa. The results suggest that a 4- to 5-ft clear zone could be effective in reducing 90% of urban fixed-object crashes and recommend that additional research be conducted to account for variations in speed, traffic, and other corridor characteristics.
Rural Expressway Intersection Design Guidance
Authors: Hochstein Joshua L. , Maze Thomas H. , Souleyrette Reginald R. , Stout Thomas B. , Welch Thomas M. , Preston Howard , Storm Richard
Published: February 2011

A rural expressway is a high-speed, multilane, divided highway with partial access control with both at-grade intersections and grade-separated interchanges. Many state transportation agencies are converting rural two-lane undivided highways into expressways for improved safety and mobility. However, collisions at two-way stop-controlled (TWSC) expressway intersections are reducing the safety benefits that should be achieved after conversion. When the safety performance of these intersections deteriorates, the countermeasure path typically begins with several signing, marking, or lighting improvements, followed by signal-ization, and could ultimately result in grade separation. Signals are not always effective at improving safety and hamper the mobility expressways are meant to provide. Interchanges are not economically feasible at every problematic intersection and can take years to develop; therefore, more design options at TWSC rural expressway intersections are needed. Some state transportation agencies have experienced success with innovative rural expressway intersection countermeasures that are not currently included as design options within national guides. Therefore, NCHRP Report 650: Median Intersection Design for Rural High-Speed Divided Highways, was commissioned to recommend revisions to AASHTO's A Policy on Geometric Design of Highways and Streets (Green Book) and the Manual on Uniform Traffic Control Devices (MUTCD) regarding rural expressway intersection design. Project tasks included summarizing existing expressway intersection design guidance within these national guides, documenting state transportation agency experience with innovative rural expressway intersection safety treatments, and recommending revisions to the Green Book and the MUTCD.
Evaluating the Effects of Freeway Design Elements on Safety
Authors: Park Byung-Jung , Fitzpatrick Kay , Lord Dominique
Published: February 2011

Increased emphasis has been placed on improving the explicit role of highway safety in making decisions on highway planning, design, and operations. This end can be achieved by quantifying the safety effects of geometric design elements for various highway facilities. The objective of this study was to investigate the safety effects of two important design elements for freeways: ramp density and horizontal curve. Data available for use in the evaluation included 324.2 centerline mi of freeways collected in Texas. Five years (1997–2001) of freeway crashes were examined. Negative binomial regression models were used to estimate the effects of independent variables on crashes. The final model for evaluation revealed that crashes on freeway segments were associated with average daily traffic, on-ramp density, degree of curvature, median width with inside shoulder, the number of lanes (for urban freeways), and whether the freeway is in an urban or rural area. Off-ramp density was not statistically significant in the model. Furthermore, the effect of on-ramp density on freeway crashes was significant for horizontal curves but not for tangent sections and indicates that freeway designers should eliminate or minimize the number of on-ramps within the horizontal curves. The statistical modeling results were geared into the development of accident modification factors for on-ramp density and horizontal curves that can be used for safety prediction of freeways.
Determining Lengths of Left-Turn Lanes at Signalized Intersections under Different Left-Turn Signal Schemes
Authors: Kikuchi Shinya , Kronprasert Nopadon
Published: February 2011

An analytical procedure was developed to determine the lengths of left-turn lanes at signalized intersections. A large body of literature exists about this subject; however, most examine the case when the left-turn and through movements take place during the same signal phase (split phase). Many state departments of transportation base their guidelines on this case also. The general framework was developed for determining the lengths of the left-turn lanes that prevent lane overflow and blockage of the entrance of the left-turn lane by the queued through vehicles. The framework considers many factors: arrival rates and the sequence of left-turn and through vehicles, different signal schemes (the split-phase, permissive-only, protected-only leading, protected-only lagging, and protected-permissive left-turn phases), and intersection capacity. All possible queue patterns (including the leftover from the previous cycle) were identified, and the probabilities of lane blockage and lane overflow were obtained for different combinations of the parameters. The recommended lengths that prevent lane overflow and blockage of more than 95% of the cycles were developed. The lengths suggested by the existing guidelines were useful within certain ranges of combinations of left-turn and through volumes. Suggestions are made for determining the lengths for outside this limited range of combinations. The framework and suggested lengths should be useful for identifying the options of extending lane length or changing the signal scheme to manage lane overflow and blockage and for evaluating the adequacy of the current length.
Limits of Acceptable Rail-and-Post Deflection in Crash-Damaged Strong-Post W-Beam Guardrail
Authors: Hampton Carolyn E. , Gabauer Douglas J. , Gabler Hampton C.
Published: February 2011

The guidelines for the testing of strong-post W-beam guardrail, intended to ensure the safety of errant vehicles, are specified in NCHRP Report 350. A limitation of these tests is that they are always performed on new, undamaged guardrail, whereas guardrail along highways is in a continuous cycle of damage and repair. No tests have ever evaluated the performance of deflection-damaged guardrail. A full-scale, two-part crash test was conducted to evaluate the performance of a guardrail with 14.5 in. (368 mm) of prior crash damage. When this guardrail was struck by a 4,409-lb (2000-kg) pickup truck traveling at 62 mph (100 km/h), the vehicle vaulted and came to rest upright behind the barrier. A critical factor was the failure of a post to separate from the rails. Finite element models were used to evaluate the guardrail performance at lower levels of deflection. The crash tests and finite element models demonstrated that rail-and-post deflection of 11 in. (279 mm) or higher resulted in vaulting or rollover. Repair was recommended for strong-post W-beam guardrail with combined rail-and-post deflection exceeding 6 in. (152 mm). This limit allows a margin of safety for variations in soil strength and vehicle height. The existence of rail-only deflection had a minimal effect on the crash performance up to the maximum tested value of 6 in.
Roadway Departure and Impact Conditions
Authors: Albuquerque Francisco Daniel B. , Sicking Dean L. , Stolle Cody S.
Published: February 2011

In-depth accident data were collected to investigate vehicle impact conditions (e.g., crash severity, impact speed, impact angle, and orientation) for crashes with roadside obstacles and features. Descriptive statistics of these variables are presented, including statistics for the data segregated by highway class, speed limit, and access control. Relationships between impact conditions and these segregating factors were explored. Statistical tests were applied to investigate the association between speed and angle, and univariate distributions were fitted for these two variables. Impact speed and impact angle are independent for most highway classes when segregated by highway class, and they have a relatively weak negative correlation. Both impact speed and angle data for all highway classes follow a normal distribution. Joint impact distributions were then determined using the bivariate normal distribution. The findings of this study are of significant importance to the establishment or reinforcement of full-scale vehicle crash testing guidelines, to benefit–cost analysis procedures, and to highway designers who seek more detailed information on probabilities of impact conditions for different highway classes.
Development of Guidelines for Anchor Design for High-Tension Cable Guardrails
Authors: Zhu Ling , Rohde John R.
Published: February 2011

High-tension cable guardrail is becoming increasingly popular in median and roadside applications because of the promise of reduced deflections on impact and reduced maintenance. As the performance of these systems is observed in service, there is a growing concern over the end anchorage foundation performance of current systems. Foundations for high-tension systems must not only be capable of restraining the impact load of a vehicle but must also restrain the initial pretension on the cable system as well as temperature-induced loads. Although it may be acceptable for many roadside safety devices to require foundation repair after impact, foundation failure caused by environmentally induced loads would be a significant maintenance problem. Because initial tension-and temperature-induced loads can be greater than those loads applied during impact, these loadings must be considered in foundation design. Foundation deflection can reduce cable tension, increasing deflection of the system during impact and letting the cables sag after impact. The soil conditions in which these foundations are placed vary significantly. The potential impact, tension, and temperature loads were considered, and a set of suggested foundation designs was developed to accommodate a range of in situ soil conditions. These designs vary significantly in different areas around the nation because of variations in both weather and in situ soil conditions. Deflection during full-scale crash tests may not accurately represent the foundation deflection that will be experienced in the field.
Application of Precast Concrete Barrier Adjacent to Steep Roadside Slope
Authors: Sheikh Nauman M. , Bligh Roger P. , Albin Richard B. , Olson Dave
Published: February 2011

When concrete barriers are installed adjacent to drop-offs or steep roadside slopes such as 1.5H:1V, a cast-in-place concrete moment slab is usually attached to the base of the barrier to resist lateral and overturning forces during vehicle impact. Cast-in-place construction can require more time on-site to build forms, pour the concrete, and allow for curing. This time constraint results in an increase in disruption to traffic and more exposure for construction workers. Furthermore, the installation of a moment slab is very costly and requires an additional construction phase to build the slab. Because the slab is normally under the shoulder and possibly the lanes, the disruption of traffic flow is increased. A new application of a precast 42-in.-tall single-slope concrete barrier for use in front of steep slopes was developed that does not require a moment slab. The lateral movement of the barrier is restricted by embedding it in soil. This design also reduces the embankment behind the barrier to 2 ft. The embedded barrier application was successfully evaluated under Manual for Assessing Safety Hardware Test Level 3 criteria. The permanent deflection of the barrier was 5.5 in. The use of the embedded concrete barrier in lieu of the typically installed barrier with a moment slab is expected to result in cost savings of approximately $300 per linear foot and reduced time to construct.
Improving the Effectiveness of Wayshowing for America's Byways Using Perspective of a Visitor's Eye
Authors: Dahlquist David L. , Eells Jean , Pianalto Curt , Adams Dennis
Published: February 2011

Byway providers—the local staff, organization leaders, and volunteers who sustain a highway's designation as one of America's byways—face challenges of overcoming habituated ways of viewing their byways, especially when these providers offer wayshowing elements of safe travel such as maps, guide signs, directions, and information about traveler services and amenities so that first-time byway travelers can have successful and rewarding byway experiences. The locally based and geographically rich knowledge that byway providers possess is often much more complete than the relatively vague or nonexistent knowledge held by byway travelers and visitors. Byway providers need their intimate geographic knowledge to effectively conserve, plan, promote, and interpret the intrinsic resources of a byway. However, their in-depth knowledge shaped by frequent, habitual experience on their byway can hinder them in developing effective wayshowing materials aimed at assisting nonlocal travelers because the perspective of seeing their byway through a first-time visitor's eye is a difficult one to refocus. Although technical instructions and materials describing how byway providers should assess their guidance systems are valuable, the assessment process often is incomplete if byway providers fail to see apparent needs from a nonlocal traveler's perspective. The America's Byways Resource Center is exploring theoretical models that make concepts about the visitor's experience more explicit and conducting awareness-building exercises designed to help byway providers take more of a visitor's eye perspective. Preliminary assessments of this initiative indicate productive and positive results.
Evaluation of Highway Design Parameters on Influencing Operator Speeds through Casewise Visual Evaluation
Authors: Stamatiadis Nikiforos , Bailey Keiron , Grossardt Ted , Ripy John
Published: February 2011

Designing highways to influence driver operating speed effectively through environmental feedback is a key research field requiring special attention. Virtual reality video simulations were used to record the influence of environmental elements on driver judgments about the appropriate driving speed. This study evaluated the use of various means that could affect operating speeds and affect driver behavior without compromising safety. Data were analyzed through the fuzzy set nonlinear modeling system of Casewise Visual Evaluation methodology to identify design factors that most strongly influenced perceived operator discomfort. The findings indicated that vegetation type and density and barrier type have a significant effect on driver discomfort and thus have the potential to influence operating speeds. Roadway width has a similar effect where narrower roadways increase driver discomfort. The results indicate that roadside features and certain road design elements can be used to affect driver operating speeds.
Evaluation of Maryland Abutment Scour Equation through Selected Threshold Velocity Methods
Authors: Benedict Stephen T.
Published: February 2011

The U.S. Geological Survey, in cooperation with the Maryland State Highway Administration, used field measurements of scour to evaluate the sensitivity of the Maryland abutment scour equation to the critical (or threshold) velocity variable. Four selected methods for estimating threshold velocity were applied to the Maryland abutment scour equation, and the predicted scour to the field measurements were compared. Results indicated that performance of the Maryland abutment scour equation was sensitive to the threshold velocity with some threshold velocity methods producing better estimates of predicted scour than did others. In addition, results indicated that regional stream characteristics can affect the performance of the Maryland abutment scour equation with moderategradient streams performing differently from low-gradient streams. On the basis of the findings of the investigation, guidance for selecting threshold velocity methods for application to the Maryland abutment scour equation are provided, and limitations are noted.
Application of Kozeny–Kovàcs Model to Predict the Hydraulic Conductivity of Permeable Pavements
Authors: Ranieri Vittorio , Antonacci Maria Carmela , Ying Gaoxiang , Sansalone John J.
Published: February 2011

Permeable pavements provide a frictional surface for vehicles during rainfall runoff and function as a porous infrastructure interface, allowing the infiltration and evaporation of rainfall runoff, as well as treatment of pollutants when designed for solute and particulate separation. The hydraulic conductivity (ksat) of permeable pavement is an important hydraulic property. A series of empirical and pore structure models using constant head and pore-based measurements, including total porosity (φt), effective porosity (φe), and pore size distribution indices generated through X-ray tomography (XRT) were used to study permeable pavement. XRT results indicate that the pore matrix is heterodisperse, with φt ≠ φe. Results indicate that the traditional models based on a simple pore structure do not reproduce measured ksat values. More complex pore structure models, even with modification from the original form, gave better results. A modified Kozeny-Kovàcs model was used to reproduce the measured ksat values. The modified model introduces φe and the characteristic pore diameter (De) instead of φt and specific surface area, respectively. Such permeable pavement pore structure parameters with the modified Kozeny-Kovàcs model can be predicted. These results can be useful in the design stage of permeable pavement when a target value of ksat is desired to obtain both friction benefits to improve vehicle safety in wet conditions and to control the infiltration-evaporation of rainfall. The ksat results are combined with continuous simulation modeling using historical rainfall for a Cincinnati, Ohio, highway site on I-75 to provide results illustrating permeable pavement as a low impact development infrastructure component in the highway environment.
Buried Duct Network for Utility Cables along Roads and Highways
Authors: Slavin Lawrence M. , Najafi Mohammad
Published: February 2011

The proposed buried duct network (BDN) for utility cables (e.g., electric power, telephone, cable) represents a departure from conventional buried construction methods of placing cables directly in a trench along the road. The shortcomings of conventional direct-buried construction methods can lead to road damage or safety hazards, including the risk of gas or power line strikes, during reconstruction activities. By contrast, the BDN provides an opportunity for conveniently and safely accomplishing cable upgrades at a low incremental cost to the utilities or their customers. Such a system encourages and supports the installation, maintenance, and expansion of belowground utilities; facilitates their location; and minimizes construction difficulties and hazards, including the proliferation of pole lines. Utility poles represent a significant hazard, often resulting in death and injuries during collisions with motor vehicles. The development of the BDN has been supported and funded by the U.S. Department of Transportation under the Small Business Innovation Research program. The research effort was described at two TRB annual meetings and numerous subsequent industry events. As a result of such broad dissemination of information, accompanied by significant development effort, the basis for the widespread implementation of the BDN has been established, including commercially available hardware and guidelines for its application provided by ASCE. In particular, BDN has been successfully installed in several field trials in permanent applications, confirming its feasibility and demonstrating its overall practicality. BDN helps meet objectives of the national transportation organizations (AASHTO, FHWA).
Incorporating Bicycle and Pedestrian Topics in University Transportation Courses
Authors: Dill Jennifer , Weigand Lynn
Published: February 2011

The focus on context-sensitive design in roadway planning, increased support for addressing public health objectives through transportation and land use planning, and concerns about oil dependence and global warming are growing. Combined, these factors have raised expectations for transportation engineering and planning practitioners to possess more knowledge and skills related to pedestrian and bicycle planning and design. This demand requires more education on these topics. This paper reports on the findings of a survey of 86 university faculty members about the inclusion of bicycle and pedestrian topics in their transportation courses. Of the 134 transportation courses taught by respondents, 59% included bicycle or pedestrian topics, or both. However, because of potential response bias, the findings might be an optimistic assessment of the coverage of bicycle and pedestrian topics in current curricula. Just over half (52%) of the civil engineering courses included only 1 to 2 h of class time on the topics, whereas all of the courses in planning programs offered at least 3 h on the topics. The topics covered most often were pedestrian safety, pedestrian and bicycle planning, and pedestrian and bicycle facility design. At least 43% of the faculty were interested in course materials on pedestrian and bicycle topics that they could incorporate into existing courses. PowerPoint and lecture materials were the most commonly requested types of materials.
Empirical Bayesian Evaluation of Safety Effects of High-Visibility School (Yellow) Crosswalks in San Francisco, California
Authors: Feldman Mark , Manzi Jessica Greig , Mitman Meghan Fehlig
Published: February 2011

The empirical Bayesian method, currently the industry standard for before-and-after collision analysis, was used to perform post hoc tests on the efficacy of high-visibility school (yellow, continental-style) crosswalks in the city of San Francisco, California. Statistical analysis compared the number of collisions predicted for the after period had the enhanced crosswalks not been installed with the number of collisions observed. The analysis used data for 54 treated intersections with high-visibility crosswalks and 54 control intersections, each chosen for its geographical proximity to a treated intersection. The results from this analysis suggest a statistically significant reduction in the numbers of collisions at the intersections with high-visibility crosswalks. The estimated reduction is 37%, with the 95% confidence interval ranging from 13% to 60%. Potential limitations of this analysis, including a constant traffic volume input over time and a background reduction in collisions citywide, are discussed. In addition to the safety benefit attributable to high-visibility crosswalk markings, high-visibility crosswalks likely contribute to a sense of pedestrian comfort and overall design amenity. Future studies would enhance these results by evaluating other factors that may affect pedestrian safety at school crosswalks, such as changes in driver or pedestrian behavior and increased awareness of crosswalks and pedestrian activity.
Safety Effectiveness of Leading Pedestrian Intervals Evaluated by a Before–After Study with Comparison Groups
Authors: Fayish Aaron C. , Gross Frank
Published: February 2011

Strategies to reduce pedestrian–vehicle crashes at intersections should be investigated. Implementation of the leading pedestrian interval (LPI) has been recommended as a strategy for reducing pedestrian–vehicle crashes at signalized intersections; however, research on quantification of the safety effects of the LPI has been limited. Site characteristics, traffic volumes, pedestrian volumes, and crash data were obtained for 10 signalized intersections where the LPI was implemented in State College, Pennsylvania. Similar data were obtained for 14 stop-controlled intersections within the State College area. A before–after with comparison group study design was used to evaluate the safety effectiveness of the LPI implementations. The results suggest a 58.7% reduction in pedestrian–vehicle crashes at treated intersections, which is statistically significant at the 95% confidence level. An economic analysis was also conducted to determine the cost-effectiveness of the strategy. Given the low cost of this strategy, only a modest reduction in crashes is needed to justify its use economically. On the basis of the estimated safety effectiveness, the necessary crash reduction is easily achievable.
Driver and Pedestrian Behavior at Uncontrolled Crosswalks in Tahoe Basin Recreation Area of California
Authors: Mitman Meghan Fehlig , Cooper Douglas , Dubose Brooke
Published: February 2011

For more than 30 years, pedestrian safety studies have considered pedestrian–vehicle collision patterns and pedestrian and driver behavior at marked and unmarked crosswalks at uncontrolled crossings. Recent research in this area, conducted by the University of California, Berkeley, Traffic Safety Center on behalf of the California Department of Transportation (Caltrans), was designed to fill key gaps in the literature by analyzing driver and pedestrian behavior and knowledge of right-of-way laws for marked and unmarked crosswalks. The Caltrans study, as with most previous crosswalk studies, focused on urban and suburban areas (in this case, the San Francisco, California, Bay Area), where driver and pedestrian characteristics do not change significantly from day to day. After this study came the recognition that similar research was needed in rural and recreational locations, where the population frequently changes. As such, this paper summarizes results from field observations of driver and pedestrian behavior at marked and unmarked crosswalks at uncontrolled crossings during the summer in the Tahoe Basin of California. This study, also funded by Caltrans, concludes that the behavior trends identified in the study of urban and suburban areas in the Bay Area are largely similar in a rural and recreational context. This finding is significant for Caltrans, a statewide agency that is seeking to provide a consistent crosswalk installation and treatment policy for its facilities across California. Other regional and state agencies may similarly benefit from the findings of the study.
Relationships and Characteristics of Pedestrian Traffic Flow in Confined Passageways
Authors: Chen Xiaohong , Ye Jianhong , Jian Nanjing
Published: February 2011

Pedestrian traffic flow relationships and characteristics are the key theories used to support the planning and design of walking facilities. For different types of facilities, pedestrian traffic may have a longitudinal flow (unidirectional or bidirectional), cross flow, or multidirectional flow. The present study focuses on longitudinal pedestrian flow in confined passageways. Confined level passageways, ascending stairways, descending stairways, and two-way stairways in Shanghai, China, Metro stations with massive passenger volumes were observed; and data from those locations were collected. Pedestrian flow parameters, including volume, density, and speed, under comparatively full operation states from low density to high density, were acquired by video recording. Overall trends in the relationships between pedestrian volume, density, and speed were analyzed with scatter plots. With full consideration of the significance of the statistical regression results and consistency with reality, models of pedestrian traffic flow for speed–density and volume–density relationships were established for all the facilities observed. The characteristics of the built models in combination with walking behavior, determined by comparison of the differences in the characteristics of walking facilities and traffic operations, are discussed. The collected data, built models, and pedestrian flow characteristics that were revealed could be helpful for improving theories on pedestrian traffic flow and be valuable references to similar studies in the pedestrian context.
Association between Roadway Intersection Characteristics and Pedestrian Crash Risk in Alameda County, California
Authors: Schneider Robert J. , Diogenes Mara Chagas , Arnold Lindsay S. , Attaset Vanvisa , Griswold Julia , Ragland David R.
Published: February 2011

Each year from 1998 to 2007, an average of approximately 4,800 pedestrians were killed and 71,000 pedestrians were injured in traffic crashes in the United States. Because many pedestrian crashes occur at roadway intersections, it is important to understand the intersection characteristics that are associated with pedestrian crash risk. The present study uses detailed pedestrian crash data and pedestrian volume estimates to analyze the pedestrian crash risk at 81 intersections along arterial and collector roadways in Alameda County, California. The analysis compares pedestrian crash rates (the number of crashes per 10,000,000 pedestrian crossings) with intersection characteristics. In addition, more than 30 variables were considered for use in the development of a statistical model of the number of pedestrian crashes reported at each study intersection from 1998 to 2007. After the pedestrian and motor vehicle volumes at each intersection were accounted for, negative binomial regression showed that significantly more pedestrian crashes occurred at intersections with more right-turn-only lanes, more nonresidential driveways within 50 ft (15 m), more commercial properties within 0.1 mi (161 m), and a greater percentage of residents within 0.25 mi (402 m) who were younger than age 18 years. Raised medians on both intersecting streets were associated with lower numbers of pedestrian crashes. These results, viewed in combination with other research findings, can be used by practitioners to design safer intersections for pedestrians. This exploratory study also provides a methodological framework for future pedestrian safety studies.
Automated Analysis of Pedestrian–Vehicle Conflicts
Authors: Ismail Karim , Sayed Tarek , Saunier Nicolas
Published: February 2011

This paper presents a novel application of automated video analysis for a before-and-after (BA) safety evaluation of a scramble phase treatment. Data availability has been a common challenge to pedestrian studies, especially for proactive safety analysis. The traditional reliance on collision data has many shortcomings because of the quality and quantity of collision records. Qualitative and quantitative issues with road collision data are more pronounced in pedestrian safety studies. In addition, little information on the mechanism of action implicated can be drawn from collision reports. Traffic conflict techniques have been advocated as supplements or alternatives to collision-based safety analysis. Automated conflict analysis has been advocated as a new safety analysis paradigm that empowers the drawbacks of survey-based and observer-based traffic conflict analysis. One of the areas of focus of pedestrian safety that could greatly benefit from vision-based road user tracking is BA evaluation of safety treatments. This paper demonstrates the feasibility of conducting a BA analysis with video data collected from a commercial-grade camera in Chinatown, Oakland, California. Video sequences for a period of 2 h before and 2 h after scramble were automatically analyzed. The BA results of the automated analysis exhibit a declining pattern of conflict frequency, a reduction in the spatial density of conflicts, and a shift in the spatial distribution of conflicts farther from crosswalks.
Development and Implementation of a Vehicle–Pedestrian Conflict Analysis Method
Authors: Kaparias Ioannis , Bell Michael G. H. , Greensted John , Cheng Saffier , Miri Ashkan , Taylor Christopher , Mount Bill
Published: February 2011

This paper examines the development, use, and evaluation of a new traffic conflict analysis technique that specifically addresses pedestrian–vehicle conflicts with the intention of being applicable to shared-space environments. The method is based on an existing, well-established, and widely used vehicle–vehicle conflict analysis technique, but is adapted to consider the movement of pedestrians, which differs significantly from that of vehicles. The new method is then implemented on the Exhibition Road site of West London with the use of video data collected from locations with a potentially high concentration of vehicle–pedestrian conflicts, and the results of the analysis are presented. Finally, the results are compared with those obtained by other conflict analysis techniques and also against accident data to assess not only the accuracy but also the functionality of the new technique.
Assessing Use of Pedestrian Crash Data to Identify Unsafe Transit Service Segments for Safety Improvements
Authors: Pulugurtha Srinivas Subrahmanyam , Penkey Eshwar N.
Published: February 2011

This paper assesses the use of pedestrian crash data to explain the role of transit service and ridership in pedestrian crashes in urban areas. The values for measures that may be used to identify segments with transit service where it is potentially unsafe for users to walk were computed to identify the need for safety improvements. Descriptive analysis was conducted by comparing measures such as the numbers of pedestrian crashes, pedestrian crashes per mile, pedestrian crashes per mile per 10 transit stops, pedestrian crashes per mile per 1,000 transit riders (boarding and alighting), and pedestrian crashes per million vehicle miles traveled (MVMT), using data for Charlotte, North Carolina. Thirty study segments with transit service and 30 segments without transit service were considered to compare and examine the relationship. These segments were selected such that the land uses and on-network characteristics were similar and comparable. The computed ratios of the mean values of the numbers of pedestrian crashes, pedestrian crashes per mile, and pedestrian crashes per MVMT on segments with and without transit service were 4.82, 4.92, and 2.70, respectively. Statistical analysis was also conducted to test if the values of the selected measures were significantly higher on segments with transit service than on segments without transit service. Results from both descriptive and statistical analyses support the general belief that pedestrian crash rates are high on transit corridors and that a significant number of these pedestrian crashes involve transit system riders. The values for measures based on pedestrian crash data are thus computed, compared, and combined for segments with transit service to identify segments potentially unsafe for transit system users.
Multimodal Driveway Design
Authors: Gattis J. L. , Levinson H. S. , Gluck J. S. , Barlow J. M. , Eck R. W. , Hecker W. F.
Published: February 2011

Driveways are the link between public roadways and the abutting activities that they serve. Driveways serve a wide range of activities in a variety of contexts. Driveway design guidelines have traditionally focused on accommodating motor vehicles, but in recent years, growing emphasis has been placed on a broader range of issues, such as better managing access and accommodating all modes, including pedestrians and bicyclists. How well driveways are designed affects the safety and mobility of not only motorists but also bicyclists and pedestrians. This paper draws from research performed for NCHRP Project 15–35, Geometric Design of Driveways. It discusses multimodal driveway design considerations and provides design guidelines that recognize the needs of pedestrians (including those with disabilities and transit users) and bicyclists.
Quantifying Bicyclists' Perceptions of Shared-Use Paths Adjacent to the Roadway
Authors: Petritsch Theodore A. , Ozkul Seckin , McLeod Peyton , Landis Bruce , McLeod Douglas
Published: February 2011

This paper documents a study sponsored by the Florida Department of Transportation and conducted to create a model that reflects bicyclists' perceptions of how a shared-use path adjacent to a roadway meets their needs. A user-validated level-of-service (LOS) model for shared-use paths adjacent to roadways (sidepaths) has been created. The resulting model will enable transportation professionals to translate the geometric, physical, and operational characteristics of a sidepath into a reliable LOS measure for the proposed facility. Data for the new sidepath LOS model were obtained from the Video Ride for Science (VRFS) 2009 event, held at the Museum of Science and Industry in Tampa, Florida. The data consist of participants' perceptions of how well roadways met their needs as they viewed video simulations from a bicyclist's eye view on the selected segments. The sidepath LOS model is based on Pearson correlation analyses and stepwise regression modeling of approximately 1,700 combined real-time video perceptions (observations) from VRFS 2009 participants. The study participants represented a cross section of individuals by age, gender, riding experience, and residency. This model has a fairly high correlation coefficient (R2 = .68) with the average observations and is transferable to the vast majority of metropolitan areas in the United States.
Signal Timing Optimization Models for Two-Stage Midblock Pedestrian Crossing
Authors: Ma Wanjing , Yang Xiaoguang , Pu Wenjing , Liu Yue
Published: February 2011

Finding an optimal signal timing plan is one of the most critical operational issues for signalized two-stage midblock crossings, which are increasingly being installed in highly populated areas in developing countries, such as China. In this paper, three signalization control types (simultaneous, progressive, and separate signalization) for two-stage midblock pedestrian crossings are proposed. Both vehicular traffic and pedestrian movements are considered in a unified framework by solving two problems: the optimization of cycle length and the optimization of offsets. The cycle length optimization problem is formulated as a mixed-integer linear programming problem to minimize the cycle length with constraints of the maximum acceptable degree of saturation of vehicle movements, the minimum clearance time, the pedestrian green time, and the maximum number of pedestrians waiting on a central refuge island. The optimization problem of the offset of the two-stage pedestrian signal is also formulated as a mixed-integer linear programming problem to provide the maximum green bandwidth for two successive pedestrian crossings. A VISSIM simulation and a case study in Shanghai, China, were carried out to validate the proposed models. The proposed models are promising in determining the signalization control type and optimizing the signal timings of two-stage midblock pedestrian crossings. Analysis of the sensitivity of the performance of the system was also conducted to assist traffic engineers with selecting appropriate signalization control types and acceptable degrees of saturation. The results from this study offer a basis for traffic practitioners, researchers, and authorities to design and assess signal plans for two-stage midblock pedestrian crossings.
Effect of Pedestrian Safety Retraining for Elementary and Middle School Students
Authors: Gates Timothy J. , Savolainen Peter T. , Datta Tapan K. , Buck Nicholas
Published: February 2011

A pedestrian safety educational training program was presented to more than 930 students in Grades 2 through 7 at five public schools in Detroit, Michigan. Initial student training was performed at four of the schools during spring 2008 and at the remaining school during fall 2008. Retraining was performed 7 to 12 months after the initial training. The same training procedures were used during both the initial training and the retraining sessions. The training program was evaluated with the use of both written pre- and posttesting and before-and-after observations of the street-crossing behavior of children near the schools included in the study. Two measures of effectiveness (MOEs) were used for the evaluation: (a) the violation rate for child pedestrians and (b) the percentage of correct test responses. The child pedestrian violation rate decreased shortly after the initial training; this decrease was sustained for several months. Retraining produced an additional incremental decrease in the child pedestrian violation rate. Initial training also produced increases in the percentages of correct responses between the pre- and posttests for children in all participating grade levels. The increases in correct response percentages were partially sustained several months after the initial training, although measurable decreases in test scores were observed. Retraining provided a statistically significant incremental increase in test scores that negated the decreases observed several months after the initial training. The cumulative impact of initial training combined with retraining was consistently larger than the impact of initial training alone for both the testing and the violation rate MOEs.