bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanistic-Based Model for Predicting Reflective Cracking in Asphalt Concrete–Overlaid Pavements
Authors: Owusu-Antwi Emmanuel B. , Khazanovich Lev , Titus-Glover Leslie
Published: April 2007

One of the most common types of pavement on the national highway system is composite asphalt concrete (AC) over portland cement concrete (PCC). With a large percentage of PCC pavements either approaching or at the end of their design lives, AC overlay of PCC pavements has become one of the most common methods of rehabilitation. This has resulted in several thousand kilometers of composite AC/PCC pavements. As the level of heavy truck traffic loading continues to increase on a majority of pavements, it is likely that the total length of composite pavements in the nation will continue to increase considerably in the coming years. A common type of distress that occurs on these composite pavements is reflective cracking. This occurs when the joints or cracks in the underlying PCC pavement reflect through the AC overlay. A performance model that can be used to predict accurately the amount of reflective cracks in composite AC/PCC pavements has enormous potential uses. The development of a mechanistic-based performance model for predicting the amount of reflective cracks in composite AC/PCC pavements is described. Data from the Long-Term Pavement Performance database were used to develop the model. Using the principles of fracture mechanics, it is illustrated that a mechanistic-based model can be developed that closely models the real-life behavior of composite pavements and predicts the amount of reflective cracks. Because of the mechanistic nature of the model, it is particularly effective for performance prediction for design checks and pavement management. Also, since the model can take into account the relative damaging effect of the actual axle loads in any traffic distribution, it has great potential for application in cost allocation.
Integer Programming of Maintenance and Rehabilitation Treatments for Pavement Networks
Authors: Li Ningyuan , Haas Ralph , Huot Michel
Published: April 2007

A new approach to multiyear maintenance and rehabilitation (M&R) optimization programming for pavement network management is discussed; the approach can be used to help highway agencies make strategic decisions in choosing the optimal investment for their pavement networks. The M&R treatments are standardized in terms of costs, benefits, and performance impacts on the existing pavements. Each standardized pavement treatment strategy, ranging from minor and routine maintenance to major rehabilitation or reconstruction, is defined by its effect and improvement on the existing pavement serviceability. The optimization model is a cost-effectiveness-based integer M&R programming on a year-by-year basis. The objective of the optimization system is to select the most effective M&R projects for each programming year. The optimization system can also be used to calculate the minimum budget requirements for maintaining a prescribed level of the pavement network performance or serviceability. In such a case, sensitivity analysis can be performed to evaluate the annual budget effect on individual pavement performance. The prediction of individual pavement deterioration is modeled as a time-related (nonhomogeneous) Markov transition process. The investigation described was primarily concerned with integration of the performance prediction model, the standardized M&R treatments, and the network optimization process. The principle and methodology developed can be applied to different levels of pavement network management. Finally, a sample application of the integrated pavement optimization model is demonstrated.
Automated Procedure for Generation of Creep Compliance Master Curve for Asphalt Mixtures
Authors: Buttlar William G. , Roque Reynaldo , Reid Brian
Published: April 2007

For the design of asphaltic paving mixtures under heavy traffic loading, the Superpave system specifies use of performance-based mixture tests and prediction models to supplement volumetric mix design procedures. Central to the mechanics-based thermal cracking model used in Superpave is the prediction of thermally induced stresses based on a master curve and shift factor concept. The original version of Superpave had procedures for automated construction of the mixture creep compliance master curve from measured mixture properties. However, recent studies have indicated the need for several new modeling techniques, the development of which has resulted in the need for substantially more sophisticated procedures for automated construction of the master curve. This paper details the development of a computer program called MASTER, which automates master curve construction using built-in logic capabilities designed to handle the wide variety of measured responses encountered in practice. MASTER was found to agree closely with manually determined shift factors for 36 field mixtures investigated. The program was also found to be extremely robust, producing rational shift factors even when used to analyze complicated, thermally damaged materials. On the basis of these findings, the procedures developed here are recommended for inclusion in future revisions of the Superpave performance modeling software.
Issues in Using Jack Human Figure Modeling Software To Assess Human-Vehicle Interaction in a Driving Simulator
Authors: Burnette Charles , Schaaf William
Published: April 2007

The strengths and weaknesses of a leading human figure modeling software when applied to real-time modeling and assessment of human-vehicle interaction in a driving simulator are described. The Jack human figure modeling software, developed at the Center for Human Modeling and Simulation at the University of Pennsylvania, is being applied by the Advanced Driver Interface Design/Assessment Project at the Graduate Program in Industrial Design, the University of the Arts, Philadelphia, to (1) model human-vehicle interactions in driving scenarios before implementing the scenarios in a driving simulator, (2) model the anthropometry of actual drivers in relationship to an accurate computer model of the vehicle interface, (3) capture real-time human-simulator interaction in a dynamic model of human movement and visual attention during a driving episode, (4) select and manipulate discrete objects and behaviors within the model, and (5) replay the model with anthropometric data representing a hypothetical driver population. The difficulties and benefits encountered when trying to use the software and the work under way to develop integrated procedures and tools to support dynamic modeling and analysis of human-vehicle interactions are outlined as an introduction for researchers considering the use of interactive human modeling and simulation software in the assessment of human factors in complex operating environments.
Micromodel for Objective Estimation of Driver Mental Workload from Task Data
Authors: Zeitlin Lawrence R.
Published: April 2007

Observation of driver performance during a 58 000-km (36,000-mile) field study of van pooling indicates that a good estimate of mental workload can be made from an analysis of objective performance data alone. Drivers traversed a mix of rural secondary roads, limited-access expressways, high-density, limited-access urban drives, and downtown city streets on a daily commute from upstate New York to New York City. Data included road characteristics, time, traffic density, speed, weather, brake applications, subsidiary task performance, and subjective difficulty ratings. Driving workload had two components, a steady-state load dictated by road conditions, speed, and traffic density and a transient load determined by the degree of uncertainty in the driving situation. Brake actuations represent the uncertainty inherent in driving while the log2 of the speed is a first approximation of the steady-state information processing load imposed by tracking requirements of vehicle control. Unpredictability of traffic appeared to be the major determinant of perceived difficulty. Workload homeostasis occurred as drivers modified their performance to keep workload within a comfortable range. An objective workload index of the general form, workload = f (brake actuation rate + log2 speed) based on this micromodel of driver behavior predicts subjective driving difficulty. An analysis of variance shows that the workload index distinguished between road types at the p < .0001 level of significance. The workload index correlates at r = .74, 18(df), with the subjective driving degrees of freedom difficulty ratings and at r = .81, 18 df, with the mental workload estimates of the best subsidiary task.
Development of Quality Control/ Quality Assurance Specifications by Using Statistical Quality Assurance for Asphalt Concrete Pavements in California
Authors: Dobrowolski Joe , Bressette Terrie
Published: April 2007

Since 1992, the California Department of Transportation (Caltrans) has been working to improve quality in construction contracting and ultimately the quality of the product provided to the public. In 1996, Caltrans implemented quality control/quality assurance (QC/QA) specifications for asphalt concrete paving. These specifications require contractor QC and provide rewards or penalties based on statistical quality analysis of eight quality characteristics. These specifications were developed through a joint Caltrans/industry group and are supplemented with a QC manual. They were introduced through presentations to user/producer groups, appointment of district QC/QA coordinators, and training for engineers. In March 1996 the first project using QC/QA specifications for asphalt concrete went to bid and in the first year six projects were completed with them. Early projects were for the most part successful. Throughout 1996-1997, the specifications, the QC manual, and the implementation program were reviewed. Revisions to the specifications have been developed. The specifications and manual, issues, recommendations based on the 1996 projects, changes Caltrans has made for the continued use of QC/QA for asphalt concrete, and anticipated additional endeavors in the areas of QC/QA and materials testing are discussed here.
Postliquefaction Deformation of Embankments and Effects on Restraining Piles
Authors: Liam Finn W.D.
Published: April 2007

There are three levels of analysis for assessing the postliquefaction stability of embankments: limit equilibrium analysis using residual strength, Newmark sliding block analysis using residual strength, and finite element large strain displacement analysis. The first two types are well known and often used. In recent years, finite element analysis has been used increasingly for important projects involving life safety and large remediation costs. The application of finite element analysis is illustrated by two case histories—failure of a river protection dike in Japan, and the seismic safety evaluation and subsequent remediation of Sardis Dam in Mississippi. The latter example is particularly relevant to pile-supported abutments because the upstream slope of the dam was nailed to a stable foundation layer using prestressed concrete piles. The determination of the static and dynamic moments and shears in these piles would not have been possible without the finite element analysis. A crucial problem affecting the reliability of all methods of analysis is determining the appropriate value for the residual strength.
Permanent Rotational Deformation of Dry Cohesionless Slopes Under Seismic Excitations
Authors: Siddharthan Raj V. , El-Gamal Mahmoud
Published: April 2007

Simplified methods of analysis are proposed for estimating earthquakeinduced rotational deformations of dry, medium-dense, cohesionless soil slopes of heights ranging from 4 to 10 m. The primary factors that control deformation are acceleration history, amplification (or deamplification) of ground motion, slope geometry, and nonlinear soil properties. The proposed approach accounts for all of these factors. The permanent slope rotation along a circular failure surface is obtained by a procedure similar to Newmark’s sliding block model. The influence of vertical acceleration on the rotational slope deformation was revealed to be very minimal. Simple relationships were developed on the basis of the extensive database generated from the 1994 Northridge earthquake motions to estimate the rotational slope deformation. The relationships presented require readily quantifiable input parameters and can be used, in many cases, as a first approximation for evaluating rotational slope deformation.
Differential Movement at Embankment-Bridge Structure Interface in Illinois
Authors: Long James H. , Olson Scott M. , Stark Timothy D. , Samara Emile A.
Published: April 2007

Settlement of roadway pavement surfaces near highway bridge abutments often leads to abrupt grade differences at the abutments. These grade differences subject vehicles to a bump, which may lead to driver discomfort and potentially unsafe driving conditions. Furthermore, differential movement requires costly and repeated maintenance work that usually impedes the flow of traffic. The sources of differential movement in Illinois can be divided into six major categories: ( a) compression or erosion of materials at the approach embankment-abutment interface, ( b) a broken approach slab, ( c) compression of foundation soils, ( d) compression or internal erosion of embankment soils, ( e) poor construction grade control, and ( f) areal distortion of foundation soils. An approach gradient equal to or greater than 1/100 to 1/125 appears to cause rider discomfort and therefore is proposed as a criterion for initiating remedial measures.
Innovative Method for Evaluating Drilled Shaft Foundations for St. Croix River Bridge
Authors: O’Neill Michael W. , Person Gary J.
Published: April 2007

To develop design parameters for axially loaded drilled shafts for the St. Croix River Bridge, a major river crossing at Oak Park Heights, Minnesota, load tests were conducted on half-scale sockets in the primary formation, the Franconia Sandstone, at a site on the west bank of the river. The test results were analyzed by using a procedure that considered dilatancy at the shaft-sandstone interface using the known normal, lateral stiffness of the rock, and several candidate interface roughness patterns. The normal stiffness was measured by splitting a short socket vertically with an Osterberg load cell, within the Franconia formation. The interface roughness patterns were varied until the load-deformation behavior of the axial socket test was matched. The production shafts will have larger diameters and will penetrate the formation to a shallower depth than the axial test socket. The lateral stiffness therefore was scaled to account for these effects, and the analytical method was used to determine values of side resistance that should be used for designing the production shafts.
Nondestructive Diagnosis of Drilled Shaft Foundations
Authors: Olson Larry D. , Aouad Marwan F. , Sack Dennis A.
Published: April 2007

Nondestructive methods based on propagation of sonic and ultrasonic waves are being used increasingly in the United States and internationally for forensic investigations of existing structures and for quality assurance of new construction. Of particular interest is the quality assurance of newly constructed drilled shaft foundations. Many state departments of transportation specify nondestructive testing of drilled shaft foundations, particularly for shafts drilled and placed under wet construction conditions. For quality assurance of drilled shaft foundations of bridges, the crosshole sonic logging (CSL) and sonic echo and impulse response (SE/IR) methods routinely are used. In the CSL method, access tubes are installed in the shaft before concrete placement. SE/IR measurements require that the top of the shaft be accessible after concrete placement. Proper test setups, specifications, and case studies are presented to illustrate the advantages and disadvantages of each of these methods. Also presented are recommendations for repair when a defect is identified in a drilled shaft foundation. The CSL method is more effective for locating defects. CSL measurements are effective for determining anomalies and defects between two access tubes. However, an accurate image of the defect cannot be determined from a CSL test alone. The crosshole tomography (CT) method uses multiple CSL logs with varying receiver locations to produce a two-dimensional image of the defect. The CT method is discussed and a dataset obtained from a drilled shaft foundation is presented. CT data collection and analysis require more time than the CSL method, and the CT method is used only for critical drilled shaft foundations.
A Real-Time Simulation Environment for Evaluating Traffic Signal Systems
Authors: Bullock Darcy , Catarella Alison
Published: April 2007

Features and operating modes of the current generation of actuated controllers have evolved to the point where there is a significant difference between the configuration parameters associated with an actuated controller and the information obtained from traffic signal system optimization packages such as TRANSYT 7F and PASSER II. As a result, TRANSYT 7F and PASSER II give no guidance on the impact or sensitivity of many actuated control parameters on a traffic signal system’s performance. Furthermore, none of the current generation of microscopic simulation models is detailed enough to evaluate the effect particular features, such as cycle transition algorithms or return from preemption algorithms, have on overall system performance. To address this need, an enhancement made to the CORSIM package that allows physical controllers to be connected to CORSIM is described in this paper. In this arrangement, CORSIM provides the microscopic simulation and tabulation of measures of effectiveness (MOEs). However, instead of CORSIM emulating controller features, CORSIM sends detector information to the physical controllers and reads back phase indications. This type of simulation is often referred to as hardware-in-the-loop. Since CORSIM tabulates performance MOEs, qualitative before-and-after measurements can be obtained for any hardware conforming to the NEMA TS-1 electrical standard for phase outputs and detector inputs. To validate the performance of this hardware-in-the-loop approach, an evaluation is presented that shows there is no evidence of a significant statistical difference in MOEs between the internal control algorithm and the hardware-in-the-loop control algorithm for both a fixed time and actuated controller.
Prediction Models for Truck Accidents at Freeway Ramps in Washington State Using Regression and Artificial Intelligence Techniques
Authors: Awad Wael H. , Janson Bruce N.
Published: April 2007

Three different modeling approaches were applied to explain truck accidents at interchanges in Washington State during a 27-month period. Three models were developed for each ramp type including linear regression, neural networks, and a hybrid system using fuzzy logic and neural networks. The study showed that linear regression was able to predict accident frequencies that fell within one standard deviation from the overall mean of the dependent variable. However, the coefficient of determination was very low in all cases. The other two artificial intelligence (AI) approaches showed a high level of performance in identifying different patterns of accidents in the training data and presented a better fit when compared to the regression model. However, the ability of these AI models to predict test data that were not included in the training process showed unsatisfactory results.
Seasonal Variations in the Age-Related Collision Risk of Ontario Drivers
Authors: Smiley Alison , MacGregor Carolyn , Chipman Mary , Kawaja Kathy , Tasca Leo
Published: April 2007

Studies of age-related collision risk have not considered how collision risk varies by season. In 1994, the Ministry of Transportation of Ontario conducted an exposure survey which gathered year-round data to ensure that seasonal variations in collision risk could be measured and analyzed. Three-day trip logs were mailed to a stratified random sample of 11,250 Ontario drivers. The logs were mailed out at the rate of 938 per month. The survey was conducted from December 1993 to November 1994. The mean daily kilometrage for six age groups was estimated, and seasonal collision rates per 1 million km driven were calculated. Drivers aged 80 to 89 show the most dramatic fluctuations in collision risk. The winter collision rate of 22.4 is over three times higher than the rate observed in the fall (6.7). The collision rate in spring (13.4) is twice that observed in the summer and fall. When the youngest and oldest age groups are compared, it is evident that the collision risk of 80- to 89-year-old drivers is 2.0 times higher in winter and about 1.5 times in spring. The youngest drivers, however, have a collision risk that is substantially higher than the oldest drivers in summer and fall.
Applying the Ordered Probit Model to Injury Severity in Truck-Passenger Car Rear-End Collisions
Authors: Duncan Chandler S. , Khattak Asad J. , Council Forrest M.
Published: April 2007

Collisions between heavy trucks and passenger cars are a major concern because of the severity of injuries. This research has two objectives. One is to examine the impact of various factors on injuries to passenger car occupants involved in such collisions. Due to the complex interaction of factors influencing injury levels in truck-car collisions, the ordered probit model is used to identify specific variables significantly influencing levels of injury in two-vehicle rear-end involvements on divided roadways. Another objective is to demonstrate the use of the ordered probit in this complex highway safety problem. A set of vehicle, occupant, roadway, and environmental factors expected to influence injury severity was developed. Given two-vehicle passenger car-truck rear-end collisions, the variables that increase passenger vehicle occupant injury severity include darkness; high speed differentials; high speed limits; grades, especially when they are wet; being in a car struck to the rear (as opposed to being in a car striking a truck to the rear); driving while drunk; and being female. The interaction effects of cars being struck to the rear with high speed differentials and car rollovers were significant. Variables decreasing severity include snowy or icy roads, congested roads, being in a station wagon struck to the rear (as opposed to a sedan), and using a child restraint. With injuries ordered in five classes from no injury to fatalities, the marginal effects of each factor on the likelihood of each injury class are reported.
Exploratory Multivariable Analyses of California Driver Record Accident Rates
Authors: Gebers Michael A.
Published: April 2007

Since 1964 the California Department of Motor Vehicles has issued several monographs on driver characteristics and accident risk factors as part of a series of analyses known as the California driver record study. A number of regression analyses were conducted of driving record variables measured over a 6-year time period (1986 to 1991). The techniques presented consist of ordinary least squares, weighted least squares, Poisson, negative binomial, linear probability, and logistic regression models. The objective of the analyses was to compare the results obtained from several different regression techniques under consideration for use in the in-progress California driver record study. The results are informative in determining whether the various regression methods produce similar results for different sample sizes and in exploring whether reliance on ordinary least squares techniques in past California driver record study analyses has produced biased significance levels and parameter estimates. The results indicate that, for these data, the use of the different regression techniques do not lead to any greater increase in individual accident prediction beyond that obtained through application of ordinary least squares regression. The methods produce almost identical results in terms of the relative importance and statistical significance of the independent variables. It therefore appears safe to employ ordinary least squares multiple regression techniques on driver accident count distributions of the type represented by California driver records, at least when the sample sizes are large.
Conflict Analysis for Double Left-Turn Lanes with Protected-Plus-Permitted Signal Phases
Authors: Tarrall Mark B. , Dixon Karen K.
Published: April 2007

A conflict study evaluated double left-turn lanes with protected-plus-permitted signal phasing. The data collection team observed traffic behavior at four intersections in the metro Atlanta region. Included in the data set are three intersections operating under protected-plus-permitted signal phasing and a fourth intersection with a before and after examination of a protected-plus-permitted signal phase changed to protected-only phasing. The authors calculated the traffic rates for five conflict types and one traffic event unique to double left-turn movements. A statistically significant decrease in traffic conflicts was identified for the before and after comparison site. The study also identifies unique intersection geometry and traffic volumes at each site and compares traffic conflicts associated with the features. The results generally show that the enhanced capacity of double left-turn lane intersections operating under protected-plus-permitted signal phasing may occur at the expense of the safety of the traveling public.
Development of Safety-Based Level-of-Service Parameters for Two-Way Stop-Controlled Intersections
Authors: Lee Soo-Beom , Berg William D.
Published: April 2007

Current methods for evaluating level of service at two-way stop-controlled intersections do not account for safety considerations. One of the most important factors influencing intersection safety is the availability of adequate sight distance. However, current recommended intersection sight distance criteria do not explicitly consider variability in traffic composition, vehicle characteristics, pavement conditions, or driver characteristics such as perception-reaction time and minimum gap acceptance. Research was therefore undertaken to develop and validate a method where the safety of a two-way stop-controlled intersection could be estimated based on parameters such as intersection geometry, traffic volume, pavement condition, traffic composition, and available sight distances. Simulation modeling was used to estimate the frequency of potential conflicts or collisions resulting from sight distance restrictions. The potential severity of the collisions was modeled using kinetic energy principles. A method for incorporating the results into a level-of-service evaluation framework was then developed.
Consideration of Bollard Treatment at Exit Gore Areas
Authors: Hakkert Alfred-Shalom , Gitelman Victoria
Published: April 2007

The efficiency of bollards—soft plastic post delineators which are installed at exit gore areas of some highways in Israel—is considered. The devices are expected to contribute to better arrangement of traffic streams and to reduce erratic vehicle maneuvers at highway exits. The treatment was examined in three ways: (1) a review of current experience concerning delineation techniques and tools for safety enhancement at exit gore areas, (2) a detailed consideration of accidents occurring on freeways with emphasis on specifics relevant to exit area occurrences, and (3) field observations of driver behavior at exit areas before and after bollard installation. The literature review showed that use of bollards for highway traffic arrangements has not been investigated closely, at least over the past 20 years. However, practice demonstrated that different kinds of delineation treatments did contribute to better traffic operations and decreased the number of erratic maneuvers at exit area approaches. A detailed consideration of accidents for two highways revealed that the accidents occurring at “exit” and “on” areas are a major part of interchange area accidents (69 percent), while explicit “gore area crossing” maneuvers appear only in six cases (23 percent of exit accidents). In total, a potential benefit of bollard application could be relevant to 11 percent of the accidents. Field observations of driver behavior were conducted for two sites. The comparison proved a significant reduction in erratic maneuver rates after the treatment: up to 60 percent in daytime and up to 65 percent at nighttime. Finally, the bollard treatment was recommended for use at freeway exits.
Investigation of the Effectiveness of Boulevard Roadways
Authors: Castronovo Salvatore , Dorothy Paul W. , Maleck Thomas L.
Published: April 2007

The state of Michigan has been constructing directional crossovers in the medians of boulevard roadways since the 1960s to alleviate the congestion and interlocking that were occurring at bidirectional crossover locations. The objective of this research is to investigate the safety benefits of divided roadway and directional crossover median designs. An investigation of the mean accident rates of roadways with boulevards compared to the mean accident rates of roadways with continuous center left-turn lanes revealed that there is a significant difference, with boulevard roadways having a lower mean accident rate for those Michigan roadways investigated. Investigation into the difference of the mean accident rates for boulevard roadways with medians of different widths indicated that roadways with medians greater than 9.15 m (30 ft) but less than 18.30 m (60 ft) had the lowest mean accident rate of the three median categories investigated. The difference was significant for most accident types when compared to roadways with medians less than or equal to 9.15 m (30 ft) and greater or equal to 18.30 m (60 ft). The investigation of the accident rates for boulevard roadways with directional and bidirectional signalized crossovers, while not conclusive, indicated that boulevard roadways with direction crossovers had a lower mean accident rate than boulevard roadways with bidirectional crossovers for signalized roadways.
Adult Bicyclists in the United States: Characteristics and Riding Experience in 1996
Authors: Moritz William E.
Published: April 2007

In December 1996, 20 percent (4,712) of the League of American Bicyclists members were surveyed about their cycling experiences during calendar year 1996. The 33 questions included bicycle type and equipment, distribution of bicycle trips by purpose (e.g., work, on-road recreation), total distance cycled, commuting habits, accidents, and demographic data. The survey was designed to update one done by Kaplan in 1975. By the March 31, 1997, deadline over 2,400 (51 percent) had been returned. Of these, 19 percent were rejected due to incompleteness or inconsistent responses, leaving 1,956 valid surveys. The “average” respondent was a 48-year-old, married (66 percent) male (80 percent) professional (48 percent) who rode 4670 km in 1996. Just over 9 percent reported having had a serious crash (resulting in at least $50 of property damage or medical expense) in 1996. Based on the experience reported by these cyclists, the average cyclist in this group could be expected to ride for 11 years before having such a crash. Falls accounted for 59 percent of the incidents, whereas running into a fixed object happened 14 percent of the time. Moving motor vehicles were involved in 11 percent of the crashes and another bicycle in 9 percent. A relative danger index is calculated that shows that streets with bike lanes have a significantly lower crash rate than either major or minor streets without any bicycle facilities (38 and 56 percent, respectively). Multiuse trails have a crash rate about 40 percent greater than would be expected based on the miles cycled on them, whereas cycling on the sidewalk is extremely dangerous.
Development of the Bicycle Compatibility Index
Authors: Harkey David L. , Reinfurt Donald W. , Knuiman Matthew
Published: April 2007

Presently, there is no methodology that is widely accepted by engineers, planners, or bicycle coordinators that will allow them to determine how compatible a roadway is for allowing efficient operation of both bicycles and motor vehicles. Determining how existing traffic operations and geometric conditions affect a bicyclist’s decision to use or not use a specific roadway is the first step in determining the bicycle compatibility of the roadway. The Federal Highway Administration sponsored a study in which a methodology for deriving a bicycle compatibility index was developed. This tool can be used by bicycle coordinators, transportation planners, traffic engineers, and others to evaluate the capability of specific roadways to accommodate both motorists and bicyclists. It is intended to provide practitioners with the ability to assess the bicycle level of service present on existing facilities or on proposed facilities and can be used for operational, design, and planning analyses.
Simplified Estimation of Demand for Nonmotorized Trails Using Geographic Information Systems
Authors: Wigan Marcus , Richardson Anthony J. , Brunton Paris
Published: April 2007

Estimating off-road trail usage by nonmotorized modes is of increasing interest to the transportation community due to the rising importance of both recreational and nonmotorized travel. Demand patterns for two substantial off-road trails in Melbourne, Australia, were examined using survey and modeling methods to establish the potential for higher levels of demand. The two trails were different in two major respects: one was well promoted, well connected, and a destination in its own right; the other had similar potential, but the linkages and promotional activity to market its assets had not yet been undertaken. The characteristics of these two markets were examined using geographic information systems (GIS) methods and demand estimated on a differential basis using GIS tools. The simple method adopted highlighted the critical nature of marketing a connected series of off-road trails as a single unified route and an easily recognized destination area. The study had to be done using existing data, and it provides a means of combining transportation, GIS, and special-purpose off-road trail usage information to estimate potential demand.
Development of a Bike Path Management System for the University of Illinois at Urbana-Champaign
Authors: Gharaibeh Nasir , Wilson Cynthia , Darter Michael , Jones George
Published: April 2007

Bicycle transportation is an integral part of most college and university campuses. Bike network paths thus represent a sizable investment of operational funds for these institutions. The efficiency of bike travel on campuses is very high in that it is quick, accessible, and safe travel for the rider. When maintained in good condition, bike paths offer safety for both the bicycle rider and the pedestrian. The University of Illinois developed a bike path management system that allows the system to be monitored and inspected regularly to promote riding comfort and timely repairs and to avoid excess deterioration and safety hazards. This results in maximizing the bicycle path network to both the university and the rider. Bicycle paths are becoming more integrated into the nation’s infrastructure system. This was shown with the Intermodal Surface Transportation Efficiency Act, which supported bicycle transportation funding. Although the bike path management system presented was developed from campus bike routes, the system can be expanded and benefit communities also. As presented, the bike management system can provide the University of Illinois with a simple, yet effective, means to monitor, maintain, and budget to keep this facility in good condition.
Pedestrian Compliance Effects on Signal Delay
Authors: Virkler Mark R.
Published: April 2007

Pedestrian delay at signalized intersections must often be considered when describing the quality of pedestrian flow in downtown and other busy locations. Pedestrian delay at signals is usually modeled with the assumption that ( a) pedestrian arrivals are random and ( b) pedestrians proceed only when a Walk signal provides the right-of-way. To reduce their own delay, some pedestrians will at times proceed without a Walk indication. The range of delay reductions that pedestrians achieve by violating the pedestrian signal was examined through a field study of 18 crosswalks. Delays experienced by pedestrians were found to be 22 percent lower than those that would be predicted with complete signal compliance. Although relatively small reductions in delay were due to crossings while the signal was effectively red, the majority of delay reduction was due to people who began their crossing during the flashing Don’t Walk phase. The number of pedestrians who entered crosswalks during the flashing Don’t Walk phases was 69 percent of the number who would be expected to arrive at the curb during these periods if arrivals were random. It is inferred that some pedestrians increase their speeds to enter during the flashing Don’t Walk phase, rather than wait for the next Walk interval. A modification to a delay equation was developed to provide an improved estimate of pedestrian delay at signalized intersections.
Use of Signs and Symbols To Increase the Efficacy of Pedestrian-Activated Flashing Beacons at Crosswalks
Authors: Van Houten Ron , Healey Keenan , Malenfant J. E. Louis , Retting Richard
Published: April 2007

This experiment evaluated two strategies for increasing the percentage of motorists yielding to pedestrians at crosswalks equipped with pedestrian-activated flashing beacons. One method involved adding an illuminated sign, with the standard pedestrian symbol next to the beacons. The second method involved erecting signs 50 m before the crosswalk that displayed the pedestrian symbol and requested motorists to yield when the beacons were flashing. Both interventions increased yielding behavior and the effect of both together was greater than either alone. However, only the sign requesting motorist to yield when the beacons were flashing was effective in reducing motor vehicle—pedestrian conflicts.
Information Used by Visually Impaired People While Walking
Authors: Takamiya Susumu , Hamada Shunichi
Published: April 2007

As part of the efforts to help visually impaired people participate in society, tactile ground surface indicators are installed along roadways in Japan. Recent years have observed the beginning of studies of voice guidance along sidewalks. But, for visually impaired people to actually walk alone to their destinations, they must confirm each intersection and continually check their location against a mental map. It is important to conduct studies to clarify how visually impaired people obtain these kinds of information and what forms of information provision (voice guidance) should be provided to support this process. To this end, this research project involved interviews with 20 visually impaired people concerning the information they use when walking and experiments conducted with the help of 12 visually impaired people to find out which locations along sidewalks require voice guidance. The results revealed that as visually impaired people walk, they confirm their location by means of information ranging from unchangeable features, such as facilities along the route and the shape of the sidewalk, to the sounds and smells of shops they pass. Results also indicated that voice guidance should be provided where two four-lane roads intersect, but that if too many voice guidance points are provided close together, visually impaired people might become confused. It is vital that future road improvement planning incorporate the findings of this study to create spaces where visually impaired people can walk safely and comfortably.
Method for Estimating Effect of Traffic Volume and Speed on Pedestrian Safety for Residential Streets
Authors: Davis Gary A.
Published: April 2007

When local governments find that the demand for traffic-calming measures exceeds their available resources, it may be necessary to select the most needful or most promising projects. Since pedestrian-vehicle collisions tend to be rare on local streets, it will usually not be possible to use accident counts to identify high-hazard locations. A deterministic model of a collision between a pedestrian and a vehicle is described and then some of the model’s variables are allowed to be random. The probability of a collision can then be evaluated as the probability of obtaining a set of variable values leading to a collision. Both parametric and non-parametric methods are described and illustrated, including an example in which estimates of the collision probability and the probability distribution of vehicle collision speeds are used to identify promising sites for traffic calming. The methods can be used for any location where an analyst has vehicle spot speed and traffic count data and is able to specify reasonable values for the other model variables.
Analysis of Pedestrian Behavior and Planning Guidelines with Mixed Traffic for Narrow Urban Streets
Authors: Kwon Young-In , Morichi Shigeru , Yai Tetsuo
Published: April 2007

The aim of this study was to examine pedestrian behavior and suggest guidelines for analyzing pedestrian traffic flow in narrow urban streets with mixed traffic. For the analysis of pedestrian behavior, 15 streets around an urban railway station in Tokyo were surveyed, and several parameters were obtained, such as pedestrian paths around stationary obstacles; share of pedestrians using the sidewalk as a factor of street environment and traffic conditions; and influence distance of and for bicycles and cars. With respect to planning guidelines, the authors have simultaneously defined a new index of time-space occupancy ( Qt-si) of traffic modes in mixed-traffic conditions that considers the occupancy of time and space in the time-space diagram. Also, a new concept for level-of-service standards has been suggested for mixed-traffic conditions that employs the concept of time-space occupancy of each mode and hindrance/conflict between modes.
Descriptive Analysis of Crashes Involving Pedestrians in Florida, 1990–1994
Authors: Baltes Michael R.
Published: April 2007

A descriptive analysis was conducted of pedestrian crash data used to categorize pedestrian crashes according to a variety of factors, including pedestrian gender and age, time of day, pedestrian’s contributing cause of crash, injury severity, weather condition, road system identifier, and so forth, to the specific sequence of events perceived to influence the crash. The results reported are based on 5 years (1990–1994) of pedestrian crash data in Florida. The database contained 44,541 or 100 percent of the pedestrian crashes that were reported to law enforcement that occurred in Florida during this period. The process of categorizing pedestrian crashes in the manner described provides a valuable analytical tool for developing effective and practical countermeasures to reduce the deaths and injuries incurred by pedestrians involved in traffic crashes in Florida and elsewhere. Analysis of the pedestrian crash data can provide information about to whom and where, when, and how crashes occur in Florida.
Proposed Holistic Framework for Managing Development of Road Infrastructure Technology in South Africa
Authors: Rust F. C. , Vos R. M.
Published: April 2007

The technology development process for the public sector in the transportation industry in South Africa became fragmented as a result of a short-term view with a lack of strategic focus. The subsequent perceived poor performance of the technology development program and inadequate implementation of results motivated the development of a new model for technology development—utilizing a holistic, systems approach at the strategic level with supporting techniques and basic information. The conceptual development of the new technology development model implemented in South Africa is discussed and the use of some of the concepts in the planning and execution of technology development programs for the Southern African Bitumen Association (Sabita) and the South African Department of Transport (SADoT) are illustrated. It is concluded that technology transfer and implementation would be much more effective if it were conducted as part of the technology development system.
Evaluation of Stability, Nature of Modifier, and Short-Term Aging of Modified Binders Using New Tests: LAST, PAT, and Modified RTFO
Authors: Bahia Hussain U. , Zhai Huachun , Rangel Andres
Published: April 2007

In a recent survey of users and producers of modified asphalts, stability and short-term aging were two of the main concerns regarding the use of modified asphalts. In an NCHRP project, a concentrated effort was put into development of revised or new testing procedures to better characterize the nature of modified asphalt and to solve some of the difficulties with using existing aging procedures developed for neat asphalts and modified asphalts. Three main procedures have been proposed to complement the existing Superpave procedures: the laboratory asphalt stability test, for measuring the storage stability of asphalt binders; the particulate additive test, for separation of particulate additives; and the modified rolling thin film oven test for short-term aging. The background behind the development of these test methods is explained, and typical data collected for a number of modified asphalts are presented. The results indicate that these tests show high promise in covering characteristics not covered by the current Superpave binder specifications and in solving some of the problems with the existing aging methods. The results also indicate that the behavior of modified binder can be very complex and that the method of data interpretation is very critical.
Dynamic Analysis-Based Approach To Determine Flexible Pavement Layer Moduli Using Deflection Basin Parameters
Authors: Lee Yung-Chien , Kim Y. Richard , Ranjithan S. Ranji
Published: April 2007

Most of the deflection analysis programs used today to analyze falling weight deflectometer (FWD) data are based on static analysis, which often underestimates the subgrade strength. Unfortunately, dynamic analysis usually involves complex calculations and requires significant computation time, thus making it impractical for routine applications. A methodology based on deflection basin parameters and artificial neural networks (ANN) for processing dynamic FWD measurements to estimate layer strengths is presented in this paper. Two-dimensional, dynamic finite element analysis using the ABAQUS program was employed to develop the deflection information for this study. Unlike the majority of the existing backcalculation programs that iteratively adjust the layer moduli to match the measured deflections, the proposed method first determines the subgrade modulus by means of two deflection basin parameters—Base Damage Index and Shape Factor F2—and then applies the estimated subgrade modulus and other parameters as input variables to a trained ANN to estimate the upper layers’ moduli. In contrast to other programs that require the input of seed values for layer moduli, this method does not require initial estimates as input. A set of field FWD measurements were analyzed both by this method and by the MODULUS program. Results reveal that the proposed method is able to better predict the asphalt concrete layer modulus while taking into account the dynamic effects of the FWD test. This method is also shown to be computationally efficient, which makes it applicable for routine tasks and field use.