bluuebunny/crossref_metadata_2025 huggingface dataset:
Fuzzy Ramp Metering: Design Overview and Simulation Results
Authors: Taylor Cynthia , Meldrum Deirdere , Jacobson Les
Published: April 2007

A fuzzy logic ramp-metering algorithm was designed to overcome the limitations of conventional ramp-metering strategies. The fuzzy controller demonstrated improved robustness, prevented heavy congestion, intelligently balanced conflicting needs, and tuned easily. The objective was to maximize total distance traveled and minimize total travel time and vehicle delay, while maintaining acceptable ramp queues. A multiple-ramp study site from the Seattle I-5 corridor was modeled and tested using the freeway simulation software, FRESIM. For five of the six testing sets, encompassing a variety of traffic conditions, the fuzzy controller outperformed the three other controllers tested.
Investigation of Freeway Incident Characteristics and Their Influence in Planning an Incident Management Program
Authors: Pal Raktim , Latoski Steven P. , Sinha Kumares C.
Published: April 2007

Nonrecurrent congestion caused by highway incidents is a major concern for transportation agencies and millions of road users in most metropolitan areas in the United States. Incidents account for 60 percent of congestion-induced delay. As a low-cost approach to incident management, freeway service patrol programs have gained wide popularity. However, information on freeway incident characteristics is limited. In the current paper, incident data recorded by the Hoosier Helper program in north-west Indiana is analyzed. The distributions of incident frequency and clearance time by incident type and lateral location are reported. The variation of incident rate with time of the day is examined, and the influence of various factors affecting the frequency and clearance time of incidents is explored. Recommendations are made to improve the freeway service patrol program, based on the incident data analyzed. The information provided in this study may be useful for planning similar patrol programs in other metropolitan areas in Indiana and other states.
Exploration of the Breakdown Phenomenon in Freeway Traffic
Authors: Persaud Bhagwant , Yagar Sam , Brownlee Russel
Published: April 2007

Of late, there has been a considerable volume of empirical research on freeway operations during periods of high flow. Part of the motivation for this realm of research is the attractive possibility of increasing flow and speed by preventing breakdown in congested operations. This possibility has been fueled by observations of a “capacity drop,” wherein the discharge flow from the resulting queue is smaller than those observed before breakdown. The research on which this paper is based was aimed at exploring in more detail the implications of metering traffic flow at levels below that at which a breakdown occurs. From this perspective, the nature of precongestion flows is investigated empirically to determine the potential gains from such a policy. The most important contribution is an examination of the likelihood of success of such metering by establishing the probability of breakdown at various traffic flow levels. It is shown, for example, that 1-min median lane flows that are 20 percent larger than queue discharge flows have only a 10 percent probability of breakdown and that 1-min flows equal to the mean queue discharge flows have a negligible probability of breakdown. These results not only have practical significance but also are useful for improving the efficiency of freeway simulation models.
A New Approach to HOV Entry Requirements: MassHighway’s 3+ /Limited 2+ Sticker Program
Authors: Paiewonsky Luisa
Published: April 2007

The Massachusetts Highway Department opened the I-93 Southeast Expressway high-occupancy vehicle (HOV) lane in November 1995, under a three-person, or 3+, entry requirement. A 2+ rule was not implemented because studies indicated that the high number of existing two-person carpools would overload the narrow lane, causing it to fail. While the lane was an operational success, with general public support, the agency fielded continuing complaints about underutilization. In response, the Massachusetts Legislature and MassHighway designed a program to allow a limited number of two-person vehicles into the lane. MassHighway examined the results of the sticker program on incidents, lane violation rates, and HOV volumes. The program’s impact on incidents was negligible, and the rate actually declined slightly in the months following its opening. The program had no impact on the HOV lane’s already low violation rate, which was due to its barrier-protected, limited-acces design. HOV volumes rose 29 percent on average following the opening of the sticker program. Suprisingly, given the high demand for stickers, relatively few recipients use the lane on a regular basis. A MassHighway survey of sticker recipients revealed some of the reasons for this phenomenon and confirmed several operational aspects about the HOV lane in general. The sticker program represents a new solution to an old problem among HOV practioners—how to balance the need for a congestion-free facility, while meeting the need for public acceptance and perception of adequate utilization. The sticker program went a long way toward diffusing public criticism of the HOV lane, while keeping vehicle volumes to a manageable level. The Southeast Expressway HOV sticker program represents one alternative for successfully metering 2+demand.
Vehicular Flow Past Incidents Involving Lane Blockage on Urban Roads: A Preliminary Exploration
Authors: Raub Richard A. , Pfefer Ronald C.
Published: April 2007

The effects of freeway lane reductions on roadway capacity have been discussed in the literature, but only limited attention has been given to capacity reduction on urban arterial roadways. Videotaping of incident management on arterial roadways as part of another project made available data that could be measured and converted into headways. Fifteen incidents involving crashes and disabled vehicles from which measurements were drawn are examined in this report. All events blocked one lane on a four-lane urban arterial. From the data, headways were measured and estimates of vehicle flow rates computed. Overall, an incident blocking one of two lanes on an urban roadway will reduce the idealized flow from the 1,900 vehicles per hour per lane (3,800 vehicles per hour) as suggested in the Highway Capacity Manual by more than 60 percent for crashes and more than 50 percent for disabled vehicles. Crashes resulting in personal injury had a worse-case rate of 1,230 vehicles per hour, or 32 percent of capacity. The lowest recorded flow rate for disabled vehicles was 1,650 vehicles per hour, or 43 percent of capacity. Distribution of headways around crashes were substantially skewed. On the other hand, headways for disabled vehicles tended to cluster around the mean. Differences in headways not only arose from the type of incident but also appeared to be related to the amount of responder activity (e.g., one police officer versus multiple public safety responders) and by the cross-section of the roadway. In the latter case, roadways with painted medians had shorter headways than those with raised medians or painted center lines. More observations need to be made to validate these initial results.
Measuring Traffic Congestion
Authors: Boarnet Marlon G. , Kim Eugene Jae , Parkany Emily
Published: April 2007

A traffic congestion index was developed using data for California highways from 1976 through 1994. The technique yields a congestion measure that has several advantages. The index developed here can be applied to counties, urbanized areas, highway segments, or other portions of geographic areas or highway networks. The index allows cross-sectional and time-series comparisons that have only rarely been possible. What is most important is that the congestion index developed here is based on data that are readily available. The index is compared to others, based on Highway Performance Monitoring System data, and similarities and differences are illustrated. Important issues for future research and data collection efforts that can contribute to more refined congestion measurement are also discussed.
Development and Application of Control Strategies for Signalized Intersections in Coordinated Systems
Authors: Skabardonis Alexander , Bertini Robert L. , Gallagher Brian R.
Published: April 2007

Modern controllers permit traffic signals in coordinated systems to operate as pretimed, semiactuated or fully actuated to improve the traffic performance at the particular intersection or over the total system. Criteria were established for selecting the type of control, and timing strategies were developed for signals in coordinated systems. The proposed strategies were evaluated through simulation on 14 representative real-world arterials and grid networks. Based on the analysis of the simulation results, guidelines were formulated to assist practicing traffic engineers in selecting the most appropriate control strategies at specific intersections in coordinated signal systems. The guidelines were then applied to select the type of signal control at several intersections in the City of Los Angeles. The results from before and after field studies indicate that the recommended control strategies improved traffic performance, and the study guidelines can be used as an operating tool for traffic signal management.
Investigation of National Highway System Roadways in the Highway Safety Information System States
Authors: Zegeer Charles V. , Huang Herman F. , Stewart J. Richard , Williams Carolyn
Published: April 2007

Motor vehicle crash rates and roadway characteristics for National Highway System (NHS) and non-NHS roads in seven states—California, Illinois, Maine, Michigan, Minnesota, North Carolina, and Washington— are presented. Accident and roadway data were extracted from the Federal Highway Administration’s Highway Safety Information System. Overall, crash rates on NHS roads were approximately 10 percent lower than those on non-NHS roads, perhaps the result of higher design standards. Crash rates on urban roadways were considerably higher than on the corresponding rural roadways in each state. For rural roadways, fixed-object crash rates were higher on NHS roads than on non-NHS roads. The distribution of crashes by severity was quite similar on NHS and non-NHS roads. For urban freeways, NHS Interstates usually had lower crash rates than NHS non-Interstates. The majority of NHS roads had lane widths of 3.4 m (11 ft) or more, and many had shoulder widths of 1.5 m (5 ft) or more. Compared to NHS non-Interstate roads, NHS Interstate roads were more likely to have lane widths of 3.7 m (12 ft) or over, shoulder widths of 2.4 m (8 ft) or over, paved shoulders, and improved median design. Highway designers and safety officials can use this type of information about accident rates and roadway characteristics to enhance safety by upgrading existing highways and improving the design of NHS highways to some specified roadway design standards and guidelines.
Safety Benefits of Spiral Transitions on Horizontal Curves on Two-Lane Rural Roads
Authors: Council Forrest M.
Published: April 2007

A vehicle entering or departing a horizontal curve must safely undergo a change in steering angle and a resulting change in side friction forces. The safety-related effects of two alternative designs were evaluated for the “transition” sections of pavement where the curve and tangent meet— a spiral transition, where the tangent and curve are linked by an ever-tightening spiral curve, and a nonspiral transition where the tangent directly abuts the horizontal curve. Using crash and roadway inventory data from over 15,000 transition sections (curve ends) in the state of Washington, contingency table analyses and linear logistic modeling were conducted to explore differences in the probability of one or more crashes on the two types of transitions within each of three types of terrain—level, rolling, and mountainous. At level terrain sites, spiral presence is related to a decrease in crash probability on curve ends with degree of curve greater than approximately 3 degrees. For rolling terrain, a decrease was predicted for all sites on minor arterials and major collectors, and for principal arterial sites with average daily traffic greater than 3,700 vehicles per day. In contrast, in mountainous terrain, an increase in crash probability due to the spiral was predicted for all sites except those with both wider roadway widths and wider shoulders. The models for the mountainous terrain sites did not fit the data as well, indicating the presence of other unmeasured confounding variables.
Accident Models for Two-Lane Rural Segments and Intersections
Authors: Vogt Andrew , Bared Joe
Published: April 2007

Data collected from the states of Minnesota and Washington on rural two-lane highways are used to build accident models for segments and three-legged and four-legged intersections stop-controlled on the minor legs. The quantity, quality, and variety of data collected, together with the advanced techniques applied in the analysis, make this study of special interest. Variables include traffic, horizontal and vertical alignments, lane and shoulder widths, roadside hazard rating, channelization, and number of driveways. Models are of negative binomial and extended negative binomial form and yield R2 values from 0.42 to 0.73 and overdispersion parameters from 0.20 to 0.51. A segment model combining both states and including state as a variable, and intersection models derived from Minnesota data, are featured, along with summary statistics, goodness-of-fit measures, and cross-validation between the states. Segment accidents depend significantly on most of the roadway variables collected, while intersection accidents depend primarily on traffic. The study recommends development of adjustment factors for different regions and times and further development of extended negative binomial models.
Two Problems of Averaging Arising in the Estimation of the Relationship Between Accidents and Traffic Flow
Authors: Mensah Abraham , Hauer Ezra
Published: April 2007

A function linking the expected accident frequency to traffic flow is called a safety performance function (SPF). SPFs are estimated from data for various facilities and accident types. Typically, accident counts over a period of a year or more, and estimates of average flow for such periods, serve as data. The ideal is for SPFs to represent cause-effect regularities. However, because accident counts are for a long time period and because average flows are used, two issues of averaging arise. First, the cause-effect relationship is between accidents and the flows prevailing near the time of accident occurrence. Therefore, ideally, these should be the argument of the SPF. In practice, however, either because of lack of detail or difficulties of estimation, average flows are used for estimation. The question is what problems arise when average flows, such as annual average daily traffic, instead of the flows at the time of the accident are used as the argument of the SPF. This is the argument averaging problem. Second, there are at least two (daytime and nighttime) and perhaps many more cause-effect SPFs that prevail in the course of a year. Ideally, each relationship should be estimated separately. The question is what problems arise if one joint SPF is estimated when two or more separate functions should have been used. This is the function averaging problem. After analysis, how to account and how to correct for the argument averaging problem are shown. At this time, avoiding the function averaging problem by estimating daytime and nighttime SPFs separately can be the only recommendation.
Effects of a Towaway Reporting Threshold on Crash Analysis Results
Authors: Zegeer Charles V. , Huang Herman F. , Stewart J. Richard , Pfefer Ron , Wang Jun
Published: April 2007

The effects on future data analysis capabilities and results should states convert to a towaway and above crash-reporting threshold are quantified. The results from the four states used in the analysis (Illinois, Michigan, Minnesota, and North Carolina) revealed that only 51.7 percent of the crash data would be included using a towaway threshold. Only 33.7 percent would be included using an injury threshold. In general, a towaway threshold would exclude more crashes on urban streets than on rural roads. For most road classes, 40 to 60 percent of crashes would be excluded. A towaway threshold would result in greatly underestimating the occurrence of certain crash types, particularly rear-end, sideswipe, parking, and animal crashes. Run-off-road and angle/turning crashes would also be affected considerably. Using a towaway criterion will seriously affect researchers’ ability to conduct meaningful evaluations of roadside appurtenances, such as guardrail, breakaway signs and poles, crash cushions, and various median treatments. For most vehicle types, only 30 to 60 percent of crashes would be included under a towaway threshold. Technological, institutional, and organizational strategies for improving crash reporting thresholds are suggested.
Allocating the Costs of Motor Vehicle Crashes Between Vehicle Types
Authors: Miller Ted , Levy David T. , Spicer Rebecca S. , Lestina Diane C.
Published: April 2007

When a truck and an automobile are involved in a crash, the harm to occupants tends to vary with the weight of the vehicles involved. In determining the appropriate level of government expenditures for traffic safety, costs in multivehicle crashes involving different vehicle types must be allocated between occupants and nonoccupants of a particular vehicle type. Four methods for allocating costs among different vehicle types are considered, corresponding to different perspectives, including that of occupants of a vehicle and that of society under different property right assignments. Costs based on the four allocation methods for the United States as a whole and per vehicle mile are also estimated. The allocation method was found to have large effects on the relative magnitude of costs.
Police Reporting of Pedestrians and Bicyclists Treated in Hospital Emergency Rooms
Authors: Stutts Jane C. , Hunter William W.
Published: April 2007

Drawing on a study of injured pedestrians and bicyclists treated at hospital emergency rooms in California, New York, and North Carolina, an attempt was made to match the emergency room cases to state motor vehicle crash data, and to analyze the factors associated with the occurrence of a match. The purpose is to (1) provide additional information on the likely level of underreporting of pedestrian– and bicycle–motor vehicle collisions on state crash files and (2) examine whether cases that are reported differ in any systematic way from those that are not reported. A total of 388 pedestrian– and 255 bicycle–motor vehicle cases were available for inclusion in the analysis, with 56 percent of the pedestrian and 48 percent of the bicycle cases matched to state crash files. After adjusting for other potential confounders, pedestrians who were hospitalized or killed were 1.3 times more likely to be reported on the state crash files than were pedestrians receiving emergency room treatment only; those struck in the roadway were 1.7 times more likely to be reported than those struck in nonroadway locations; and those ages 15 to 24 were 70 percent less likely to be reported than pedestrians of all other ages. In contrast, the only factor found to be associated with police reporting of bicycle–motor vehicle crashes was the severity level of the injury: bicyclists who were hospitalized or killed were 1.4 times more likely to be reported on the state crash files than were bicyclists receiving emergency room treatment only.
Predicting Vehicle Occupancies from Accident Data: An Accident Severity Approach
Authors: Chang Li-Yen , Mannering Fred L.
Published: April 2007

Past studies have shown that using accident records to estimate vehicle occupancies (i.e., using the observed occupancies of vehicles involved in accidents) results in an overestimation of occupancy. There are a number of possible reasons for this, one of which is that multioccupant accidents are more likely to be reported (i.e., appear in an accident database) because, with more people, the possibility of an injury is greater. The interaction between vehicle occupancy and accident severity is used to develop a method to correct for the occupancy overestimation bias inherent in accident data. A nested logit model of occupancy and severity is estimated, and a correction technique is applied to eliminate biases. The results show that the proposed approach gives accurate predictions of vehicle occupancies using standard accident data.
Development of Expected Conflict Value Tables for Unsignalized Three-Legged Intersections
Authors: Weerasuriya Sujeeva A. , Pietrzyk Michael C.
Published: April 2007

A high percentage of highway crashes in the United States occur at intersections. These crashes result in property damage, lost productivity, injury, and even death. Identifying intersections associated with high crash rates is very important to minimize future crashes. Identifying the high-risk intersections before crashes occur is a challenge that every traffic/safety analyst faces. Traffic conflict technique is a solution to this problem. Extensive research efforts have been made to estimate mean and abnormal traffic conflict counts at four-legged intersections with varying lane and approach volume conditions. However, similar efforts on unsignalized three-legged intersections have been focused only on two-lane highways. Therefore, a thorough analysis of conflicts at unsignalized three-legged intersections with various lane combinations was necessary. The current study is part of a comprehensive research attempt to develop expected conflict value tables that can be easily used for different intersection configurations. The most common unsignalized threelegged intersection types (total of three) were identified and categorized based on through lanes of the intersection. During the summer of 1995, 12 different traffic conflict types were surveyed from 38 intersections randomly sampled from a five-county area in west-central Florida. Combining a recent 3-year crash history and the collected conflict data of the sampled intersections, new and easy-to-use tables were developed for Florida-based unsignalized three-legged intersections. The tables provide mean, variance, and 90th and 95th percentile conflict rates. These simplified tables can be used to estimate the expected number of crashes, relative safety effectiveness, and operational problems at intersections.
Safety Evaluation of Alternative Signal Head Design
Authors: Sayed Tarek , Abdelwahab Walid , Nepomuceno John
Published: April 2007

A before and after safety evaluation of the installation of a larger signal head design was conducted. The design consists of a 300-mm red light, a 300-mm amber light, and a 300-mm green light, all with 150-W lamps and a yellow backboard with an additional 50-mm reflective border. The signal head design was field tested in 10 urban intersections in British Columbia. The intersections were originally equipped with the standard signal head design consisting of a 300-mm 150-W red light; a 200-mm 69-W amber light, and a 200-mm 69-W green light, with a yellow backboard. An Empirical Bayes before and after safety analysis indicated that the improved signal head design had a significant effect in reducing the overall frequency and severity of accidents at the treatment sites. Accidents were reduced by approximately 24 percent; injury and fatal accidents were reduced by approximately 16 percent. Classical simple before and after techniques were found to overestimate these benefits by approximately one third. It is concluded that increasing traffic signal visibility through the improvement of signal head design is an effective measure of reducing both the frequency and severity of traffic accidents at signalized intersections.
Effect of Environmental Factors on Driver Speed: A Case Study
Authors: Liang Wei Lien , Kyte Michael , Kitchener Fred , Shannon Patrick
Published: April 2007

A case study on the effects of visibility and other environmental factors on driver speed was conducted as part of an intelligent transportation systems field operational test to reduce accidents caused by sudden changes in visibility levels. Baseline conditions established normal vehicle speeds for passenger cars and trucks. Reduced visibility and winds exceeding 40 km/h were found to be the primary factors affecting driver speed.
Spot Speed Analysis on Urban Roads in Riyadh
Authors: Al-Ghamdi Ali S.
Published: April 2007

Nearly 42 percent of traffic accidents on urban roads in Riyadh, the capital of Saudi Arabia, were attributed to speeding. Compared to U.S. data, this developing country has 4.5 times more accidents due to speed. In this study, spot speed data were analyzed using data collected at 13 urban roadway sections in Riyadh. Five of the study sites were freeway sections, and eight were arterial sections. Speed characteristics, including mean, variance, and 85th percentile, were investigated. The study found that obtaining the 85th speed percentile from regression modeling gives much better estimates than those from the normal approximation model. Driver noncompliance with the posted speed limit was clearly shown. At some sites, more than 90 percent of motorists were exceeding the speed limit, indicating that much more active speed limit enforcement is needed.
Operational Analysis of Uninterrupted Bicycle Facilities
Authors: Allen D. Patrick , Rouphail Nagui , Hummer Joseph E. , Milazzo Joseph S.
Published: April 2007

The popularity of bicycles in North America is growing. As the popularity of bicycles has increased, so has the physical network of separate bicycle facilities and designated bicycle lanes in many locations. As a consequence of this growth, there is a demand for more information about bicycle operations on these facilities. Unfortunately, the state of knowledge regarding bicycle operations in the United States currently lags far behind that of motor vehicles and pedestrians. The international research that has been conducted to date regarding bicycle operations on uninterrupted facilities is thoroughly reviewed, and recommended procedures for the operational analysis of uninterrupted bicycle facilities are outlined. The recommended procedures are based on the concept of “frequencies of events” involving a bicyclist and other bicyclists or facility users. Events are defined as bicycle maneuvers required by a bicyclist on a facility, including passings (same-direction encounters) and meetings (opposite-direction encounters). The frequency of events for an uninterrupted bicycle facility is related to the service volumes of bicycles using or projected to be using the facility and does not have to be observed directly. The proposed procedures are, therefore, recommended based not only on their theoretical substance but also on their ease of use by practitioners.
Prediction and Measurement of Travel Time Along Pedestrian Routes
Authors: Virkler Mark R.
Published: April 2007

A methodology to predict the walking and queueing times on pedestrian routes is developed. Walking time predictions are based on either average pedestrian space or flow rate. Queueing time estimates at signalized intersections are based on an assumption of random arrivals. The methodology is tested by comparing travel time predictions with the results of travel time runs on several routes near the city center of Brisbane, Australia. Data from 49 signalized intersections within the routes indicate that upstream coordinated signals can significantly affect downstream signal delay. It was also found that, in a coordinated signal system, the standard deviation of delay at a signal can be much different from what would be expected if arrivals were random. The effect of signal coordination on average delay was also apparent at the arterial level.
Measuring the Safety Effect of Raised Bicycle Crossings Using a New Research Methodology
Authors: Gårder Per , Leden Lars , Pulkkinen Urho
Published: April 2007

Before-and-after study methodology was developed and applied to evaluating the effect on bicyclists’ safety of raising urban bicycle crossings by 4 to 12 cm. In total, 44 junctions were reconstructed in this way in Gothenburg, Sweden. Four of these were studied in detail. Before the implementations, bicyclists were riding either in the roadway or on separate paths parallel to the roadway. The paths then ended with short ramps or curb cuts at each cross street, and bicyclists used nonelevated, marked bicycle crossings, similar to pedestrian crosswalks but delineated by white painted rectangles rather than zebra stripes. The results show that the paths with raised crossings attracted more than 50 percent more bicyclists and that the safety per bicyclist was improved by approximately 20 percent due to the increase in bicycle flow, and with an additional 10 to 50 percent due to the improved layout. However, the increased bicyclist volume means that the total number of bicycle accidents is expected to increase. Besides accident analysis, the change in risk was estimated using four different methods: surveys of bicyclists and experts, respectively; conflict data; and a quantitative expert model. Using a Bayesian approach for combining the results shows that the most likely effect of raising the bicycle crossing is a risk reduction of around 30 percent, compared with the before situation with a conventional bicycle crossing. Motorists and pedestrians also saw safety benefits from this traffic-calming measure.
Sidewalk Bicycling Safety Issues
Authors: Aultman-Hall Lisa , Adams Michael F.
Published: April 2007

Bicycle route and safety data sets for 2,963 commuter cyclists in Ottawa and Toronto, Canada, containing cyclist characteristics, collision and fall history, and regular commute route, are used for this analysis. Previous analyses found sidewalk collisions and fall and injury rates significantly higher on sidewalks than on roads or paths. Of the 52 events reported on sidewalks, none were reported to police and would, therefore, not be found in a police accident database. These events did result in injuries, and in two cases major injuries. This analysis has found that commuter cyclists in Ottawa use sidewalks primarily on major roads (not necessarily high-speed roads) and often to cross bridges or to take shortcuts where no road exists. Toronto commuter cyclists use sidewalks primarily on high-volume multilane roads. Some Toronto cyclists still use sidewalks when bicycle lanes are provided. A slightly higher proportion of women are sidewalk cyclists in Ottawa; however, no age relationship was found. Sidewalk cyclists reported proportionally more near misses with bicycles in the previous month. A relatively large number of sidewalk collisions are with other bicycles. The most significant result of the analysis is that sidewalk cyclists have higher event rates on roads than nonsidewalk cyclists.
Signal Coordination Benefits for Pedestrians
Authors: Virkler Mark R.
Published: April 2007

The potential benefits of reducing pedestrian delay through signal coordination are examined through field data from 10 intersection approaches. The approaches had cycle lengths ranging from 60 to 90 s, walking lengths from the upstream signals ranging from 87 to 105 m, and varying levels of midblock traffic generation. Significant platooning of pedestrians, due to upstream signals, was found on the approaches. This pedestrian platooning could greatly increase or decrease pedestrian delay at the downstream signals, depending on the signal coordination plan. For low green times, the effect of pedestrian platooning on delay was found to be greater than that generally recognized for the automobile mode. Three techniques are described for determining appropriate signal offsets to benefit pedestrians. The first two techniques use average speed and would benefit pedestrians who have speeds that are equal to or greater than the average speed. The third technique determines the delay to be expected from any offset and can, therefore, be helpful in making trade-offs between pedestrian and vehicular delay.
Scramble and Crosswalk Signal Timing
Authors: Virkler Mark R.
Published: April 2007

A variety of methods have been developed for determining appropriate pedestrian crossing times at signalized intersections. Although many of these methods have useful applications, all have significant shortcomings when estimating the crossing time required under high-volume conditions and with two-way flow within a crosswalk. Existing methods are described. A field study conducted to address these shortcomings is then described. The results of the study are used to develop relationships to describe pedestrian flow at signalized crossings. Recommendations are then made to improve the signal timing parameters used for higher-volume pedestrian flows.
Passive Pedestrian Detection at Unsignalized Crossings
Authors: Beckwith Dana M. , Hunter-Zaworski Katharine M.
Published: April 2007

The city of Portland, Oregon, is researching ways to provide safe unsignalized crossings for pedestrians. A concept that shows promise is known as passive pedestrian detection. Passive pedestrian detection is the detection of pedestrians in a stationary or moving state at the curbside of or in a pedestrian crossing by means other than those requiring physical response by the pedestrian. Research was conducted to find sensor technologies that can be used to passively detect pedestrians. Five technologies were found to be options for this type of detection: passive infrared, ultrasonic, microwave radar, video imaging, and piezometric. Of these five technologies, passive infrared, ultrasonic, and microwave radar were selected for testing. An unbiased selection of sensors was made by using a decision matrix in the form of the quality function deployment method, which also provides a record of sensor information for future research. Preliminary testing was conducted on the sensors to ensure that the detection of pedestrians was possible and to determine sensor operating characteristics. Sensors then went through secondary tests to ensure proper operation at an unsignalized crossing. The secondary test site was retrofitted with reflective pedestrian crossing signs, yellow beacons, Doppler radar, and passive infrared sensors chosen from the preliminary tests. Initial secondary tests have shown promising results for the Doppler radar and especially for the passive infrared sensors. Future applications of passive pedestrian detection in Portland will involve installation of sensors at signalized pedestrian crossings.
Ultraviolet Headlamp Technology for Nighttime Enhancement of Roadway Markings and Pedestrians
Authors: Turner Dan , Nitzburg Marsha , Knoblauch Richard
Published: April 2007

Motorists driving at night are two to three times more likely to be involved in a crash than during the day. Although, about half of the motor vehicle deaths occur at night, death rates based on miles driven are about four times higher at night than during the day. Nighttime driving also frustrates a large number of people, the majority of which are seniors. There is an effort under way to evaluate the use of supplemental ultraviolet (UV) automobile headlights to increase nighttime visibility. Research conducted in Sweden has shown very promising results, and a preliminary field research effort recently completed in the United States found that the visibility of pavement markings increased 25 percent with UV, and subjects generally favored its use. An extensive field study was conducted to determine the conditions under which driver performance could be improved with fluorescent traffic control devices and auxiliary UV headlights. Several static tests were done to evaluate fluorescent pavement markings, post-mounted delineators, and various pedestrian scenes under two headlight conditions (low beam only and low beam with UV). Dynamic tests included a subjective evaluation of two headlamp conditions and a performance test in which subjects drove an instrumented vehicle. The results of the field study indicated that pavement markings could be observed 30 percent further, and pedestrians could be observed over 90 percent further with the addition of UV. Subjects consistently evaluated the use of UV headlamps as beneficial.
Child Pedestrian–Car Crashes Near Schools Are a Small Percentage of Total Child Pedestrian Crashes in Philadelphia
Authors: Jordan Gihon
Published: April 2007

An analysis was conducted of 2,167 pedestrian-car crashes reported by the Philadelphia Police Department in 1994. Age, sex, location, type and severity of injury, and neighborhood of victim and driver were taken directly from the police reports. The pedestrian’s actions were coded into 43 categories using the description in the police report. The unique aspect of this research is that the distance to the nearest school was measured and included in the database. The impetus to create this database was a politician’s demand that School 15 mph flasher signs be installed at the over 500 schools in Philadelphia. Only three schools in Philadelphia had school flashers when these data were collected in 1994. Most schools had School Crossing signs and School 15 mph speed limit signs where appropriate. There were about 600 school crossing guards in 1994. The data indicate that few children are injured by cars near schools during opening, recess, and closing times. More children are injured en route to or from school, but not near the school. A greater number are injured while playing after returning home from school than are injured during the trip to or from school combined. Thus, an implementation of in-school child traffic safety education, installation of new strong yellow-green School Crossing signs, and targeted and advertised enforcement of motor vehicle laws would be better responses to child traffic safety than the wholesale installation of flashing school speed limit signs. The data also confirm that dart-outs, other nonintersection crossings, traffic signals, and playing in the street are the principal crash types for children. Philadelphia has a very high rate of unlicensed, unregistered, and uninsured drivers (estimated at over 40 percent). Enforcement is lax, and the traffic court dismisses most moving violation cases. Children deserve to be made safer 24 hours a day, 365 days a year. Flashers cannot do that because only a small percentage of crashes occur near schools during school hours and because flashers are ineffective in reducing speeds and car-pedestrian crashes near schools.
Use of Active Learning and Group Competition To Facilitate Training and Technology Transfer for Adult Learners
Authors: Zacharia Zach , Jennings Barton
Published: April 2007

Adult training is different from the more traditional training used in many of today’s public schools. Adults have more experiences on which to base their decisions and generally are more skeptical of education. There is a need for relevancy in the materials presented, and many negative impressions must be overcome. To address these and other issues, a number of techniques are now being applied to facilitate training and technology transfer for adult learners. A technology transfer program originally aimed at adults working for the Tennessee Department of Transportation (TDOT) was designed to educate workers about using metric units in the workplace. Because of the subject, the time constraints, and the generally negative reaction that participants in test courses demonstrated, the program was designed using several of the techniques now becoming popular in adult education. Besides the use of short lectures, these techniques included active learning and group competition, using games and exercises with token rewards for success. Nearly 4,000 individuals have attended the program in Tennessee and Kentucky. Participants have come not only from TDOT but from city and county governments, contractors and engineering firms, and suppliers. Participants’ job responsibilities have included everything from clerical to company president and owner. Follow-up surveys have revealed a strong positive response to the program and a belief that technology transfer via training is being accomplished successfully using this combination of training techniques.
Technology Transfer to the Caribbean Case Study of Kingston, Jamaica
Authors: Dawkins Janine , Daniel Janice
Published: April 2007

Technology transfer to developing countries has traditionally involved the transfer of tools and methodologies developed in industrialized nations for use in poorer developing countries. Good technology transfer, however, includes knowledge of the relationships between the fundamental principles involved in the design of the technology, rather than implementation of an existing finished product. For successful transfer of technology to developing countries to occur, it is important to recognize the differences between developing countries and industrialized nations because differences in social and economic conditions between the two types of countries may warrant alternative approaches both to analysis and to implementation of solutions. The transfer of transportation technology can be inappropriate where driver behavior is a significant factor, such as in the analysis of intersections controlled by stop signs. Observations of drivers at stop-controlled intersections in Kingston, Jamaica, show that drivers seem to be more interactive than those in the United States. For example, drivers on the major approach of a two-way stop-controlled intersection have been observed to yield their right-of-way to vehicles on the minor or stop-controlled approach. The objectives of this research are to assess the suitability of methodologies developed for use in the United States for evaluating stop-controlled intersections in Kingston and to propose an alternative methodology that may be more appropriate for Kingston and locales in other developing countries with similar driver and roadway characteristics.
Application of Microwave Energy for Indirect Determination of Asphalt Total Polarity and Sulfur and Sulfide Content
Authors: Bishara S. W. , Mahoney Donna
Published: April 2007

A simple, inexpensive, and rapid—yet accurate—method is presented for the indirect determination of relative total polarity and sulfur and sulfide content of asphalt. For a given asphalt, the three parameters can be calculated from one measurement on a scientific microwave instrument. Using the eight Strategic Highway Research Program core asphalts, the dielectric heating time required for 10-g asphalt to reach a target temperature of 150°C was measured: AAD-1 took 10 min, whereas AAM-1 took 111.5 min. Because of this wide time range covered by the eight asphalts, the dielectric heating time may serve as a characterization test. The dielectric heating time correlates perfectly, r2 = .998 or 1.00, with total polarity of the four core asphalts for which total polarity has previously been determined by others. The curve equation was then used to calculate total polarity of the other four core asphalts, and may be used for any given asphalt once its dielectric heating time to reach a target temperature is measured. For the seven core asphalts with a nickel to vanadium ratio (Ni/V) > 1, the dielectric heating time correlates perfectly ( r2 = 1.00) with the sulfur content previously determined by others. For AAG-1, ABM-1, and ABD-1 (all have Ni/V < 1), a separate equation applies, also with r2 = 1.00. Sulfide content, previously determined by others, for the seven core asphalts with Ni/V > 1 correlates perfectly ( r2 = 1.00) with dielectric heating time. No separate equation could be derived for asphalts with Ni/V < 1 because only sulfide content of AAG-1 was known. For a given asphalt, sulfur and sulfide content can be calculated from the corresponding equation once the dielectric heating time is measured. The proposed method has a reasonable repeatability and bias for the three determined parameters.
Asphalt Aging: Dual Oxidation Mechanism and Its Interrelationships with Asphalt Composition and Oxidative Age Hardening
Authors: Petersen J. Claine , Harnsberger P. Michael
Published: April 2007

The kinetic data and chemistry of asphalt oxidative age hardening suggested a sequential, dual mechanism for asphalt oxidation. The dual mechanism rationalizes conflicts between earlier mechanistic investigations and explains the hyperbolic-like, time-versus-property plots characteristic of asphalt oxidative aging. The oxidation kinetics provide further confirmation of the asphalt microstructural model. It is proposed that the rapid initial oxidation rate of asphalt results from reaction of oxygen with limited amounts of highly reactive hydrocarbons. Final oxidation products of this initial reaction are sulfoxides and, most likely, ring aromatization. During this initial reaction, a slower oxidation reaction of asphalt benzylic carbons is initiated; final products are ketones and sulfoxides. The ratio of ketones to sulfoxides formed and the rate of age hardening were found to be dependent on temperature and oxygen pressure. Low-temperature oxidative aging, as occurs in pavements, was found significantly more sensitive to variations in temperature and asphalt composition than 100°C pressure vessel aging.
Comparative Study of RTFOT and PAV Aging Simulation Laboratory Tests
Authors: Migliori Francis , Corté Jean-François
Published: April 2007

Tests were performed on unmodified asphalts of 35/50 grade penetration produced by French refineries to determine whether a prolonged pressure aging vessel (PAV) test would provide similar results to those obtained using the Strategic Highway Research Program coupled aging procedure, rolling thin film oven test (RTFOT) and PAV. Asphalts subjected only to PAV tests and identical samples after RTFOT and increasing PAV time were compared on the basis of ( a) conventional consistency tests, penetration at 25°C, ring and ball softening temperature; ( b) asphaltene content; ( c) creep rheological tests at low temperature with the bending beam rheometer; and ( d) complex modulus tests with the Metravib dynamic rheometer. The results show that a hypothesis of equivalence between the effects of ( a) RTFOT and 5 h of PAV aging at 100°C and under 2.1 MPa and ( b) RTFOT + 20 h of PAV and 25 h of PAV under the same conditions seems acceptable for the category of asphalts investigated.
Aggregate Toughness/Abrasion Resistance and Durability/Soundness Tests Related to Asphalt Concrete Performance in Pavements
Authors: Wu Yiping , Parker Frazier , Kandhal Prithvi S.
Published: April 2007

Numerous tests have been developed that empirically characterize aggregate without, necessarily, having a strong relationship to the performance of the final products incorporating these aggregates. This seems to be particularly true for aggregate toughness and abrasion resistance and durability and soundness. Toughness/abrasion resistance and durability/soundness tests for characterizing aggregate used in asphalt concrete were identified and evaluated, and those test methods that best correlate with field performance were determined. Based on a review of literature and specifications, laboratory tests for characterizing aggregate toughness/abrasion resistance and durability/soundness were selected. Sixteen aggregate sources with poor to good performance histories were identified for evaluation with the selected suite of tests. Performance histories of pavements containing these aggregates in asphalt concrete layers were established through personal contacts with state transportation agencies and performance evaluation questionnaires. Aggregate properties from laboratory tests were correlated with field performance. The micro-deval and magnesium sulfate soundness tests provide the best correlations with field performance of asphalt concrete and are recommended for characterizing aggregate toughness/abrasion resistance and durability/soundness.