bluuebunny/crossref_metadata_2025 huggingface dataset:
Elastic Pavement Analysis Using Infinite Elements
Authors: Hjelmstad Keith D. , Zuo Qiuhai , Kim Jiwon
Published: April 2007

A numerical analysis of a multilayered rigid pavement system is presented. To efficiently model the behavior of the subgrade soil layers in the horizontal direction, infinite elements are used to represent the decaying feature of the field variables (displacements and stresses) in the far field. Ordinary finite elements are used in a relatively small region around the applied loads to accurately capture the stress field. Compared with a conventional finite-element analysis of pavements, wherein a finite size of the computational domain must be chosen and artificial boundary conditions must be assumed at the truncated boundary, the current approach can significantly reduce the total number of elements, saving considerable computation time and thereby making feasible more extensive analysis.
Productivity Frequency Index
Authors: Warren Kenneth J.
Published: April 2007

The frequency of bus service on a specific route is directly related to the number of passengers using the route. Routes that exhibit high ridership should be provided frequent service, whereas routes with low ridership should be provided less frequent service. The productivity frequency index used by the Milwaukee County Transit System quantitatively measures the relationships between ridership demand and the frequency of service for each bus route both by route segment and by time of day. Use of this measure assists the transit system in equitably allocating the supply of transit service between individual routes, thereby resulting in more effective and efficient operations.
Blaming the Victors: Characteristics of Public Transit Vehicle Operators Involved in On-Board Altercations
Authors: Hundenski R. J.
Published: April 2007

The characteristics of public transit vehicle operators reporting problematic encounters with passengers or other persons were examined. While some association was found between involvement in such encounters and female gender, the major finding was that nearly half of all reported incidents over a 5-year period involved operators reporting more than one such incident. Moreover, that population was overrepresented by male operators, with operators reporting three or more such incidents being almost exclusively male. These operators also tended to be from a particular ethnic group. That finding led to a change from the original perspective, in which drivers were viewed as hapless victims of predatory persons, to one in which the interactional style of operators was seen as a contributory factor in the occurrence, progress, and outcome of problematic encounters. It was concluded that conflict arising from the problematic encounters is essentially about status: its assertion, affirmation, or maintenance. So strong is the drive to preserve status that considerable risks will be taken. A description of the structure of social interaction is provided, and organizational responses are discussed.
Application of Industrial Standards to Bus Maintenance Procedures
Authors: Paaswell Robert E. , Audenaerd Laurence , Jafari Mohsen
Published: April 2007

To increase productivity and achieve promised operating budget savings, the Metropolitan Transportation Authority of New York City wished to optimize bus maintenance routines throughout its different divisions. New York City Transit and the Manhattan and Bronx Surface Transit Operating Authority entered an agreement with the Local 100, Transport Workers Union of America of Greater New York, AFL-CIO to form a team of delegates, under the supervision of a mediating industrial engineer (IE), to create standard task times for 26 specified bus maintenance core procedures. Within 90 days, this process intended to ( a) create fixed standards for each task, and ( b) reduce times now spent on certain jobs. Throughout the process, labor and management were urged to articulate rationales and listen to explanations. Predictable arguments were initially cited, but these evolved into discussions of new approaches or considerations agreeable to both sides. In a disagreement, the IE tried to narrow differences and facilitate agreement on an intermediary value determined by timed demonstrations. The method invoked an iterative process of negotiation, converging upon the final agreement, which proved to be an interesting heuristic in general for similar mediation processes. This process of union and management coming together on issues of productivity is certainly not new and has been studied in the past. But, at a time when all transit budgets are under fire, issues such as saving jobs while reducing costs assume great importance.
Integration of Paratransit and Transit Services: Importance of Vehicle Transfer Requirements to Consumers
Authors: Balog John N. , Morrison John B. , Hood Mark M.
Published: April 2007

The integration of paratransit and transit services is necessary in order to fully achieve the requirements of the Americans with Disabilities Act. Many individuals with disabilities can use accessible fixed-route vehicles but do not because they are unable to get from their origin to an accessible bus stop. Using paratransit as a feeder service to the fixed-route system can minimize the total cost to the transit system of providing services to this segment of the population. It must be understood, however, that transferring patrons from one vehicle to another is undesirable to consumers. This is documented by the results of three studies covering a variety of locations across the United States. The surveys showed that a number of market categories of consumers ranked no transfers between vehicles as the No. 1 service feature that was necessary to attract them to the fixed-route system. Of 16 market categories, all determined no transfers to possess a positive utility for attracting them to fixed-route services. To satisfy consumer needs and to minimize costs to transit authorities, the negative characteristics of vehicle transfers must be mitigated through design. This can be done by providing timed transfers at designated points so that wait time is eliminated or minimized. Such transfer points must also be protected from the difficulties of poor weather conditions and must be well-lighted and secure. The provision of aids to assist in the transfer may also be necessary.
Development of Proposed Myrtle-Wyckoff Intermodal Facility
Authors: Perales Patricia
Published: April 2007

The Myrtle-Wyckoff Intermodal Facility proposal is presented, its planning process is discussed, and recommendations for future partnerships between New York City Transit (NYCT) and the New York City Department of Transportation (NYCDOT) are given. The planning of this intermodal project was affected by three factors: the planning is a joint effort of two public organizations, it is being formulated for a transportation system that has few intermodal facilities, and it is being developed during austere capital budget cuts. The partnership developed because the intermodal facility will be partially financed with federal Congestion Mitigation Air Quality (CMAQ) funds. NYCDOT was awarded the CMAQ funds, and NYCT will own and operate the facility. Second, because NYCT was conceptualized in the 19th century by private companies, the transportation systems are not integrated because of the physical infrastructure and unparallel service plans. In the past decade, NYCT has taken a variety of initiatives to coordinate and integrate the services. Creation of intermodal facilities is one of the goals of the NYCT 1995–1999 Strategic Business Plan. The project is a good capital investment. However, organizational priorities and funding constraints prevented it from being included in the proposed capital program. Capital projects evolve in four phases: concept consideration, adoption of concept, implementation, and operation. The development of the project from the consideration phase to the adoption phase is presented. The conclusion will list recommendations for future planning partnerships between NYCT and NYCDOT.
PART 6: Light Rail Transit: We Can’t Hear You! San Diego’s Techniques for Getting Balanced Community Input in Major Investment Studies
Authors: Bates Toni Botte , Wahl Dennis J.
Published: April 2007

Virtually all public works projects require a substantial planning effort to identify impacts, costs, and alternatives. Federal and state laws and regulations call for certain levels of public involvement during planning, but meaningful, collaborative public involvement entails doing more than the minimum requirements. This is particularly true when there appears to be an imbalance in public input, where one viewpoint is heard above others. The San Diego Metropolitan Transit Development Board (MTDB) has undertaken efforts on two corridor projects to expand its public involvement in ways that maximize the range of community views, enhance project design, and build support for the project. In addition to the traditional public meetings, newsletters, and open houses, MTDB has used public relations firms, neutral facilitators, and staff outreach to achieve expanded public involvement goals. MTDB has found that, while there are risks and costs associated with these approaches, they ultimately result in better projects that receive more widespread public and political acceptance.
Comparative Analysis of FRESIM and 1994 Highway Capacity Manual Models for Ramp Junctions with an Independent Data Base
Authors: Ulerio Jose M. , Roess Roger P. , Lee John W.
Published: April 2007

The results of a comparative analysis of the 1994 Highway Capacity Manual (94HCM) ramp junction models and the FRESIM simulator model with an independent data base are described. The analysis was done as part of NCHRP Project 3-37 (Phase II), whose objective was to identify and investigate common ranges of application, consistency of internal logic, consistency of results, and potential modification to both the 94HCM and the FRESIM models. The results indicate that FRESIM may be a reasonable tool for predicting operational parameters within the area of ramp junctions for isolated ramps, although they also indicate that FRESIM may not be sensitive enough to some geometric parameters to be used confidently in its current form.
Capacity of Roundabouts in Jordan
Authors: Al-Masaeid Hashem R. , Faddah Mohammad Z.
Published: April 2007

An empirical model for estimating roundabout entry capacity for conditions in Jordan has been developed. The performance of the model was compared with the performance of capacity models in Europe. Data, collected from different cities in Jordan, consisted of 775 min of at-capacity operation and included both roundabout traffic and geometric variables. The analysis indicated that circulating traffic flow, widths of entry and circulating roadway, central island diameter, and distance between an entry and a near-side exit had a significant influence on entry capacity. Compared with German, Danish, and French roundabout models, the Jordanian capacity model provided comparable estimates, especially with low levels of circulating traffic.
Unsignalized Intersection Analysis: Effect of Overlapping Conflicting Traffic Flow on Minor Movement Potential Capacity
Authors: Fasching Christopher J.
Published: April 2007

A particular component of two-way stop unsignalized intersection analyses as presented in the 1994 Highway Capacity Manual (HCM) is described. Specifically, advantages to minor movement capacity are evaluated where traffic flows overlap in multiple lanes. From vehicular arrival data collected by the author, it was determined that the current HCM can significantly underestimate the true potential capacity of minor movements that face multiple lanes of free-flow conflicting traffic. A modification to the HCM procedure is introduced in which an “effective” conflicting flow is calculated on the basis of “blockage” caused by individual lanes of traffic, assuming a Poisson count distribution. In every case examined (24 total), a more accurate potential capacity estimate resulted relative to that determined by the HCM procedure. The modification also resulted in a more accurate level of service in 8 of the 24 cases.
Effect of Upstream Signal on Nonpriority Movement Capacity and Delay
Authors: Bonneson James A. , Fitts Joel W.
Published: April 2007

A methodology is described for estimating the capacity of and the delay to nonpriority movements at a two-way stop-controlled (TWSC) intersection in the presence of an upstream signalized intersection. The methodology is centered around the capacity of and the delay to the major-street left-turn movement; however, it is also directly applicable to the minor-street right-turn movement. With some adjustment, the methodology can also be applied to minor-street left and through movements. The findings indicate that upstream signals have a significant effect on the capacity and delay of nonpriority movements at TWSC intersections. Specifically, the traffic platoons formed by the signals tend to increase capacity and decrease delay. The magnitude of the effect of the upstream signal is dependent on the amount of platoon dispersion that takes place as the platoon travels down the street. Several factors affect the rate of platoon dispersion, including travel distance, level of driveway activity, and the arterial cross section. A rationale is presented for inclusion of a minimum, nonzero capacity for nonpriority movements. This minimum capacity approximately accounts for behavior of drivers confronted with lengthy delays and in the presence of platooned traffic flows. The minimum capacity value providing the best fit to the simulation data was 165 vehicles per hour.
Electromagnetic Properties of Concrete and Their Significance in Nondestructive Testing
Authors: Buyukozturk Oral
Published: April 2007

Electromagnetic properties of hardened concrete specimens are measured over a microwave frequency range from 0.1 to 20 GHz. The experimentally obtained values provide information about the behavior of concrete and its interaction with electromagnetic waves. In addition to the frequency variation, the effect of different moisture contents on the electromagnetic properties is studied. Properties of mortar specimens and constituents of concrete, that is, coarse aggregates, sand, and cement, are also measured. An open-ended coaxial probe method is used for the measurement of real and imaginary parts of complex permittivity of concrete. The physical significance of the measured data in nondestructive testing, including penetration depth and detectability, is discussed. The results of electromagnetic property measurements indicate that the dielectric constant of dry concrete appears to be frequency independent over the range from 0.1 to 20 GHz, whereas the loss factor increases over that range. The moisture content of concrete significantly affects the dielectric constant and loss factor. The quantitative results obtained from this research will serve as a basis in applying wideband microwave imaging techniques for nondestructive testing of concrete using radar. The results can also be used for selecting the optimum combinations of radar measurement parameters for better detection.
Freeze-Thaw Durability of Concrete with Ground Waste Tire Rubber
Authors: Savas Banu Zeynep , Ahmad Shuaib , Fedroff David
Published: April 2007

Used tires represent an increasingly serious environmental problem in the United States. This study examines the freeze-thaw durability of concrete with ground waste tire rubber. Various percentages of rubber, by weight of cement, were added to a control concrete mixture. To evaluate the freeze-thaw durability of these “rubcrete” mixtures, freeze-thaw tests in accordance with ASTM C666 Procedure A and microscopic analyses in accordance with ASTM C457 Procedure B, were conducted. Results show that the rubcrete mixtures with 10 and 15 percent rubber by weight of cement are freeze-thaw durable. Results of the microscopic analysis indicate that properties such as air content and spacing factors are difficult to determine accurately because of the problems associated with polishing of the rubcrete specimens.
Development of Performance-Related Specifications for Hot-Mix Asphalt Pavements Through WesTrack
Authors: Seeds Stephen B. , Basavaraju Rudramunniyappa , Epps Jon A. , Weed Richard M.
Published: April 2007

The primary objective of the FHWA-sponsored WesTrack project is to further the development of performance-related specifications for hotmix asphalt construction. This objective is being achieved, in part, through the accelerated loading of a full-scale test track facility in northern Nevada. Twenty-six hot-mix asphalt test sections constructed to meet the criteria set forth in a statistically based experiment design are providing performance data that will be used to improve existing (or develop new) pavement performance prediction relationships that better account for the effects that “off-target” values of asphalt content, air-void content, and aggregate gradation have on such distress factors as fatigue cracking, permanent deformation, roughness, raveling, and tirepavement friction. The concept of the planned new performance-related specification and how it will incorporate the modified pavement performance prediction models are described. The current plan for assessing contractor pay adjustments (i.e., penalties and bonuses) based on data collected from the as-constructed pavement is also discussed.
Extent to Which User Fees Cover Road Expenditures in the United States
Authors: Morris Hugh , Decicco John
Published: April 2007

The extent to which road users pay, through user fees, the full cost of the infrastructure and services they consume has been an issue for several decades. In contrast to most previous studies, a recent American Petroleum Institute (API) report concludes that payments by road users exceed direct government road expenditures by 50 percent. The API study points out that conventional accounts of road finance data report only revenues used for highways, thereby excluding funds from other automobile-related transactions (such as vehicle sales taxes) that are not specifically spent on roads. Two major issues with the accounting methodology used by API are identified: incorrect attribution of general taxes as user fees and neglect of various road-related costs. Combined, these shortcomings inflate the revenue side of the ledger and hold down the expenditure side. A more detailed accounting of the revenues generated by road users as well as the public costs, both direct and indirect, that are attributable to the road system and its use is presented. Reexamination of the 1992 accounts indicates that total public expenditures on road-related items were $97.2 billion, whereas public revenues specifically raised from road users amounted to $75.5 billion. The result is a gap of $21.7 billion that was spent on road-related items that were not covered by road user fees. Thus, road user fees covered only 78 percent of public road-related costs in the United States in 1992.
Transport Demand Management by Electronic Fee Collection in a Zone-Based Pricing Scheme: The Stuttgart MobilPASS Field Trial
Authors: Hug Klaus , Mock-Hecker Rüdiger , Würtenberger Julian
Published: April 2007

All attempts to reduce traffic and to change the modal split in favor of public transportation have failed to slow the increase of private transportation in urban areas in recent years. Therefore, urban traffic has become a major problem in many countries. One promising approach to the control of traffic demand in an efficient way is to introduce variable demand-based pricing schemes in urban areas. However, there have been few systematic field trials on the effect of road user charges on travel behavior. The MobilPASS field trial in Stuttgart, Germany, has now investigated the effect of variable road pricing charges on road users’ behavior at a level of detail that is unique. Special attention was paid to the interaction between the charging schemes and reductions in the number of trips, changes of mode of transport, route changes, and time shifts. The empirical results presented indicate that time- and route-dependent road charges have the desired results.
Incentive Tolls for Congestion Management: A Planning Tool for the Port Authority of New York and New Jersey
Authors: Doxsey Lawrence B.
Published: April 2007

A congestion pricing planning model was developed for the Port Authority of New York and New Jersey. The model is designed to evaluate possible incentive tolls for their effects on congestion delays at the six bridges and tunnels the authority operates between New Jersey and New York. The study used a stated preference survey administered to bridge and tunnel users, econometric choice models, and plaza volume-delay relationships as a basis for simulating the effects of changes in toll structure. The survey identified characteristics of trips, feasible alternatives for the trips, and the trip makers. A stated preference choice exercise was included to reveal trade-offs among toll, plaza delay, facility choice, and time period when the crossing would be made. Responses to the exercise were combined with other survey data, and econometric models of choice were estimated. The models associate the probability of travel choices with the conditions faced at the alternatives. The policy evaluation planning model combined choice model results, survey responses from individual respondents, and data on facility conditions, volumes, and capacities. As input it accepts a user-specified menu of tolls and discounts, potentially varying both by hour and by facility. As output it predicts automobile volumes, average delays, total delays, and toll revenue by hour and facility. The model is constructed to achieve equilibrium among tolls, delays, and volumes. Application of the model indicates considerable potential for reducing plaza delays.
Buying Time: Institutional and Political Issues in Congestion Relief Tolls
Authors: Munnich Lee W. , Van Hattum David , Zimmerman Maria V.
Published: April 2007

Congestion relief tolling refers to charging drivers a fee that varies with level of traffic (or demand) on a congested tollway. The recent implementation and study of congestion relief tolls in this country are described. Findings are based on focus groups, telephone and personal interviews, a Citizens Jury, and three regional conferences held in conjunction with the Federal Highway Administration. The economic rationale for congestion relief tolls and the key reasons why they are being considered by transportation planners and policy makers are outlined. Seven recommendations that address the political and institutional issues associated with building support for implementation are made.
Exclusive Lanes for Trucks and Cars on Interstate Highways
Authors: Vidunas Joseph E. , Hoel Lester A.
Published: April 2007

Increases in heavy truck traffic on the nation’s highways in recent years have raised concerns about safety and capacity, particularly on the Interstate system. In response, a number of strategies for dealing with the effect of truck traffic on safety and capacity have been developed. One promising strategy is to provide separate lanes for trucks and cars on freeways or Interstates. However, since separate lane strategies have not been widely used, little is known about their economic and operational effects. An FHWA computer model, referred to as EVFS, was evaluated. The model determines the economic feasibility of separating trucks and other vehicles on freeway segments. Practices and experiences with exclusive facilities nationwide were examined. EVFS can analyze many alternatives for a variety of conditions. It is inexpensive and easy to use. However, EVFS does not differentiate between the lanes to which exclusions are applied (inside, middle, outside), and physical barriers are not treated explicitly. To demonstrate the application of the program, 10 lane separation strategies were evaluated for a 50.7-km (31.5-mi) segment of I-81 in Virginia. The results of the I-81 analysis indicate that user savings can be achieved if one or more lanes are designated for the exclusive use of trucks or cars.
Social Cost Component of an Efficient Toll
Authors: Tellis Raymond , Khisty C.
Published: April 2007

Efficient tolls are tolls that ensure that the price paid by the roadway user is equal to the increment of social and private costs resulting from the highway use. Setting these tolls accomplishes an important objective: to correct the current practice that allows driving to be subsidized by government and nonusers. Without restrictions on vehicle ownership and unlimited access to the nation’s cost-free roadways, drivers do not pay for the social costs they generate. If motorists were required to pay their fair share of these social costs, travel decisions would probably be altered. Unwarranted trips, especially during peak hours, would be reduced because roadway space would be priced to accurately reflect the actual cost of driving. Beyond private costs, society is burdened with paying for infrastructure construction and maintenance, highway services, wasted fuel, pollution, accidents, and congestion costs from travel delays. The cost to society of automobile travel is assessed so that a charge can be made for the social cost component in computing what an efficient toll should be. It is found that the social cost fee during nonpeak travel comes to 0.67¢/vehicle-km (1.08¢/vehicle-mi). Travel during peak periods is far more expensive with the addition of congestion costs. The value of time drives up these costs, and the charges amount to 5.68¢/vehicle-km (9.14¢/vehicle-mi) for peak-period travel.
Kansas Experience with Strategic Highway Research Program Washington Hydraulic Fracture Index Test
Authors: Zubery Muhammad H. , Hossain Mustaque , Clowers Karen C.
Published: April 2007

D-cracking due to frost-susceptible coarse aggregates has been a problem on Kansas pavements since the 1930s. However, a reliable, reproducible, easily performed, and inexpensive test method for rapidly assessing the freeze-thaw durability of aggregates is yet to be developed. A method was developed in the Strategic Highway Research Program (SHRP)—the Washington hydraulic fracture index (WHFI) test—apparently capable of identifying nondurable aggregates in about 8 days. Thirty-two limestone aggregates from Kansas sources were tested according to the WHFI procedure. A comparison of existing Kansas criteria for durable aggregates and the percentage fracture values obtained in the WHFI tests indicates that if 5 percent or more fracture percentage is used as the failure criterion, then 14 out of 32 aggregates (44 percent) are identified correctly with respect to the durability criterion. For 3 percent or more fracture percentage, 18 out of 32 aggregates (56 percent) are identified correctly. A correlation study shows that the WHFI test results are correlated significantly with the results of the freeze-thaw tests of the Kansas Department of Transportation on unconfined aggregates. However, the WHFI test results are poorly correlated with the results of ASTM C666 tests on concrete prism specimens of these aggregates. Since ASTM C666 is universally accepted to predict the frost-susceptibility of aggregates in concrete, the SHRP WHFI test method, in its current form, does not appear to be a viable choice to replace it. However, if the WHFI test can be modified to test concrete prisms, better correlations with ASTM C666 results can be expected.
Geotechnical and Environmental Characteristics of Atmospheric Fluidized Bed Combustion Ash and Stoker Ash
Authors: Deschamps Richard J.
Published: April 2007

Results of geotechnical and environmental laboratory tests on atmospheric fluidized bed combustion ash and stoker ash are presented. The testing program is directed toward assessing the adequacy of using these materials as structural fill in roadway embankment construction. Geotechnical tests include specific gravity, standard Proctor compaction, permeability, California bearing ratio, strength, and swell tests. Environmental tests include bulk chemical analysis of major and trace elements, toxicity characteristic leachate procedure, extraction procedure toxicity, and Indiana neutral water leachate tests. The fluidized bed combustion ash and mixtures with stoker ash exhibit significant cementitious strength increase, and swelling with time. The implications of test results relative to use as structural fill are discussed.
Using Auditory Pedestrian Signals To Reduce Pedestrian and Vehicle Conflicts
Authors: Van Houten Ron , Louis Malenfant J. E. , Van Houten Joy , Retting Richard A.
Published: April 2007

Turning vehicles are a potential threat to pedestrians at intersections. As a possible countermeasure, an experimental auditory pedestrian signal was developed to prompt pedestrians to look for turning vehicles at the start of the walk signal. Analysis of observational data collected during the experiment shows that the auditory signal increased pedestrian-observing behavior and almost eliminated pedestrian motor vehicle conflicts at a signalized intersection. The presence of the auditory message appeared to prime pedestrians to respond more rapidly to turning vehicles.
Integrated Systems Methodology for Pedestrian Traffic Flow Analysis
Authors: Romer Richard T. , Sathisan Shashi K.
Published: April 2007

A typical urban pedestrian transportation system involves three basic elements: sidewalks or walkways; midblock or intersection corner, holding, or queuing areas; and pedestrian crossings of roads, railway lines, or other physical features of the transportation network. The pedestrians on sidewalks or walkways have operating characteristics analogous to motorized vehicles on roadways. The level of service and capacity analyses of sidewalks have been documented in the literature. In a similar manner, the concept of capacity and level of service have been individually applied to the street corner area and the crosswalk. Each critical pedestrian element has been considered individually, but not as a balanced system, especially at the most critical link—the signalized urban intersection. A methodology and guidelines are presented to analyze existing pedestrian elements at a signalized intersection, that is, the sidewalk, intersection corner, and crosswalk, with a systems approach that identifies key interrelationships of the individual elements. This systems approach can guide the design of a balanced at-grade pedestrian transportation system. It can be used to evaluate existing signalized at-grade intersection pedestrian elements, and to develop decision support tools to evaluate the potential need for a grade-separated pedestrian facility.
Sketch-Plan Method for Estimating Pedestrian Traffic for Central Business Districts and Suburban Growth Corridors
Authors: Ercolano James M. , Olson Jeffrey S. , Spring Douglas M.
Published: April 2007

There is a growing need for quantitative traffic-estimating tools to improve pedestrian transportation safety, access, and mobility. A sketch-plan method is introduced to estimate peak-hour pedestrian trips for crossings at intersections (node) and parallel sidewalk-midblock (link) locations. This tool integrates pedestrian travel into routine trip-estimating by applying standard traffic data to quantify pedestrian trips. The method presented is based on access-egress mode trip generation and applies peak vehicle-per-hour turning movements, transit vehicle or passenger counts, and walk and bike counts or projections to produce total peak pedestrian-per-hour (pph) trips. A previous method used trip rates based on land use to generate pph trips. However, that model is 20 years old, requires detailed land use data, and does not distribute and assign pedestrian trips. The following sketch-plan method was developed in a case-study of a suburban growth corridor in Plattsburgh, New York. Sample applications of pedestrian trip-generation estimates are presented to illustrate how pedestrian travel-demand projections, in addition to vehicular traffic forecasting, can support the adoption of balanced facility treatments to meet the mobility and safety needs of all modes of transportation.
Effects of Site Design on Pedestrian Travel in Mixed-Use, Medium-Density Environments
Authors: Moudon Anne Vernez , Hess Paul M. , Snyder Mary Catherine , Stanilov Kiril
Published: April 2007

Whether high or low incidence of pedestrian travel in mixed-use, medium-density environments is due to site design characteristics, and specifically to presence of direct, continuous, and safe pedestrian systems, is examined. Twelve neighborhood centers or sites in the Puget Sound area of Washington were selected by matching gross residential density, median income, automobile ownership, and intensity and type of neighborhood commercial development. Pedestrians and bicyclists were recorded that traveled into the commercial area. A clear break emerges between urban and suburban sites. The average urban pedestrian volume is 37.7 pedestrians per hour per 1,000 residents, which is 3 times higher than the 12.5 pedestrians per hour per 1,000 residents in suburban sites. These results strongly support the hypothesis that, when holding other variables constant, the urban versus suburban difference in route directness and completeness of pedestrian facilities (namely, block size and sidewalk length) affects pedestrian volumes. The research also questions the common belief that people do not walk in the suburbs. Given appropriate land use conditions, pedestrian facility improvement programs in suburban areas can support pedestrian travel and have a significant influence on mode choice.
Influence of Environmental Design on Pedestrian Travel Behavior in Four Austin Neighborhoods
Authors: Shriver Katherine
Published: April 2007

Results of a pedestrian survey conducted in two pairs of Austin, Texas, neighborhoods that possess either pedestrian-oriented or automobile-oriented transportation system, land use, and design characteristics but similar density, housing, and sociodemographic characteristics are reported. Survey results identify the influence of contrasting neighborhood forms on structural characteristics of walk-activity patterns and attitudes as mediated by personal characteristics. Walk-activity patterns significantly vary between neighborhoods with different accessibility characteristics. In the physically accessible neighborhoods, walks are predominantly short and frequent utilitarian trips that involve more secondary activities. Activity in the less accessible neighborhoods is characterized by longer, less frequent recreational walks that involve fewer secondary activities. Results support the conclusion that neighborhood transportation, land use, and design characteristics influence walk distance, duration, purpose, and number of secondary activities. The importance of walking in general and for specific purposes also varies with the relative levels of environmental variables. In the traditional neighborhoods, walkable distances, access to transit, shops, and work are more important, as is the opportunity to be outdoors. In the modern neighborhoods, walkway continuity, trees, and interesting things to look at are more important environmental attributes, as is the opportunity to maintain health. Accessibility affects walk activities as well as associated attitudes, but it is mediated through personal factors such as number of household cars, number of children, and household size. Evidence that pedestrians more highly value the available opportunities for walking suggests that latent predilections towards walking shape residential preferences.
Evaluation of Shared-Use Facilities for Bicycles and Motor Vehicles
Authors: Harkey David L. , Stewart J. Richard
Published: April 2007

This study was conducted for the Florida Department of Transportation with an objective of evaluating the safety and utility of shared-use facilities to provide engineers and planners comprehensive results that can be used in planning, designing, and constructing roadways to be shared by motorists and bicyclists. The results were developed from an analysis of observations of bicyclists and motorists interacting on different types of roadways. The evaluation included roadways with wide curb lanes, bicycle lanes, and paved shoulders. Locations from both rural and urban environments were included and varied in terms of motor-vehicle speed, traffic volume, lane width, and number of lanes. The operational measures of effectiveness used in evaluating the different types of facilities included ( a) lateral placement of the bicyclist, ( b) lateral placement of the motor vehicle, ( c) separation distance between the bicycle and the motor vehicle, and ( d) encroachments by the motorist or bicyclist during the passing maneuver. Results of the analysis showed that the type of facility (wide curb lane versus bicycle lane versus paved shoulder) does have a significant effect on the separation distance between bicyclists and motor vehicles; this distance ranged from 1.80 to 1.95 m (5.9 to 6.4 ft). The findings also indicated that paved shoulders and bicycle lanes generally result in similar interactions between motorists and bicyclists and that when compared with wide curb lanes they offer some distinct advantages to both user groups. The results also indicated that bicycle lanes as narrow as 0.92 m (3 ft) provide sufficient space for motorists and bicyclists to interact safely. At the same time, a 1.22-m (4-ft) wide bicycle lane tended to optimize operating conditions because there were very few differences in the measures of effectiveness when 1.22-m lanes were compared with wider lanes.
Real-Time Human Perceptions: Toward a Bicycle Level of Service
Authors: Landis Bruce W. , Vattikuti Venkat R. , Brannick Michael T.
Published: April 2007

The primary focus of this study by Sprinkle Consulting Engineers, Inc. is to develop a bicycle-quality, or level-of-service, model for applications in U.S. metropolitan areas. Although there are several model forms being used throughout the United States that attempt to quantify road suitability or the quality of service afforded bicyclists traveling the street and roadway networks of urbanized areas, to date there have been no statistically calibrated models published. The statistically calibrated level-of-service model described here is based on real-time perceptions from bicyclists traveling in actual urban traffic and roadway conditions. The study’s participants represented a cross section of age, gender, experience level, and geographic origin of the population of cyclists that use the metropolitan road networks in the United States. The test course is representative of the collector and arterial street systems of North American urban areas. Although further hypothesis testing is being conducted and additional studies are planned to test the need for disaggregate models for central business district streets with high turnover parking, truck routes, and two-lane high-speed rural highways, the general bicycle level-of-service model reported here is highly reliable, has a high correlation coefficient ( R2 = 0.73), and is transferable to the vast majority of United States metropolitan areas. The study reveals that pavement-surface conditions and striping of bicycle lanes are important factors in the quality of service.
Modeling Headlight Sight Distance on Three-Dimensional Highway Alignments
Authors: Hassan Yasser , Easa Said M. , Abd El Halim A. O.
Published: April 2007

Sight distance is one of the major elements that must be considered in the geometric design to achieve safe and comfortable highways. Daytime sight distance has been extensively studied, and analytical models for two-dimensional (2-D) and three-dimensional (3-D) alignments have been developed. However, nighttime (headlight) sight distance has received less attention. Despite the higher accident rate during nighttime than during daytime, existing analytical models evaluating headlight sight distance are very primitive. Moreover, the interaction between the horizontal and vertical alignments has not been modeled. A four-phase analytical model for headlight sight distance on 3-D combined alignments is presented. The model is an application of the finite-element technique in highway geometric design. The model can determine the maximum distance that can be covered by the vehicle’s headlights and that is not obstructed by any sight obstructions including the road surface. On the basis of this analytical model, computer software was developed and used in a preliminary application for 3-D headlight sight distances on a sag or crest vertical curve combined with a horizontal curve. The application showed that the 3-D sight distance on sag vertical curves was generally lower than the corresponding 2-D value when the sag curve was overlapping with a horizontal curve. On the other hand, the overlapping of horizontal curves with crest vertical curves enhanced the 3-D sight distance. The difference between 2-D and 3-D sight distance values in both cases increased with a decrease in the horizontal curve radius and an increase in the pavement cross slope. The model was proved to be extremely valuable in establishing 3-D highway geometric design standards.
Sampling Designs and Estimators for Monitoring Vehicle Characteristics Under Limited Inspection Capacity
Authors: Kinateder J. G. , McMillan N. J. , Orban J. E. , Skarpness B. O. , Wells D.
Published: April 2007

Estimating characteristics of motor vehicles and their occupants based on sampling a small portion of vehicles on the road is inherently a statistical problem. The problem has two components: construction of an efficient sampling design and application of an appropriate estimator to collected data. Constructing the sampling design should involve optimal utilization of limited resources to maximize information collected. The selected estimator should provide the most precise and accurate estimate of the characteristic of interest. Four sampling designs and two estimators for determining the proportion of vehicles with a particular characteristic are compared. A simulation example comparing these designs and estimators is provided. The illustration is based on a hypothetical road network typical of the primary transportation system in a metropolitan area of 500,000 to 1 million persons. Some suggestions for choosing appropriate sampling designs and estimators for other vehicle categorization problems are provided.
Testing for Instrumentation in Transportation Time Series Data: A Case Study
Authors: Rock Steven M.
Published: April 2007

Instrumentation is one of the threats to the validity of experiments. Four possible cases of instrumentation in a time series of traffic accident statistics in Illinois since the mid-1970s were tested, primarily by using autoregressive integrated moving average methods. Two of these cases, a 1977 change in the reporting threshold for property-damage-only (PDO) accidents and a 1989 change in the definition of a fatality, were not found to be significant. A 1989 change in the method of tabulating monthly data and a 1992 change in the reporting threshold for PDO accidents were statistically significant. These two cases combined could account for a more than 15 percent decline in PDO accidents.
Georgia’s Experience With Crumb Rubber in Hot-Mix Asphalt
Authors: Brown Dan R. , Jared David , Jones Chris , Watson Don
Published: April 2007

In 1991, the Georgia Department of Transportation (GDOT) began to evaluate the production and placement of crumb rubber hot-mix asphalt. The crumb rubber mix (CRM) used by GDOT was produced by adding ground tire rubber to hot-mix asphalt using the wet process. A test section of CRM was placed on I-75 in Henry County, just south of Atlanta, consisting of a surface mix containing 6 percent crumb rubber by weight of asphalt cement (AC). The test section was evaluated from 1991 to 1995. The test section indicated that the CRM became very brittle over time, as indicated by a large increase in viscosity and decrease in penetration, and by a large amount of transverse reflective cracking. Compared with the control mix, the CRM did not reduce rutting and was more than twice as expensive to place. In addition to the test section, two contract projects were initiated using CRM. These two projects indicated that CRM could be produced and placed using conventional equipment requiring only a few modifications. On-site blending units were used to combine the crumb rubber at a dosage rate of 16 percent by weight of AC. Pump and metering equipment was modified to accurately meter the stiff asphalt material, and correction factors were established for determining the AC content by vacuum extraction, since some of the rubber particles were retained in the aggregate portion of the sample.
Performance of Rubberized Asphalt Mixes in Alaska
Authors: Saboundjian Stephan , Raad Lutfi
Published: April 2007

A study was conducted to compare the fatigue, thermal cracking, and permanent deformation resistance of several Alaskan crumb rubber–modified (CRM) asphalt mixtures with that of conventional mixes. Alaska Department of Transportation and Public Facilities–designated sites in Fairbanks and Anchorage were sampled to conduct flexural beam fatigue tests, thermal stress restrained specimen tests (TSRSTs) and Georgia loaded wheel tests (GLWTs) on both rubberized and conventional mixes. Condition surveys were also conducted at the sampled sites to assess the field performance of these mixes in terms of fatigue, rutting, and low-temperature cracking. Fatigue testing results combined with multilayer elastic analyses for typical Alaskan conditions indicated an enhanced fatigue resistance for the CRM mixes when compared with conventional mixes. However, field performance observations at both conventional and CRM sections indicated no signs of fatigue distress, suggesting similar field performance for both types of mixes. TSRST results indicated an improved thermal cracking resistance for the CRM mixes, especially when the wet process was used. These results were consistent with observed field thermal cracking performance. At a given site, the section with the largest transverse crack spacing had the mix with the coldest TSRST fracture temperature. Conventional mixes outperformed CRM mixes in resisting permanent deformation, in both the lab and the field. GLWT results indicated that CRM mixes deform more and at a faster rate than conventional mixes. This may be due to the dense-graded aggregate used in some of the highly modified CRM mixes, where aggregate-to-aggregate contact and interlock were absent.
Structural Layer Coefficients of Crumb Rubber–Modified Asphalt Concrete Mixtures
Authors: Hossain Mustaque , Habib Affan , Latorella Todd M.
Published: April 2007

Structural layer coefficients for crumb rubber–modified (CRM) asphalt concrete mixtures were developed from the backcalculated moduli values using the falling weight deflectometer (FWD) test results on in situ pavements. Several test sections of recently built crumb rubber–modified pavements on three routes in Kansas (I-135, K-32 and US-56) were selected for this study. I-135 is a newly built asphalt pavement and the other two are gap-graded CRM overlays. Deflection data were collected with a Dynatest 8000 FWD at 21 locations at 7.5-m intervals on each test section on I-135, 22 locations on K-32, and 11 locations on US-56. For CRM asphalt mix overlays, the average surface layer coefficients from the equal mechanistic approach of analysis were found to vary between 0.11 and 0.46 with most values falling around 0.30. This indicates a lower structural layer coefficient value for the asphalt-rubber mix compared with the conventional asphalt concrete. For newly constructed CRM asphalt pavements, the structural layer coefficients varied from 0.25 to 0.48, with the average value around 0.35. These values are close to the design layer coefficient values used for conventional asphalt concrete layers. Large variabilities in computed structural layer coefficients for the rubblized jointed reinforced concrete pavement were observed. The structural layer coefficients computed for this layer varied from 0.10 to 0.35.