bluuebunny/crossref_metadata_2025 huggingface dataset:
Engine and Weight Characteristics of Heavy Heavy-Duty Diesel Vehicles and Improved On-Road Mobile Source Emissions Inventories: Engine Model Year and Horsepower and Vehicle Weight
Authors: Yoon Seungju , Rodgers Michael O. , Pearson James R. , Guensler Randall L.
Published: April 2007

Heavy heavy-duty diesel vehicles (HHDDVs) are the major mobile emissions sources of oxides of nitrogen and diesel particulate matters; emissions rates from HHDDVs vary according to their engine and weight characteristics. By considering these characteristics, air quality management agencies can improve their mobile source emissions inventories, which serve as the cornerstone of successful regional air quality management planning. To develop on-road mobile source emissions inventories, air quality agencies use the U.S. Environmental Protection Agency's mobile emissions model MOBILE6. However, modelers cannot adjust the engine and weight characteristics of the HHDDVs because the model considers HHDDVs as a single vehicle type, with national default parameter representing their engine and weight characteristics. Georgia Institute of Technology researchers investigated the engine and weight characteristics of HHDDVs, which included engine model year, engine horsepower, and vehicle weight, through a screen-line cordon survey in the 21-county Atlanta metropolitan area. Engine model year, engine horsepower, and vehicle weight characteristics were evaluated by the chi-square goodness-of-fit test to determine whether the characteristics were homogeneous with spatial location, time period, and trip type categories. The survey indicated that the average engine age was 4.5 years and average engine horsepower was 454. However, average vehicle weight varied according to the time of day with the trip type category. Findings from this study can be used as parameters in the improvement of both accurate on-road mobile source emissions inventories and regional air quality management plans. Findings can also be used for the improvement of future on-road mobile source emissions models.
Effect of Vehicle Operation, Weight, and Accessory Use on Emissions from a Modern Heavy-Duty Diesel Truck
Authors: Brodrick Christie-Joy , Laca Emilio A. , Burke Andrew F. , Farshchi Mohammad , Li Ling , Deaton Michael
Published: April 2007

The objective was to determine the effect of several variables—vehicle operation, weight, and accessory use—on emissions production during common on-road heavy-duty vehicle operations. Oxides of nitrogen (NOX), hydrocarbon, and carbon monoxide emissions from a heavy-duty diesel tractor equipped with a 1999 engine were measured continuously during on-road tests. The vehicle was operated at predetermined steady-state modes of 25, 55, and 65 mph as well as full-throttle accelerations from 0 to 25 mph and 0 to 55 mph and decelerations from 65 to 0 mph. Vehicle weight (payload) and accessory use (air-conditioning) were varied. In general, increases in gross vehicle weight from 52,000 Ib to 80,000 Ib resulted in approximately 40% or greater increases in NOX grams per mile (g/mi) emissions during the accelerations and higher-speed steady-state operations. These results were consistent with simulation model results from the National Renewable Energy Laboratory's ADVISOR model. Analysis of variance (ANOVA) and regression models were used to identify relationships between the variables and emissions. With the use of ANOVA, it was found that mode explained most of the variation in emissions and had a significant impact on all species of emissions tested. With the use of regression, a strong relationship was confirmed between steady-state modal NOX emissions per hour and horsepower ( r2 = 0.89, P <.0001). When mode and weight were added as factors in the regression model, the overall precision of NOX emissions prediction was increased and horsepower became nonsignificant.
Porous Elastic Road Surface as Urban Highway Noise Measure
Authors: Meiarashi Seishi
Published: April 2007

Highway traffic noise is a serious problem in urban areas of Japan, not only for residents along highways but also for highway administrators. Only 13% of urban highways have met the environmental standard for noise. Noise barriers cannot be used as a noise countermeasure on most highways for which access is not controlled. This problem is impeding new highway construction in urban areas. Since 1993 the Public Works Research Institute (PWRI) has been developing a new low-noise pavement called porous elastic road surface (PERS). This new pavement has a porous structure composed of granulate rubber made from used tires as its aggregate and urethane resin as its binder. It is estimated that the potential noise reduction levels in the Leq sound level exceed 10 dB (A). More than 90% of highways in urban areas would meet the standard if this noise reduction level were achieved. The general performance of PERS obtained through past development at the PWRI is examined. Results of recent research done to improve the noise reduction levels of PERS further and the first test construction using PERS in Japan are summarized. The noise measurement result at the site indicates that PERS has enough potential to solve highway traffic noise problems in urban areas of Japan.
National Scenic Byways: Diversity Contributes to Success
Authors: Kelley William J.
Published: April 2007

National Scenic Byways have both similar and diverse traits. Similarities include common intrinsic qualities, completed corridor management plans, and substantial efforts toward program goals of preserving and promoting their intrinsic qualities. Variations include corridor characteristics, land management and ownership patterns, and the maturity and capacity of byway organizations. Despite differences, most National Scenic Byways achieve a high degree of productivity as measured by planning activity, program development, and facility improvements. It is argued that the degree of diversity accommodated in the national program is a contributing factor to byway success.
Design and Operational Performance of Crossover Displaced Left-Turn Intersections
Authors: Jagannathan Ramanujan , Bared Joe G.
Published: April 2007

Although the concepts of the crossover displaced left-turn (XDL) intersection (also called the continuous flow intersection) were developed approximately four decades ago, there is no simplified procedure to evaluate its traffic performance and to compare this intersection with conventional intersections. Several studies have shown the qualitative and quantitative benefits of the XDL intersection without providing accessible tools for traffic engineers and planners to estimate average control delays and queues. Modeling was conducted on typical geometries over a wide distribution of traffic flow conditions for three different design configurations or cases using VISSIM simulations with pretimed signal settings. Some comparisons with similar conventional designs showed considerable savings in average control delay, as well as average queue length and increase in intersection capacity. The statistical models provided an accessible tool for the practitioner to assess average delay and average queue length for three types of XDL intersections. Finally, a preferred signal setting was developed for each of the five intersections of the XDL network.
Basis of the Swiss Design Standard for Roundabouts
Authors: Spacek Peter
Published: April 2007

The roundabout form of intersection underwent a huge boom in Switzerland in the 1990s. So-called compact roundabouts have proved particularly successful with regard to traffic safety; in many cases it was possible to eliminate accident "black spots" by converting existing intersections. Analysis of accident data has shown, however, that safety improvements have not produced satisfactory results at all roundabouts. Indeed, before-and-after comparisons indicate certain roundabouts actually experienced increases in the number of accidents. The causes of these negative effects appear to lie in local circumstances. A research project was launched to investigate the relationships between accident occurrence, traffic flow, and geometry in the area of roundabouts. The goal of the project was to develop basic principles for a Swiss design standard. The central importance in roundabout design of the deflection of vehicle pass-through tracks by means of the roundabout's central island was established. An insufficient deflection of the vehicle stream from the straight direction of travel results in failures to give way, increased pass-through speeds, and underestimations of these speeds by the other parties in conflict situations. These consequences are manifested in increased accident frequency.
Determining Critical Length of Grade for Geometric Design of Vertical Alignments
Authors: Torbic Darren J. , Harwood Douglas W. , Richard Karen R. , Glauz William D.
Published: April 2007

In the 2001 Green Book, critical length of grade is generally defined as the length of grade that would produce a speed reduction of 15 km/h (10 mph) for a 120-kg/kW (200-lb/hp) truck. The Green Book does not provide an appropriate tool for highway engineers to calculate critical length of grade for locations where a truck with a weight/power ratio other than 120 kg/kW (200 lb/hp) is appropriate. Research was conducted to determine the distribution of truck weight/power ratios in the current truck fleet in several regions of the United States. The results suggest that, for design purposes, a truck with a weight/power ratio of 102 to 108 kg/kW (170 to 180 lb/hp) would be appropriate for freeways in California and Colorado, although a weight/power ratio of 126 kg/kW (210 lb/hp) would be more appropriate in Pennsylvania. For two-lane highways, a 108-kg/kW (180-lb/hp) design vehicle may be appropriate in Colorado, although less powerful design vehicles in the range of 150 to 168 kg/kW (250 to 280 lb/hp) may be appropriate for California and Pennsylvania. A truck speed profile model also was developed that enables highway designers to calculate the speed profile of trucks with any given weight/power ratio and for any given vertical alignment. This design tool will improve the ability to calculate critical length of grades for any situation.
Competitive Performance Assessment of Dynamic Vehicle Routing Technologies Using Sequential Auctions
Authors: Figliozzi Miguel Andres , Mahmassani Hani S. , Jaillet Patrick
Published: April 2007

Technologies for a dynamic truckload pickup-and-delivery problem in a competitive environment by use of sequential auctions are compared. In this environment, demands arrive randomly over time and are described by pickup-and-delivery locations and hard time windows. On demand arrival, carriers compete for the loads in a second-price auction. Four fleet assignment technologies with different degrees of sophistication are tested with simulations. The technologies differ in how they deal with the combinatorial and stochastic elements of the online problem. A one-step look-ahead dynamic vehicle routing technology that tries to estimate the impacts of current decisions on serving future loads (not yet arrived) is introduced. The performance of each technology is analyzed in relation to different demand characteristics.
Approximate Procedures for Probabilistic Traveling Salesperson Problem
Authors: Tang Hao , Miller-Hooks Elise
Published: April 2007

Approximate expressions for evaluating a priori solutions to the probabilistic traveling salesperson problem (PTSP) are introduced. The approximate expressions are incorporated in heuristic improvement procedures for PTSP to provide high-quality solutions with significantly reduced computational complexity compared with that for identical improvement procedures with exact solution evaluation. The link between this approximation evaluation scheme and a metaheuristic is discussed. Additionally, a progressive approximation extension is provided. Numerical experiments were conducted to assess the effectiveness of a proposed approximate evaluation expression and the progressive approximation scheme. Experimental results indicate that improvement procedures incorporated with the approximate evaluation expressions can produce solutions comparable to those of improvement procedures with exact solution evaluation with significantly reduced computational complexity. The results also show that the progressive approximation scheme is able to provide consistently improved solutions with a considerably reduced computational effort compared with that required for a similar approach that uses exact calculation of expected length.
Incorporating Automated Vehicle Identification Data into Origin-Destination Estimation
Authors: Antoniou Constantinos , Ben-Akiva Moshe , Koutsopoulos Haris N.
Published: April 2007

A methodology for the incorporation of automated vehicle identification (AVI) data into origin-destination (O-D) estimation and prediction is presented. AVI technologies facilitate the collection of useful data, such as point-to-point travel times and subpath flows. A framework for the incorporation of AVI data into the well-established O-D estimation and prediction process is presented. Improvements are proposed for both the formulation and the inputs to the O-D estimation and prediction model. Furthermore, as the O-D estimation and prediction process is often used in the traffic estimation and prediction context, approaches to the incorporation of AVI data into other areas of the dynamic traffic assignment framework are outlined. Performance and computational issues are also considered, and the results of a case study are presented to demonstrate the approach.
Modeling Repeated Multinomial Route Choices Under Advanced Traveler Information System: Generalized Estimating Equations with Polytomous Logit Function
Authors: Abdel-Aty Mohamed , Abdalla M. Fathy
Published: April 2007

Correlated multinomial route choice data were modeled under an advanced traveler information system (ATIS). A travel simulator was used as a dynamic data collection tool. The simulator uses realistic network and real historical traffic volumes. It provides five levels of ATIS and accounts for types of delay. A 25-node and 40-link network was used. Sixty-three qualified subjects performed a total of 539 trial days. Forty-four distinct routes were chosen. The multinomial generalized estimating equation (MGEE) methodology was used with a generalized polytomous function and an exchangeable correlation structure. MGEEs account for the serial correlation between repeated choices made by the same subject as well as the correlation due to the overlapping between alternatives. The modeling results show that drivers can identify and follow the shortest path when they are provided with advice-free traffic information on all the network links. In addition, it is shown that the odds of choosing a certain shortest-path route, whether the drivers are advised or not, vary from route to route, depending on the characteristics of the route itself. It was proved that the proposed model could account for a correlation in the multinomial repeated route choices with simple computational effort, even for a large number of alternatives.
Transportation Network Optimization Problems with Stochastic User Equilibrium Constraints
Authors: Meng Qiang , Lee Der-Horng , Yang Hai , Huang Hai-Jun
Published: April 2007

A comprehensive study of static transportation network optimization problems with stochastic user equilibrium constraints is presented. It is explicitly demonstrated that the formulation of the fixed-point problem—in terms of link flows for the general stochastic user equilibrium problem in which the Jacobian matrix of link travel cost functions may not be symmetric—possesses a unique solution with mild conditions. By developing a sensitivity analysis method for the stochastic user equilibrium problem, the study proves that the perturbed equilibrium link flows are continuously differentiable implicit functions with respect to perturbation parameters. Accordingly, it can be concluded that the proposed unified bilevel programming model, which can characterize transportation network optimization problems subject to stochastic user equilibrium constraints, is a smooth optimization problem. In addition, the study presents a single-level continuously differentiable optimization formulation that is equivalent to the unified bilevel programming model. Furthermore, as a unified solution method, a successive quadratic programming algorithm based on the sensitivity analysis method is used to solve the transportation network optimization problems with stochastic user equilibrium constraints. Finally, two examples are used to demonstrate the proposed models and algorithm.
Multidepot Vehicle Routing with Uncertain Demands: Chance Constrained Approach
Authors: Miranda Pablo A. , Garrido Rodrigo A.
Published: April 2007

Distribution system design is a relevant problem that has been widely studied by researchers and practitioners in logistics and supply chain management. A stochastic programming model used to design part of the distribution system of a firm with multiple depots that face stochastic demands is presented. It is assumed that there is a fixed set of depots that serve a fixed set of customers with uncertain demands. The problem consists of finding the number of vehicles and assigning customers to capacitated vehicle routes such that the total system cost is minimum. The vehicle capacity is treated stochastically through chance constraint programming, in which the model finds a solution that presents a probability of exceeding capacity constraints lower than a fixed probability. The customers are characterized by the means and variances of their demands. The problem is modeled on the basis of a hub-and-spokes network topology, in contrast to the standard objective function of the vehicle routing problem. This modeling is considered to be included in a strategic distribution network design problem, which is typically solved by using facility location problems. Unlike previous work found in the literature, this approach simultaneously considers multiple depots and stochastic constraints. A heuristic procedure is presented along with an algorithm to find the objective function's lower bound, which allows the computation of an upper bound of the error of the heuristic solutions.
Minimal Arc Partitioning Problem: Formulation and Application in Snow Routing with Service Route Continuity
Authors: Toobaie Shahabeddin , Haghani Ali
Published: April 2007

The present research deals with a special case of emergency truck routing for snow removal or salting (snow routing) in which the objective function is primarily to minimize the number of trucks and secondarily to minimize the number of deadhead miles while the snow network is salted as much as required and the trucks' salting capacity is not violated. An additional constraint requires each truck service route to be a connected network. This route continuity constraint helps avoid confusion for truck drivers. A three-phase approach to the problem is presented: first, minimize the number of trucks; second, balance the workloads; and third, find the best routes to minimize the number of deadhead miles. The minimal arc partitioning problem (MAP) is introduced as an abstraction of the first phase (minimization of the number of trucks). MAP is stated as determination of the minimal arc partitioning of a network so that each partition (subnetwork) constitutes a connected network and so that capacity constraints are satisfied. Balancing the trucks and routing them to each subnetwork are dealt with in the other phases. The approach is applied to a real-world snow emergency network, and the results are discussed. It is demonstrated that the number of trucks can be reduced by up to 15% and the number of deadhead miles can be reduced by up to 70% compared with the number of trucks and the number of deadhead miles with the current plan. In addition, the overall algorithm is quite fast.
Test of Theory of Driver Behavior on Homogeneous Freeways
Authors: Chung Koohong , Cassidy Michael J.
Published: April 2007

A theory that can explain even some of the more puzzling aspects of freeway traffic flow is tested here. Some of the observations furnished to this end pertain to dynamic features of traffic that have not been previously verified with data. These include findings that ( a) freeway traffic can enter a semicongested state marked by a fast-moving queue in the passing lane with unqueued flow in the shoulder lane; ( b) the possible devolution of traffic to a fully congested state when vehicle speeds in the passing lane drop below those in the shoulder lane supports the contention that freeway capacity reductions can be caused by loss of driver motivation; and ( c) the transition between semicongested and fully congested traffic can propagate upstream at velocities much higher than those of ordinary kinematic waves. These and other findings are in agreement with the theory, which suggests that the theory is a reasonable description of certain driver behavior.
Structural Properties of Helbing's Traffic Flow Model
Authors: Necoara I. , De Schutter B. , Hellendoorn J.
Published: April 2007

The structural properties of the shock- and rarefaction-wave solutions of a macroscopic, second-order nonlocal continuum traffic flow model, namely, Helbing's model, are analyzed. It is shown that this model has two families of characteristics for the shock-wave solutions: one characteristic is slower and the other one is faster than the average vehicle speed. Corresponding to the slower characteristic are one-shock and one-rarefaction waves, the behavior of which is similar to that of shock and rarefaction waves in the first-order Lighthill-Whitham-Richards model. Corresponding to the faster characteristic are two-shock and two-rarefaction waves, which behave differently from the previous type in the sense that the information in principle travels faster than average vehicle speed, but in Helbing's model this inconsistency is solved by the addition of a nonlocal term. For the Helbing model the shocks do not produce negative states as other second-order models do. The formulas for the solution of the Riemann problem associated with this model in the equilibrium case are also derived.
Drivers' Use of Deceleration and Acceleration Information in Car-Following Process
Authors: Sultan B. , Brackstone M. , McDonald M.
Published: April 2007

Understanding driver behavior is important for the development of many applications such as microscopic traffic simulation models and advanced driver assistance systems. The car-following process is an important phase of driving behavior and takes place when a driver follows a lead vehicle and tries to maintain distance and relative speed within an acceptable range. A key to improving knowledge of driver behavior during this process is determining the information perceived by drivers that could influence their decisions. It has been believed for some time that the main kinematic parameters that affect driver judgment in car following are the relative speed, the distance separation, and the absolute speed. The research described investigated whether drivers are also able to use information on the lead vehicle's deceleration or acceleration during the car-following process through experimental validation of current car-following hypotheses. For this research, an instrumented vehicle was used to collect a large database of car-following time sequences, the analysis of which showed strong evidence that drivers are able to perceive information such as the deceleration or acceleration of the vehicle being followed, although no empirical relationship was determined. An example demonstrating the importance of such perception shows that modeling a driver trying to avoid a collision with a lead vehicle would lose 20% of its fit accuracy if the lead-vehicle acceleration state were not considered.
Application of Relaxation Procedure for Lane Changing in Microscopic Simulation Models
Authors: Cohen S.
Published: April 2007

Lane-changing submodels in microscopic traffic simulation models require the implementation of a relaxation procedure. The basis of this requirement is the observation from field data that both a vehicle performing a lane change into a short gap and its new follower maintain persistently short following distances for a significant period (20 s or more), gradually increasing to equilibrium values. A proposed approach involves a temporary reduction in the vehicle sensitivity factor of the car-following component in the FRESIM submodel of CORSIM for a user-specified period. The relaxed lane-changing model was implemented on a spreadsheet, and a series of values of the relaxation time was used in a scenario in which an initially short value for the time headways between the leader, lane changer, and follower was assumed. The results for speed and time headways indicate qualitative agreement with the field data. The same scenario was run with the unrelaxed procedure in the existing FRESIM model, and the results for the speed and time headways were in disagreement with the field data. From these results, it was concluded that the lane-changing system currently imbedded in the FRESIM model was invalid. Subsequently, the relaxed lane-changing model was implemented in FRESIM, and a merge scenario was executed. It was seen that the value of the sensitivity factor required to reproduce any particular merge capacity in this revised model increased to physically realizable values as the relaxation time is increased, whereas non-physical values were required in the existing FRESIM model to produce equivalent merge capacities.
Extended Speed Gradient Model for Mixed Traffic
Authors: Jiang Rui , Wu Qing-Song
Published: April 2007

The speed gradient (SG) model was extended to a mixture of different types of vehicles. The extended SG model was used to study the steady state of the mixed traffic flow system, the formation of traffic jams at a traffic light switching from green to red, the dissolution of jams at a traffic light switching from red to green, and the local cluster effect of the mixed traffic system. The simulation result are qualitatively consistent with everyday experience.
Relationships Between Occupancy and Density Reflecting Average Vehicle Lengths
Authors: Kim Youngho , Hall Fred L.
Published: April 2007

The linearity of the occupancy-density relationship is investigated by studying the relationship mathematically across a wide range of traffic situations as well as by plotting values of both variables on the occupancy-density diagram. The literature does not show general agreement on the linearity of the relationship. The relationship is shown to be practically linear because the nonlinear factor mathematically derived does not have noticeable effects on the linearity of the relationship. However, the plot of both variables on the occupancy-density diagram shows that the relationship is influenced by varying average vehicle lengths and can be interpreted as being either linear or nonlinear. The proportion of long vehicles (trucks) is tested empirically and is shown to have large effects on the linearity of the relationship.
Automobile Drivers' Perceptions of Service Quality on Urban Streets
Authors: Pécheux Kelley Klaver , Flannery Aimee , Wochinger Kathryn , Rephlo Jennifer , Lappin Jane
Published: April 2007

The Highway Capacity and Quality of Service Committee of TRB, which oversees the development of the Highway Capacity Manual, has formally recognized a need to improve the current level-of-service (LOS) methodologies. Among the concerns about the methodologies is the extent to which LOS estimates correspond to road users' perceptions. In recognition of these concerns, the objectives of this study were to ( a) develop and test a methodology to obtain drivers' opinions with regard to urban street quality of service (QOS), ( b) apply the methodology to identify the factors that affect drivers' perceptions of QOS on urban streets, and ( c) provide a qualitative foundation for the development of quantitative QOS tools that are based on the perceptions of drivers. This study used an in-vehicle field approach to determine the factors that affect automobile drivers' perceptions of service quality on urban streets. While driving on a preselected route, 22 participants in four cities were asked to speak aloud about their driving experience and the factors that influenced their perception of service quality. Afterward, drivers also completed a written questionnaire. The drivers expressed their opinions about a wide range of issues, including simple observations, more detailed evaluations, and broad concerns related to the roadway environment. From the drivers' comments, 40 factors were identified as relevant to their perception of service quality on urban streets. The authors believe that by identifying a wide range of factors that influence drivers' perceptions of service quality on urban streets, this study has increased the knowledge and understanding of the needs and values of automobile drivers on urban streets and has laid the groundwork for future studies aimed at developing quantitative QOS tools and models.
Movement Capacity at Two-Way Stop-Controlled Intersections
Authors: Luttinen R. Tapio
Published: April 2007

Potential capacity at an unsignalized intersection can be described as a conditional expectation from which the capacity equations for the most common headway distributions are easily obtained and each term in the equation finds an interpretation. The movement capacity of Rank 3 streams is adjusted for both Rank 2 queues and the modified headway distribution and lower flow rates during the free-departure periods of Rank 2 streams. The resulting movement capacities are higher than those of the Highway Capacity Manual (HCM 2000), especially at low major-stream flow rates. The Rank 4 stream adjustment factors are shown to be multiplicative even across streams of different ranks. The extra correction in HCM 2000 is, in the light of this theory, unnecessary.
Synergies of Bus Rapid Transit and High-Occupancy Toll Lanes: Simulation of Bus Rapid Transit in Congested Corridor with Roadway Value Pricing
Authors: Barker William G. , Polzin Steven E.
Published: April 2007

The costs and benefits of integrating two major areas of urban transportation enhancement—high-occupancy toll (HOT) lanes and bus rapid transit (BRT)—are explored. The goal is to assess a synergistic strategy of providing premium public transit services in conjunction with roadway pricing strategies. The use of BRT is specifically addressed in the context of a congested urban travel corridor with roadway value pricing. A simple simulation is used to determine those circumstances in which BRT might be an effective element of a multimodal value-pricing corridor strategy. The model used is a variation of SMITE (Spreadsheet Model for Induced Travel Estimation) extended to include managed lanes developed previously by DeCorla-Souza at FHWA. The analysis simulated some alternatives differing from those included in the original DeCorla-Souza assessment of options for the Capital Beltway in Northern Virginia. This is currently a 14-mi-long, 8-lane freeway with no restricted lanes. Seven alternatives are examined. Six of the alternatives place an additional lane in each direction, for a total of 10 lanes. The seventh alternative takes a lane in each direction to provide a special-purpose lane in each direction. The findings suggest that both roadway pricing and BRT compare favorably with toll-free facilities and conventional transit. Taking a lane for a combined HOT facility with BRT might be particularly cost-effective in select locations.
Computer-Assisted Scheduling and Dispatching Systems for Paratransit Brokerage and Coordination: State Strategies for Implementation
Authors: Pagano Anthony M. , Metaxatos Paul , Morreale Alicia
Published: April 2007

In times of increasingly selective federal and state funding possibilities, paratransit providers need to consider whatever efficiencies can be gained through operational improvements and coordination with other providers. Both objectives can be facilitated through the implementation of computer-assisted scheduling and dispatching (CASD) systems. However, the level of realized positive impacts depends on the specifics of each implementation plan and overall deployment strategy. Moreover, with increasing numbers of local CASD system implementations, state departments of transportation have only recently realized the need for statewide strategies regarding future deployments of such systems. Potential strategies and results from a survey of states that have attempted statewide CASD system implementations are discussed.
Analysis of Delay Caused by Midblock Jeepney Stops with Use of Simulation
Authors: Palmiano Hilario Sean O. , Yai Tetsuo , Ueda Shimpei , Fukuda Daisuke
Published: April 2007

Public transit enjoys an almost 80% share of trips in Metro Manila, and the most widely used is the paratransit vehicle called the jeepney. These 18- to 22-seat vehicles, which evolved from American army service jeeps left after World War II, provide inexpensive and convenient door-to-door service but cause disruptions in traffic flow because of aggressive and problematic driving behavior, particularly when stopping to pick up or unload passengers. Other vehicles are observed to experience delays, especially in the vicinity of midblock jeepney stops with high passenger demand. An overview of work done in building and validating a traffic microsimulation program focuses on modeling the distinctive stopping behavior of jeepneys that considers both transit vehicle and passenger agents. Propensity for nonobservance of lanes and aggressive lateral movements of general traffic are considered in the model. There is also a discussion of the result of simulation experiments that used the developed simulation model called JSTOPSIM and are designed to analyze trends on average vehicle delay experienced by through vehicles as passenger demand and volume of transit and non-public transit vehicles vary. The capability to quantify objectively delays attributable to jeepney stops is important in advocating policies to improve design and operation for the improvement of the public transit system as a whole.
Recruitment, Selection, and Retention of Personnel at North Carolina Community Transportation Systems: Findings and Recommendations from a Study
Authors: Cook Thomas J. , Lawrie Jud
Published: April 2007

The hiring and the retention of personnel have been a long-standing issue in the public transportation industry. This involves finding and recruiting potential employees, selecting and hiring the most qualified candidates, training and developing employees, monitoring performance and retaining employees, and reducing excessive turnover and absenteeism. While human resources topics have typically been investigated at urban transit systems operating fixed-route services, hiring and retention have not been studied extensively at smaller rural transit systems operating demand-responsive transit services. This research focused on such rural systems and on the various factors that most impact on the issue at nine North Carolina community transportation systems. This effort included various human resources policies and practices such as recruiting, selecting, compensating, training, evaluating, and motivating. Practices at the nine case study systems and recommendations to improve policies and procedures are described.
Introducing and Sustaining Accessible Transport: Social and Physical Challenges
Authors: de Boer Enne
Published: April 2007

Improvements in transportation accessibility are being made in the Netherlands. The Ministry of Transport issued leaflets with suggestions to direct development, and Delft University of Technology was asked to illustrate these suggestions with practical examples. In the course of this effort, enough material was collected to present a comparative state of the art. Bus systems in seven areas were critiqued. The assessment showed that progress in certain aspects was more prominent than in others. Low-floor buses are being introduced nearly everywhere, but the adaptation of bus stops is lagging behind. Ideas about bus interiors are rather confused. One essential feature, the seat, is treated unsatisfactorily. The driving behavior of bus drivers often does not take vulnerable passengers into account. Accessibility actually decreases in some cases because of insufficient specifications in contracts. Further progress in accessibility seems to require more guidelines and information campaigns.
Analysis of Handicapped Parking at Auburn University
Authors: Capps Christopher Shaun , Bowman Brian L.
Published: April 2007

The number of handicapped spaces that serve a facility is largely determined on the basis of Americans with Disabilities Act of 1990 (ADA) guidelines, which do not take into consideration the actual land use that a parking lot serves. The ADA guideline of basing the number of handicapped spaces on the size of the parking lot does not work well for land uses such as universities. The following study looks at the campus of Auburn University in order to develop a model that will base the number of handicapped spaces on the characteristics of the facility the parking lot serves. Models were developed with occupancy rates, turnover rates, and facility characteristics as variables. A model based on the peak period occupancy rates was used to determine the recommended number of handicapped parking spaces. Using the peak period occupancy rate generates the proper number of spaces required to accommodate the demand.
Mobile Navigation Guide for the Visually Disabled
Authors: Huang Bo , Liu Nan
Published: April 2007

A location-aware navigation system has been developed and implemented for the visually disabled or visually impaired; the system is designed to improve individuals' independent mobility. This self-contained, portable system integrates several technologies, including mobile personal digital assistants, voice synthesis, a geographic information system (GIS), and a differential Global Positioning System (DGPS). The system is meant to augment the various sensory inputs available to the visually impaired user. It provides the user with navigation assistance, making use of voice cues iterating contextual building and feature information at regular intervals, through automatic GPS readings and a GIS database. To improve the efficiency of the retrieval of contextual information, an indexing method based on road segmentation was developed to replace the exhaustive search method. Experimental results show that the performance of the system on searching the buildings, landmarks, and other features around a road has been significantly improved by using this indexing method.
Developing and Validating a Tool to Estimate Highway Construction Project Costs
Authors: Kyte Cheryl A. , Perfater Michael A. , Haynes Stephen , Lee Harry W.
Published: April 2007

In May 2002, Virginia's commonwealth transportation commissioner directed the Virginia Transportation Research Council (VTRC) to develop an improved method to estimate the project costs of the Virginia Department of Transportation (VDOT). After an effort to look across the United States and within VDOT for proven estimation methods, the study group found that VDOT's Fredericksburg district had been using an estimation worksheet for several years that produced consistent and reliable results. The study group concluded that no other methods examined had the specificity and inclusive nature of this tool. VTRC staff and the Fredericksburg staff who had developed the model expanded it by collecting extensive project data and obtaining evaluations of VDOT project management personnel statewide. The existing worksheet with roadway and bridge estimates was expanded to include construction engineering, to be applicable for Interstates and to generate estimates for right-of-way and utilities costs. Data on completed projects were collected from all VDOT districts to help calibrate the model further to account for cost variations across the state. The study group recognized early that a strong focus on project scoping was essential to ensuring accurate project estimation. Therefore, the group relied on input from the VDOT scoping committee that had been charged with exploring and developing recommendations for improving the scoping process. Testing of the tool was completed in the summer of 2003. Analyses of many completed VDOT construction projects showed that the estimation model yielded results that on average differed from actual final project costs by 22%.
Transportation Asset Management Today: Communities of Practice in the Transportation Industry
Authors: Winsor Jeromie , Adams Louis H. , McNeil Sue , Ramasubramanian Laxmi
Published: April 2007

Asset management is defined by FHWA as "a systematic process of maintaining, upgrading, and operating physical assets cost-effectively." This emerging discipline is evolving as researchers develop asset management guides, states implement specific components of it, and all units of government work to define what asset management means to them and tailor it to the needs of their organization. To help facilitate communication among these stakeholder groups, AASHTO and FHWA developed a website-based virtual community of practice (CoP). This CoP is a self-defined group of practitioners with an interest in transportation asset management. The website, Transportation Asset Management Today (TAMT), provides access to relevant links and a calendar of events and allows individuals to register for topics that match their personal interests, view reference materials, and post questions and ideas on discussion boards. Why an Internet CoP is an appropriate venue for advancing transportation asset management education and practice is discussed. Also provided are an overview of CoP theory and a description of how CoPs are being used in the private and public sectors to manage knowledge and share best practices. Finally, the history, structure, and content of the TAMT website are discussed, and a preliminary evaluation based on site usage and other observations is offered.
Comparative Analysis of Customer Response to Online Traffic Information in Two Cities: Los Angeles, California, and Seattle, Washington
Authors: Petrella Margaret , Lappin Jane
Published: April 2007

A comparative analysis was performed of customer response to online traffic information in the Los Angeles, California, and Seattle, Washington, regions. A voluntary, online survey was administered to users of the Travel Advisory News Network and SmarTraveler websites in Los Angeles, and a similar survey was performed on the Washington State Department of Transportation Traffic Conditions website. This comparative study finds that the demographic profile of users is similar in the two regions: users tend to be male, well educated, upper income, employed, and 26 to 45 years of age. Users in both samples were also more technologically savvy than the general population. Despite these similarities, the data also reveal that location matters, as customers in Los Angeles experience significantly longer commutes and greater congestion and volatility in traffic conditions. While customers in both regions gave positive assessments of the traffic websites, Seattle respondents were more enthusiastic. On several dimensions, Seattle respondents expressed more intense support for their site. Moreover, Seattle customers were more likely to benefit from the service, with greater numbers agreeing that online traffic information saved them time and reduced the stress of traveling. An analysis of the data indicates that underlying traffic conditions in the two regions bear greatly on customers' response to the service. The greater congestion and volatility in Los Angeles increase customer demand for up-to-the-minute information and undermine customers' expectation that any information service can provide much relief.
Using Decision Trees to Improve the Accuracy of Vehicle Signature Reidentification
Authors: Tawfik Ahmed Y. , Abdulhai Baher , Peng Aidong , Tabib Seyed M.
Published: April 2007

Vehicle reidentification is the process of tracking a vehicle along a highway as it crosses detection stations. Inductive loop detectors are by far the most widely deployed vehicle detectors. In the present work, vehicle reidentification is performed by combining vehicle-specific information (length and electromagnetic signatures) and some contextual information (lane, speed, and time) to form a decision tree. This approach provides a specific decision tree for tracking vehicles along each highway section. After training, the decision tree successfully classified about 95% of the unseen test records—a significant improvement relative to the literature and our own previous work on the same data. This success rate has been consistently obtained from two data sets: one consisting only of passenger vehicles and another consisting of a representative traffic mix.
Using Microscopic Simulation to Evaluate Potential Intelligent Transportation System Strategies Under Nonrecurrent Congestion
Authors: Chu Lianyu , Liu Henry X. , Recker Will
Published: April 2007

A microsimulation method is presented for evaluating the effectiveness of potential intelligent transportation system (ITS) strategies under nonrecurrent congestion. The evaluated ITS strategies include incident management, adaptive ramp metering, traveler information systems, arterial management, and a combination of those strategies. These strategies are implemented and evaluated over a road network in Irvine, California, with the microsimulation model PARAMICS. The evaluation results show that all ITS strategies have positive effects on network performance. Because of the network topology (one major freeway with two parallel arterial streets), real-time traveler information has the greatest benefits among all single ITS strategies. However, a combination of ITS strategies can further increase benefits.
Algorithm for Predicting Inattentive Signal Violators in an Infrastructure-Based Intelligent System
Authors: White Bryon , Ferlis Robert
Published: April 2007

In June 2003, the FHWA introduced the first intelligent intersection, capable of assisting drivers in avoiding right-angle collisions that typically occur at intersections. One of the concepts that intelligent collision-avoidance systems displayed was a violator warning system, consisting of an illuminated sign with strobe lights to alert distracted drivers that they may violate an approaching red signal. Proposed is a novel approach for creation of an algorithm to predict and alert likely inattentive signal violators in time for them to react to an infrastructure-based warning. The algorithm is based on comparing velocity and acceleration data of vehicles traveling at free-flow speeds through an intersection with data from alert motorists stopping for a red signal on the same approach. Kinematic data were obtained at four intersections for two sets of motorists, those who were stopping for a red light and those who were going through a green light. It was presumed that inattentive violators act identically to attentive drivers with a green signal. Comparison of speed and acceleration profiles revealed distinct differences that could be used to distinguish into which subset a given vehicle would fall, well in advance of the intersection. These comparisons yield a simple, economical, and site-specific algorithm for detecting inattentive motorists about to violate a signal.