bluuebunny/crossref_metadata_2025 huggingface dataset:
Do Employee Commuter Benefits Reduce Vehicle Emissions and Fuel Consumption?
Authors: Herzog Erik , Bricka Stacey , Audette Lucie , Rockwell Jeffra
Published: May 2018

A survey of firms recognized as best workplaces for commuters (BWC) was conducted in the fall of 2004. The purpose of the survey was to determine the difference between the commuting patterns of employees who receive employee commuter benefits, such as those offered by BWCs, and those who do not and to estimate the resulting saving in trips, vehicle miles traveled (VMT), and emissions and fuel consumption. Employers recognized as BWCs in the Denver, Colorado; Houston, Texas; San Francisco, California; and Washington, D.C., metropolitan areas were randomly sampled and recruited into the survey with a combination of telephone and e-mail communications. The results of this survey indicated that when employers provide employees with incentives to commute by means other than driving alone, significant percentages take advantage of these benefits. Comprehensive benefits packages such as those enjoyed by commuters in the BWC group, with financial incentives, services (such as a guaranteed ride home and carpool matching), and informational campaigns, appear to produce reductions of trips, VMT, pollutants, and fuel consumption of about 15% even by the use of conservative assumptions. Benefits packages offering services and information but not offering financial incentives appear to produce reductions of about 7% by the use of conservative assumptions.
Improving Urban Mobility Management
Authors: Musso Antonio , Corazza Maria Vittoria
Published: May 2018

Congestion, energy consumption, pollution, and the need to increase transport system sustainability are top-priority problems in urban areas. Most European cities are beset with these issues; hence, the European Commission financially supports projects aimed at reducing the negative effects of vehicles on the environment by increasing accessibility, optimizing economic resources in transport management, and improving citizens’ quality of life. Presented are the main findings of one of these projects, Multi-Initiatives for Rationalised Accessibility and Clean Liveable Environments (Miracles), which focused on the measures implemented by the Rome municipality during the project, including incentives to attract passengers to transit and disincentives to the use of private cars. In particular, the most relevant aspects, such as restriction of vehicle access to the city center, road pricing, goods delivery reorganization, and the development of collective taxis, are analyzed because of their innovative features and their potential to achieve improvements. Also discussed is the suitable methodology, applied in the Rome case study, for controlling and validating all the implementation steps. Particular attention was paid to the simulation of scenarios that can be used to assess the feasibility of pricing-related measures and how they can affect the built environment. In conclusion, the paper outlines users’ reactions to the restriction policy changes.
Exploratory Analysis of Crossing Difficulties for Blind and Sighted Pedestrians at Channelized Turn Lanes
Authors: Schroeder Bastian J. , Rouphail Nagui M. , Emerson Robert S. Wall
Published: May 2018

This paper presents the findings from a paired comparison study of blind and sighted pedestrians judging crossing opportunities in traffic from the roadside at three channelized turn lane (CTL) locations. It is motivated by the belief that the geometric nature of CTL facilities and the lack of signal control at the pedestrian crossing are factors that may negatively affect the delay and safety for blind pedestrians. Pedestrians waiting at the curb must judge the traffic moving in a circular motion, and they must deal with a significant amount of background traffic (i.e., noise) present at the main intersection. The findings show that crossings at all CTL crossing locations are significantly more difficult for blind pedestrians than for sighted pedestrians. Blind pedestrians tend to face a greater risk and a greater amount of delay. Furthermore, the research shows that conflicting traffic flow in the turn lane has a significant effect on crossing performance for both pedestrian groups; however, the effect of noise-generating background traffic on blind pedestrian crossings is not significant. The study also concludes that for this experiment the location of the crosswalk (in the center of the turn lane or at the downstream end) does not have a significant effect on crossing judgment performance.
Native American Transit
Authors: Boyles Benjamin , Brinton Erin , Dunning Anne , Mathias Angela , Sorrell Mark
Published: May 2018

For years, a lack of transportation options has held Native Americans captive. Without access to services and employment, this subset of the population has a history of high unemployment, poor health, and a lack of education. Public transit is viewed as a way to address this mobility challenge; however, many barriers to the provision of tribal transit exist. This paper examines the current state of transit on reservations through historical and environmental contexts, discusses the necessity of transit for Native Americans, examines case studies, and describes funding and legislative frameworks with the goal of presenting ideas on how Native Americans might overcome the barriers to transit provision.
Is the Driving Experience of Older Women Changing?
Authors: Rosenbloom Sandra
Published: May 2018

Older women currently have travel patterns substantially different from those of older men even when they are licensed to drive. These differences have different safety and mobility implications for older women in the future—if they persist—but equally important consequences if they do not. This paper shows that women drivers at all ages drive less often and for fewer miles than men of comparable ages; as a result, in the next three decades most women will enter their retirement years with substantially less driving experience than their licensing status might indicate. The differences in travel patterns and driving experiences between women and men are likely to persist, and policy makers must address both their safety and mobility consequences. There is a significant need to conduct the kind of safety and mobility research that will inform intelligent policy development and planning strategies for what has been called the feminization of aging.
Hidden Epidemic of Maternal, Fetal, and Neonatal Mortality and Injury from Crashes
Authors: Weiss Harold B.
Published: May 2018

From 1975 to 2001, the average annual number of vehicle miles driven by women of reproductive age increased from 3,721 to 8,258. This increase resulted from a combination of factors, including increased employment, population growth, urban sprawl, inadequate mass transportation, and rising affluence. Unfortunately, this boost in motor vehicle use among young women has had a major unintended consequence: it has led to a substantial increase in maternal and fetal exposure to the violence of motor vehicle crashes. Tragically, along with the higher levels of exposure of pregnant women to motor vehicle crashes have come the increasingly better understood impacts of pregnancy-related crash-associated deaths, injuries, and other adverse outcomes on pregnant women, fetuses, and infants. From a mortality perspective alone, it has been estimated that the rate of fetal deaths due to motor vehicle crashes now exceeds the rate of infant deaths due to motor vehicle crashes by a factor of 7. Yet, despite the documented risks and concerns from empirical studies, few crash and injury data systems accurately track and capture the magnitudes and trends of these events and their outcomes. This paper focuses on (a) societal changes that have led to the problem, (b) deficiencies in crash and transportation data systems that have led to its neglect, (c) the magnitude of the problem and the nature of related adverse fetal outcomes derived from recent research, and (d) steps that need to be taken to improve the tracking of pregnancy-related crashes so that they become more visible and a higher priority for transportation research and safety.
Nationwide Survey of Transportation Planning Courses
Authors: Zhou Jiangping , Sööt Siim
Published: May 2018

This paper reports on a nationwide survey that was conducted from November 2004 through April 2005. The survey is part of a project titled the National Transportation Planning Course Syllabus and Associated Case Studies, funded by the Dwight David Eisenhower Transportation Fellowship program at the U.S. Department of Transportation. The primary objective of the survey was to determine what topics are currently being covered and their level of emphasis. The secondary objective was to identify topics for which educators would use case studies and references provided by the U.S. Department of Transportation. Instructors of transportation planning courses from 47 universities were chosen for the survey, and they returned 32 completed survey instruments. On the basis of the survey efforts, it was found that, first, the survey and the project that it serves can be useful in improving transportation planning instruction at U.S. universities; second, the survey and the project were welcomed by most universities and educators surveyed; third, the survey results can potentially be used for multiple purposes; fourth, not having a list of the institutions offering a transportation planning course(s) posed challenges for sample selection for the survey and validation of the survey results; and fifth, it is difficult to design a survey instrument for a discipline such as transportation planning, which is dynamic and ever changing.
Robust Regression Methods for Traffic Growth Forecasting
Authors: Kingan Robert J. , Westhuis Todd B.
Published: May 2018

Least-squares regression has been applied as a tool to understand traffic growth patterns and to predict future growth. Specifically, given a set of historical annual average daily traffic (AADT) values for a location, regression can be used to summarize traffic growth patterns and to predict growth. However, this technique is vulnerable to outliers because standard linear regression techniques can produce arbitrarily large errors in their results if points are badly placed. The situation is made worse when thousands of traffic sites are analyzed at once because it is infeasible to examine each set of regression results individually. In this paper two outlier detection and removal techniques and one robust regression technique are compared with simple least-squares regression for accuracy in traffic growth prediction, with both linear and log-linear models of traffic growth on historical AADT values for several thousand sites in the state of New York. Each method was evaluated by the median absolute error in predictions being computed for 1 year, 4 years, and 8 years beyond the modeled values and also by the mean percent error being computed, giving each site equal weight. When all sites were equally weighted, the robust regression technique produced significantly better results than either plain regression or outlier detection techniques. Using median absolute error, none of the robust techniques produced significantly more accurate results than ordinary regression.
Performance Evaluation of Bituminous Surface Treatment Using Third-Scale Model Mobile Loading Simulator
Authors: Lee Jusang , Kim Y. Richard , McGraw Emily O.
Published: May 2018

This paper presents a new test protocol for the performance evaluation of bituminous surface treatments (BSTs) using the third-scale Model Mobile Loading Simulator (MMLS3). The BST performance characteristics covered by this protocol include aggregate retention, bleeding, skid resistance, aggregate embedment depth, cracking, and rutting. In this study, the new MMLS3 BST performance test method was applied to evaluate effects of various mix parameters on aggregate retention and bleeding; these parameters include aggregate and emulsion application rates, fines content, and aggregate gradation. Results demonstrate that the BST performance test method developed in this study is an excellent means of supporting current BST design and evaluating effects of various factors on performance of BSTs.
Comprehensive Evaluation of New Integrated Freeway Ramp Control Strategy
Authors: Xin Wuping , Hourdos John , Michalopoulos Panos G.
Published: May 2018

A new integrated ramp control strategy, recently deployed by the Minnesota Department of Transportation in the Twin Cities metropolitan area, is evaluated. This strategy, stratified zone metering (SZM), takes into account real-time ramp demand and queue size information and aims to strike a balance between two competing objectives: improving freeway efficiency and preventing excessive ramp delays. In this study, the SZM strategy was compared to the earlier ZONE metering strategy as well as to the no-control alternative. Comprehensive metrics were generated through rigorous microsimulation to assess critical aspects of the strategy's performance. The evaluation results are consistent with qualitative field observations and confirm that SZM strategy improves freeway efficiency when compared with the no-control alternative, reduces freeway travel time and delay, improves freeway speed, smooths freeway flow, and reduces the number of stops. More important, excessive queue spillbacks and ramp delays were significantly reduced under SZM control when compared with the earlier ZONE metering strategy. However, the nonrestrictive metering rates under SZM may cause the freeway proper to be overloaded; this leads to compromised freeway performance as compared with the more restrictive ramp control. This is especially true for heavy traffic demands, when higher ramp volumes are allowed on the freeway.
Real-Time Estimation of Critical Occupancy for Maximum Motorway Throughput
Authors: Kosmatopoulos Elias , Papageorgiou Markos , Manolis Diamantis , Hayden Jill , Higginson Roger , McCabe Keith , Rayman Nanu
Published: May 2018

The local ramp metering strategy ALINEA aims at stabilizing downstream motorway occupancy near critical occupancy to achieve maximum motorway throughput. Two previously proposed real-time estimation schemes for the critical occupancy are fine-tuned, modified, and evaluated by use of extensive traffic data from eight locations of the UK M6 motorway. The evaluation results indicate satisfactory estimation accuracy, rapid tracking behavior, and high robustness for measurement noise, detector failures, and different kinds of traffic conditions. The reported investigations open the way to field implementation of the adaptive AD-ALINEA ramp metering strategy that incorporates real-time estimation of critical occupancy.
Improving Minnesota's Stratified Ramp Control Strategy
Authors: Feng Baichun , Hourdos John , Michalopoulos Panos G.
Published: May 2018

Minnesota's most recent stratified zone ramp metering (SZM) strategy, the successor of the ZONE metering algorithm, has been deployed in the Minneapolis–St. Paul area since late 2002. The SZM strategy is intended to maximize freeway throughput while keeping ramp waiting times below a predetermined threshold. Preliminary evaluation results confirmed the overall effectiveness of the SZM strategy but also revealed that the freeway performance was compromised by the restrictive maximum ramp waiting constraint. Consequently, improvements were sought. These focus on a better determination of the minimum release rate for each ramp and its integration with the overall SZM strategy. Both the current and the enhanced SZM strategies are tested in two freeway sites under various demand scenarios through a state-of-the-art microscopic simulator. The simulation results indicate that the enhanced SZM strategy is effective for delaying and decreasing the freeway congestion and results in smoother freeway traffic flow compared with the original SZM strategy without violating the maximum ramp delay requirement.
Assessing Weather, Environment, and Loop Data for Real-Time Freeway Incident Prediction
Authors: Songchitruksa Praprut , Balke Kevin N.
Published: May 2018

Weather, environment, and loop data conditions are promising indicators for real-time freeway incident prediction. The ability to predict the likelihood of selected incident types by using weather and environment data was examined. Loop detector data were analyzed for conditions useful for in-lane incident prediction. Nonnested and nested multinomial logit models were estimated with data from selected freeways in Austin, Texas. The estimation results revealed that factors such as visibility, time of day, and lighting condition are significant determinants of incident type, whereas 5-min average occupancy and coefficient of variation in speed are strong predictors of in-lane freeway accidents.
Feasibility Assessment of Metropolitan High-Occupancy Toll Lane Network in Atlanta, Georgia
Authors: Meyer Michael D. , Saben Larry , Shephard Whitney , Drake Daniel E.
Published: May 2018

High-occupancy toll (HOT) lanes have become an important consideration in metropolitan areas where a limited ability to expand the road network leads officials to examine ways to use existing road capacity more efficiently. A feasibility study of a HOT lane network was done in the Atlanta, Georgia, metropolitan area. Although the concept of HOT lanes is not new, how one analyzes a regional HOT network with existing travel demand models has not been reported in the literature. Results are presented of market research and of a systems-level analysis that were used to examine the feasibility of a regional HOT network in Atlanta. How such a feasibility analysis can be undertaken is illustrated, and policy implications are noted.
Cheaper Gas and More Expensive Shoes
Authors: Sorensen Paul A.
Published: May 2018

With mounting concern about current social and environmental challenges, the notion of sustainable development—a paradigm calling for the integration of economic, social, and environmental goals—has gained increasing popularity in recent years. Within the transportation arena, sustainability advocates have argued for reducing reliance on the private automobile and seeking instead to foster alternative modes such as transit, biking, and walking; and many cities are actively pursuing this goal. Yet even the most concerted local efforts can be undermined by contradictory policy frameworks at higher levels of government, and a recent proposal for transportation finance reform in California serves as a good case in point. Intended to enhance the reliability of highway revenues, the proposal would eliminate a 5% sales tax on gasoline and replace it with a 0.25% increase in the general sales tax specifically earmarked for transportation. Basic economic analysis shows clearly, however, that eliminating the sales tax on gasoline would stimulate additional miles driven within the state, leading in turn to increased highway congestion and vehicle emissions. At the same time, increasing the general sales tax would shift a greater financial burden onto the shoulders of nondrivers from lower-income groups. In short, the recent California proposal, if enacted, would work counter to the three goals of sustainability—economic efficiency, social equity, and environmental responsibility—and surely frustrate local efforts to reduce reliance on the automobile.
Regional Study of Value Pricing in the Dallas–Fort Worth Region, Texas
Authors: Tiedeman Jane L. , Straus Alan H.
Published: May 2018

The Dallas–Fort Worth region, Texas, is one of the most congested urban areas in the United States. As the region has experienced unprecedented growth in population and business activity, traffic congestion and delay have continued to worsen. With additional vehicles on the region's freeways and a shortage of land and resources required to build more roads, the region's transportation leaders adopted a progressive approach to managing the increasing congestion—by applying value pricing to operate the transportation system more efficiently. The region's metropolitan planning organization, the North Central Texas Council of Governments (NCTCOG), was awarded a grant from FHWA to study a regional approach to value pricing. URS Corporation worked with NCTCOG and its partners, the Texas Department of Transportation, Dallas Area Rapid Transit, North Texas Tollway Authority, Denton County Transportation Authority, Fort Worth Transportation Authority, and Texas Transportation Institute, to undertake the only major regional investigation of value pricing in the country. The study included review of a broad range of value pricing concepts and information from other projects to establish the most appropriate screening criteria for this region. The screening criteria were applied to all existing and planned freeways, tollways, and HOV facilities to identify those corridors showing the highest potential for immediate action. The study, which was completed in July 2005, resulted in the following products: (a) regional guidelines for implementing value pricing, (b) recommendation for a demonstration project (IH-30), and (c) a long-term mechanism for incorporating value pricing in the highway development process.
Econometric Estimation of Motor Fuel Sales with Incomplete Data
Authors: Vilain Pierre , Prince Ryan
Published: May 2018

A methodology is presented for developing indirect estimates of cross-border sales of motor fuels when data on price differentials are not available. The extent of motor fuel sales occurring on Native American tribal reservations is not precisely known, as no existing data source provides a comprehensive survey of on-reservation sales. Significant unreported sales could create bias in the attribution process used by FHWA to apportion each state's share of federal tax receipts. A methodology is developed to estimate the magnitude of fuel sales on Native American tribal reservations. As significant tax rate differentials may exist, prices on and off reservation may vary considerably. For the most part, these price differentials are not observed, and doing so would require a comprehensive (and expensive) survey. The model described does not rely on knowing the actual price differential but rather generates indirect estimates of sales to nonresidents of the tribal areas. This is done by comparing predicted sales in counties adjacent to Native American tribal reservations with service stations (generated by the model) with actual sales. The resulting estimates suggest that for counties adjacent to tribal reservations with significant fuel sales, cross-border sales may account for as much as 8% of total consumption. These results are robust to numerous model specifications.
Design of Safe Urban Roadsides
Authors: Dumbaugh Eric
Published: May 2018

To date, there has been little examination of the area of roadside safety on nonfreeway urban roads. To understand better the design of safe roadsides in urban environments, this study used negative binomial regression models to examine the safety effects of three roadside design strategies: widening paved shoulders, widening fixed-object offsets, and providing livable-street treatments. The model results indicated that of the three strategies, only the livable-streets variable was consistently and negatively associated with reductions in roadside and midblock crashes. Wider shoulders were found to increase roadside and midblock crashes, while unpaved fixed-object offsets had a mixed safety effect by decreasing roadside crashes but having a slightly positive effect on midblock crashes. To understand better the reasons for these findings, this study then examined roadside crash site locations for tree and utility pole crashes. It found that the majority (between 65% and 83%) did not involve random midblock encroachments, as currently assumed, but instead involved objects located behind both driveways and side streets along higher-speed urban arterials. Collectively, these findings suggest that most urban roadside crashes are not the result of random error but are instead systematically encoded into the design of the roadway. The study concluded by distinguishing between random and systematic driver errors and by discussing strategies for eliminating systematic error while minimizing the consequences of random error.
Recycling of Laboratory-Prepared Reclaimed Asphalt Pavement Mixtures Containing Crumb Rubber–Modified Binders in Hot-Mix Asphalt
Authors: Shen Junan , Amirkhanian Serji , Lee Soon-Jae , Putman Brad
Published: May 2018

The recycling of reclaimed asphalt pavements (RAP) containing crumb rubber–modified binder is an important issue because some of these types of pavements are more than 10 to 15 years old in some areas in the United States. In this study, a laboratory investigation was conducted on the possibility of laboratory-prepared crumb rubber–modified RAP being recycled in Superpave® mixtures according to a normal recycling practice. Six mixtures (three recycled mixtures containing laboratory-prepared crumb rubber–modified RAP and three control virgin mixtures) were designed and tested. Three types of aggregates and two types of crumb rubber–modified binders were used for the mixtures. The crumb rubber–modified RAP used in the study was artificially aged in the laboratory with an accelerated aging process. The percentage of the RAP incorporated into the recycled mixtures was 15%. Evaluation of all mixtures included the following testing procedures: indirect tensile strength, asphalt pavement analyzer, and resilient modulus and gel permeation chromatography. Results from this study showed that ( a) it is possible to incorporate 15% crumb rubber–modified RAP into hot-mix asphalt using normal recycling practices and ( b) there is no significant difference between the three virgin and the three recycled mixtures in the properties discussed.
Spatial Demand Decisions in the Pacific Northwest
Authors: Train Kenneth , Wilson Wesley W.
Published: May 2018

Individual transportation demand decisions form the basis of aggregated demand models that the U.S. Army Corps of Engineers (ACE) uses to evaluate infrastructure improvements. The treatment by ACE planning models has been criticized on the grounds that the demand expressions are inappropriate. Specifically, the demand models used are perfectly inelastic (to a threshold point) and ignore the spatial market setting in which transportation decisions are made. This paper reports the results of a survey of shippers located on and off the Columbia–Snake waterway in the Pacific Northwest to estimate shipper-level demand decisions. The model addresses the concerns about the current ACE planning models by estimating elasticities rather than assuming them and by allowing the probability of using the river to be explained in terms of the spatial setting of the demander. The survey provides choices made in both revealed and stated preference settings. The choice attributes are rate, transit times, and reliability. The revealed and stated preference data are combined to estimate demand functions. The choice model is then used to simulate the likelihood of using the river as a function of shipment distances. To perform these simulations, rates and transit times are fit to distances. These relations are used with the choice model to explain decisions to use truck–barge as a function of distance to the waterway. The choice model provides statistically significant effects of rate, time, and reliability on mode choice, and the simulation suggests that as distance from the waterway increases, the likelihood of using the waterway falls.
The Ecological Footprint of Ports
Authors: Carrera-Gómez Gema , Coto-Millán Pablo , Doménech Juan Luis , Inglada Vicente , González Miguel Angel Pesquera , Castanedo-Galán Juan
Published: May 2018

The ecological footprint is studied as a macroindicator of sustainability applicable to companies and corporations. Until now, this macroindicator has been applied to cities, regions, or countries. It accounts for the consumption of natural resources by converting them into hectares of “nature” or consumed productive land. The parameters analyzed in this research have been consumption of energy, fuel, material, paper, wood, water, built land, and green areas, and residues generated by the Gijón Port Authority, Spain. The results show a net ecological footprint of 3,279.84 ha. The main components of the footprint are construction works (nearly 2,000 ha) and electricity consumption (679 ha). Studies of this kind enable companies to design sustainable development plans to reduce consumption as well as develop “green” (footprint-free) products and create “natural capital” (wastage absorption). Until now, these issues have not been on the agenda of companies, but they are indispensable in achieving real sustainability.
Selectorecombinative Genetic Algorithm to Relax Computational Complexity of Discrete Network Design Problem
Authors: Jeon Kyunghwi , Lee Jong Sung , Ukkusuri Satish , Waller S. Travis
Published: May 2018

A new approach is proposed for relaxing the computational complexity of the user equilibrium discrete network design problem (UE-DNDP), under deterministic traffic conditions, with a solution search procedure based on the selectorecombinative genetic algorithm (SGA). The SGA uses only selection and recombination operators rather than mutation. The UE-DNDP approach proposed in this study has a bilevel structure: the upper-level problem relates to the strategy of the network design authority, and the lower-level problem deals with network user behaviors. To solve the upper-level problem, the SGA is first used to create feasible network design solutions to the UE-DNDP by accounting for a budget constraint. Then the design authority selects the best network design strategy with minimum total system travel time (TSTT). Extensive experimental design and testing on GA operators and parameters are conducted to select the useful GA operators and parameters. For the lower-level problem, the best K-value concept is introduced to reduce the computational effort by allowing only a few best K-design solutions with best fitness values among the feasible network design solutions to the UE network evaluation model. The study uses statistical analysis to validate whether the proposed SGA-based UE-DNDP model is working well. The results of numerical analysis have shown that the proposed solution search procedure could significantly improve computational efficiency without loss of solution quality in terms of TSTT.
Modeling Impact of Technological Changes on Urban Commercial Trips by Commercial Activity Routing Type
Authors: Figliozzi Miguel Andres
Published: May 2018

Several noteworthy developments in logistics practice have taken place without an equivalent and comprehensive development in urban freight transportation modeling. Part of the problem is the lack of deep understanding of the workings of distribution processes in relation to the generation of truck traffic. This study emphasizes the role and importance that distribution network size and information and communications technology have on the truck traffic flows that materialize as the supply chain flows over the public infrastructure. A concept is developed of commercial activity routing types that characterize the interplay between transportation demand requests and routing characteristics. This research contributes to the field by proposing a novel and detailed characterization of truck flows in a supply chain context. With well-known, yet simple, models and formulas from vehicle routing, operations research, and management science literature, behavioral insights are derived about distributors’ and carriers’ routing and order-sizing decisions, since routing constraints and second-order effects are important drivers of truck flows. The main contribution is to bring a new commercial activity-routing perspective and a deeper level of operational decision-making analysis to cope with the intricacies of freight transportation modeling.
Noniterative Approach to Dynamic Traffic Origin–Destination Estimation with Parallel Evolutionary Algorithms
Authors: Kattan Lina , Abdulhai Baher
Published: May 2018

This study focuses on updating time-varying demand matrices by using real observation counts from advanced traffic management surveillance systems. A machine-learning technique using advanced evolutionary algorithms (EAs) is developed instead of the more conventional approaches in the literature. This EA-based demand estimation framework is implemented into a model called the Dynamic Origin–Destination (O-D) Estimator (DynODE). The potential of EAs in the dynamic O-D estimation problem lies in their powerful global search and optimization capabilities. DynODE is integrated with an existing dynamic traffic assignment platform (e.g., DYNASMART-P). The EA-based methods in this study are further augmented with EA parallelization to improve the quality and efficiency of the solution. DynODE mainly addresses offline O-D estimation problems. However, online O-D estimation can be achieved with the parallel version of DynODE with sufficient multiprocessing and parallel computing. The developed approach is rigorously evaluated on a medium-sized real network to assess the effects of various parallel structures. For all experiments, savings in computation resources as well as enhancement in the quality of solution were realized.
Real-Time Mass Passenger Transport Network Optimization Problems
Authors: Pagès Laia , Jayakrishnan R. , Cortés Cristián E.
Published: May 2018

The aim of the real-time mass transport vehicle routing problem (MTVRP) is to find a solution to route n vehicles in real time to pick up and deliver m passengers. This problem is described in the context of flexible large-scale mass transportation options that use new technologies for communication among passengers and vehicles. This study does not focus on the technological aspects required to operate this kind of system but instead treats the theoretical approaches to provide a consistent mathematical formulation of the problem and its solution. This analytical effort is relevant to future transportation options involving large-scale real-time routing of shared-ride fleet transit vehicles. However, the global optimization of a complex system involving routing and scheduling multiple vehicles and passengers as well as design issues has not been specifically studied in the past. This research proposes a methodology to solve it by means of a three-level hierarchical optimization approach. Within the optimization process, a mass transport network design problem (MTNDP) is solved. The MTVRP is introduced and a scheme to solve it is presented. Then the associated algorithm to perform the MTNDP optimization is described in detail. A real-world application is solved for the MTNDP, showing promising results with regard to the applicability of the methodology for large-scale transit problems.
Effect of Time Gaps and Lane Flow Distributions on Freeway Bottleneck Capacity
Authors: Banks James H.
Published: May 2018

An alternative to the current approach to freeway bottleneck capacity analysis is outlined: average time gaps (average time separations between the rear of a vehicle and the front of one following it), average passage times (average times for vehicles to pass a point), and lane flow distributions serve as intervening variables to link geometric, vehicle population, and driver population characteristics to capacity flows. The first phase of research to evaluate this approach is described. The goal was to investigate interrelationships between the intervening variables and to relate them to average flow per lane under capacity conditions. Two types of “capacity condition”–-pre-queue flow and queue discharge flow–-were considered. Traffic data for 18 extended data collection periods at 15 bottlenecks in the Minneapolis–St. Paul, Minnesota; San Diego, California; and Seattle, Washington, areas were analyzed to calculate average values of critical lane time gaps (where the critical lane is that with the highest flow rate), critical lane passage times, and critical lane flow ratios (ratio of critical lane flow to flow per lane) and to relate them to average flows for periods of pre-queue and queue discharge flow. Critical lane average time gaps were not significantly correlated with critical lane flow ratios but were significantly correlated with average passage times and with flow per lane in both pre-queue and queue discharge flow; however, critical lane flow ratios were significantly correlated with flow per lane in queue discharge flow only. There is a strong, near-linear negative relationship between critical lane flows and critical lane average time gaps in both pre-queue and queue discharge flow.
Reproducibility of Flow–Density Relations in Heavily Congested Flow Based on Individual Vehicle Data
Authors: Kim Youngho , Hall Fred L.
Published: May 2018

The flow-density relations represent equilibrium relations between flow and density in the stationary state. Using individual vehicle data, this paper extends to heavily congested flow the reproducibility of the flow-density relations found by Cassidy. A new filtering method using standard deviations of traffic variables in a vehicle group built from individual vehicle data is proposed to distinguish the nearly stationary state from the nonstationary state. The traffic data collected from the nearly stationary state with this filtering method show significantly smaller data scattering than do those without filtering in heavily congested flow, even though the data aggregation interval is kept at the same level. This fact indicates that a reproducible flow-density relation also exists in heavily congested flow if the traffic data are collected in the nearly stationary state
Time-Dependent Analysis of Density Fluctuations and Breakdown Thresholds on Congested Freeways
Authors: Bassan Shy , Polus Abishai , Faghri Ardeshir
Published: May 2018

Considerable congestion may develop on urban and suburban freeways during peak day periods, especially when traffic demand is high. Traffic breakdown is identified when there is a steep rise in density levels and a simultaneous rapid drop in speeds during the phase transition from dense congested stable (DCS) flow to breakdown flow. The purpose of this study was to generate breakdown thresholds by modeling the process of freeway flow breakdown. This paper uses the mathematical property of log periodic oscillations (LPO) to model the traffic density over time. The LPO process has been suggested in the past for modeling stock market crashes and the occurrence of large earthquakes, but this is the first time it has been proposed for freeway breakdown modeling. The calibration results obtained threshold values of densities and corresponding speeds, which trigger the breakdown process. The critical point has been identified as the maximum density rate of change during the first cycle that follows the DCS flow regime. The resulting density thresholds are comparatively higher than the equal density line thresholds proposed by the Highway Capacity Manual (HCM) between levels of service E and F. The use of Athol's conversion factor between occupancy and density has a major impact on this finding, and further examination has shown a good match between the LPO and HCM density thresholds.
New Hours-of-Service Rules
Authors: Dick Virginia , Hendrix James , Knipling Ronald R.
Published: May 2018

This paper presents a comprehensive, multidimensional evaluation of the federal interstate commercial driving hours-of-service (HOS) rules implemented on January 4, 2004. The study analyzes changes in fleet crash rates following the rule change and reactions of industry personnel (drivers and fleet safety managers) to the new rules. Information on industry personnel reaction to the new HOS rules was assessed through focus groups and a survey of nearly 1,000 drivers. In general, industry personnel like the new rules. Pluralities of drivers say that driving is easier and they are less fatigued. Drivers and companies like the 34-h restart but do not like the 14-h daily restriction on tour-of-duty duration. The study also gathered and aggregated 2003 and 2004 data from 23 mostly medium to large trucking fleets on vehicle mileage, DOT-reportable collisions, and driver injuries. Altogether, these 23 fleets traveled more than 10 billion miles annually in 2004 and represented approximately 8% of all large-truck mileage in the United States. This aggregated, “within subjects” comparison of HOS-related fleet safety and health data is the largest such compilation ever performed in the United States. Aggregated statistics for the 23 fleets showed statistically significant decreases in rates of collision (–3.7%) and preventable collision (–4.7%). There were even greater reductions in rates of driver injury (–12.6%) and driver collision-related injury (–7.6%). Taken together, these findings document that the trucking industry reaction has generally been favorable to the new HOS rules and that implementation of the new rules has been accompanied by a reduction in collision and injury rates.
Performance-Based Oversize and Overweight Permitting System
Authors: Fekpe Edward , Gopalakrishna Deepak , Woodrooffe John
Published: May 2018

This paper presents a conceptual framework for a federally supervised, state-administered, performance-based oversize and overweight permit program for the operation of heavier and larger vehicles on the public highways. The structure of the permitting system is based on experiences and practices in implementing performance-based systems in Australia, Canada, New Zealand, and the United States. Conceptually, the framework consists of three main interrelated components: administrative, enforcement, and evaluation systems. The administrative-system comprises several elements directed at establishing the requirements, standards, and administration of the permitting system. The enforcement system includes regulations, special conditions, education or communication to the industry, effective fines or penalties for violators, and adjudication. The enforcement system will periodically generate records indicating carrier compliance or noncompliance with the terms and conditions of permits and the frequency of these events. The evaluation system defines the data and processes to ensure that the permitting system is continuously evaluated. The results of the evaluation are necessary for revising the performance standards, limits, and conditions for the permitted vehicles. The challenge is enforcement of the performance-based, oversize and overweight permitting system. Periodic reassessments of permitted vehicles in addition to continued roadside enforcement of operating conditions are recommended.
Implementation of Spring Load Restrictions Using a Deflection-Calibrated Thaw Index
Authors: Goodman Stephen N.
Published: May 2018

The City of Ottawa, Canada, uses a Dynaflect to monitor the change in pavement strength during the spring thaw at 11 test sites selected to represent its arterial road network. As the average deflection of the sites approaches a threshold value, load restrictions are publicized by signage and advertisements in local newspapers. The restrictions remain in effect until deflections decrease below the threshold value. Local police equipped with portable weigh scales enforce the restrictions. The goal is to allow for the shortest possible restriction period and still ensure that the road infrastructure is protected. However, the decision to implement load restrictions is traditionally made too late, because prediction of thaw progression between weekly deflection testing is difficult. The city's pavements are occasionally subjected to full-load hauling during the initial and most critical portion of the thaw period. To predict the onset and progression of the spring thaw better, the thaw index (TI) was used in addition to deflection testing. The TI (as calibrated separately by the Minnesota Department of Transportation and Manitoba Transportation and Government Services, Canada) was analyzed to determine whether it would predict the same implementation date as did deflection data. Results suggested that calibration factors provided by either agency are sufficiently accurate in the Ottawa environment but the Manitoba calibration is slightly more precise. Future investigation will involve use of surface curvature index, as well as direct temperature measurements from the city's Road Weather Information Systems.
Estimating Thermal Conductivity of Pavement Granular Materials and Subgrade Soils
Authors: Côté Jean , Konrad Jean-Marie
Published: May 2018

The thermal conductivity of soils and granular materials is one of the most important parameters for frost action and thermal analyses in pavements and civil engineering infrastructures. Many predictive models were developed in past decades to correlate thermal conductivity of soils to basic soil index properties. Recently, relationships that cover the complete range of saturation in unfrozen and frozen states were established to consider the effects of porosity, geologic origin and mineralogy, soil type, particle type, and unfrozen water for a variety of soils. A simple and practical tool was developed to estimate thermal conductivity of pavement granular materials and subgrade soils directly as a function of the degree of saturation (water content) on the basis of these generalized thermal conductivity relationships. A new thermal conductivity equation is proposed to estimate thermal conductivity functions for soils such as well-graded gravels; coarse, medium, and fine sands; silty and clayey soils, and peat in unfrozen and frozen states. The new equation was successfully used to predict thermal conductivity functions of four different types of unfrozen and frozen soils from the literature (gravel, sand, clay, and peat). A set of charts is proposed to assess thermal conductivity of soils readily. The use of these charts is illustrated with examples. Both numerical and graphical estimating methods proved to provide accurate prediction results for thermal conductivities for soils and construction materials.
Hauling with Full Axle Weights and Reduced Tire Pressures on Weight-Restricted Roads in British Columbia
Authors: Bradley Allan H.
Published: May 2018

In North America, imposition of seasonal weight restrictions on thaw-weakened secondary roads may interrupt transport of raw materials to processing facilities for 6 to 12 weeks or even longer. This annual disruption forces processing facilities to operate from stockpiled inventory and typically results in large extra costs for both the processing facility and trucks. The Forest Engineering Research Institute of Canada (FERIC) has been investigating the potential for shortening the weight restriction period (i.e., lengthening the period for hauling with full, legal weights) on secondary roads by hauling with road-friendly trucks. FERIC developed a modeling process to estimate when fully loaded trucks equipped with road-friendly technologies, such as multiple axle groups, large tires, or tire pressure control systems (TPCS), could resume hauling on thaw-weakened pavements without accelerating pavement damage. From 2000 to 2003, FERIC used this modeling process to conduct full-scale tests on a variety of thin pavements in British Columbia, Canada. During these tests, fully loaded log trucks were able to haul during the last 3 to 5 weeks of the weight restriction period with no measurable increase in pavement rutting or cracking. In 2004, the British Columbia Ministry of Transportation introduced a program to exempt trucks operating with TPCS from seasonal weight restrictions on approved roads in British Columbia. FERIC, in cooperation with several forest companies, conducted operational hauling under the new program in spring 2004 and 2005. The operations experienced from 2 to 8 weeks extra hauling during the weight restriction period, with no acceleration of road damage.