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This study explores speed choice behavior of travelers under realistic and fabricated Dynamic Message Signs (DMS) content. Using web-based survey information of 4,302 participants collected by Amazon Mechanical Turk in the United States, we develop a set of multivariate latent-based ordered probit models participants. Results show female, African-Americans, drivers with a disability, elderly, and drivers who trust DMS are likely to comply with the fabricated messages. Drivers who comply with traffic regulations, have a good driving record, and live in rural areas, as well as female drivers are likely to slow down under fabricated messages. We highlight that calling or texting, taking picture, and tuning the radio are distracting activities leading drivers to slow down or stop under fictitious scenarios. [ABSTRACT FROM AUTHOR]

Highway-rail grade crossing (HRGC) crashes continue to be the major contributors to rail causalities in the United States and have been intensively researched in the past. Data-mining models focus on prediction while dominant general linear models focus on model and data fitness. Decision makers and traffic engineers rely on prediction models to examine at-grade crash frequency and make safety improvement. The gradient boosting (GB) model has gained popularity in many research areas. In this study, to fully understand the model performance on HRGC accident prediction performance, the GB model with functional gradient descent algorithm is selected to analyze crashes at highway-rail grade crossings (HRGCs) and to identify contributor factors. Moreover, contributors' importance and partial-dependent relations are generated to further understand the relationship of identified contributors and HRGC crash likelihood to concur "black box" issues that most machine learning methods face. Furthermore, to fully demonstrate the model's prediction performance, a comprehensive model prediction power assessment based on six measurements is conducted, and the prediction performance of the GB model is verified and compared with a decision tree model as a reference due to their popularity and comparable data availability. It is demonstrated that the GB model produces better prediction accuracy and reveals nonlinear relationships among contributors and crash likelihood. In general, HRGC crash likelihood is significantly impacted by several traffic exposure factors: highway traffic volume, railway traffic volume, and train travel speed and others. [ABSTRACT FROM AUTHOR]

Traffic congestion is one key factor that delays emergency supply logistics after disasters, but it is seldom explicitly considered in previous emergency supply planning models. To fill the gap, we incorporate traffic congestion effects and propose a two-stage location-allocation model that facilitates the planning of emergency supplies pre-positioning and post-disaster transportation. The formulated mixed-integer nonlinear programming model is solved by applying the generalized Benders decomposition algorithm, and the suggested approach outperforms the direct solving strategy. With a case study on a hurricane threat in the southeastern USA, we illustrate that our traffic congestion incorporated model is a meaningful generalization of a previous emergency supply planning model in the literature. Finally, managerial insights about the supplies pre-positioning plan and traffic control policy are discussed. [ABSTRACT FROM AUTHOR]

Abstract The Manual on Uniform Traffic Control Devices (MUTCD) for Streets and Highways recommends hill signs be placed in advance of downgrade descent of mountain passes. Mountain passes increase the risk of a runaway, or out of control trucks and so the advance warning signs inform the driver to take special precautions such as reducing speed or using lower gears during the descent. The Wyoming Department of Transportation has installed steep grade advance warning systems on Wyoming mountain passes. However, concerns for out of control trucks on the mountain passes persist. The objective of this study is to evaluate the safety effectiveness of steep grade advance warning signs for trucks on Wyoming mountain passes. The safety evaluation was carried out by implementing a zero-inflated negative binomial modeling technique for predicting truck crashes on mountain passes. The outcome was two models that showed the risk of runaway truck accidents were high at locations where either the grades were steep and long or the grades were long with multiple vertical curves. The analysis showed the current advance warning systems were not significantly impacting truck crash risks at the high risk locations. The study, therefore, recommends some improvements to the current advanced warning signs or implementing an improved Federal Highway Administration Grade Severity Rating System based warning system that will significantly improve truck safety at the hazardous locations. The study informs policy makers on the safety issues on Wyoming Mountain passes with regards to runaway trucks and makes recommendations for reducing the risk of runaway truck crashes on mountain passes. [ABSTRACT FROM AUTHOR]

The European Union project of Single European Sky initiated a reorganization of European airspace and proposed additional measures for air traffic management to achieve the key objectives of improving efficiency and capacity while at the same time enhancing safety. The concept of multiple remote tower operation is that air traffic controllers (ATCOs) can control several airfields from a distant virtual control centre. The control of multiple airfields can be centralised to a virtual centre permitting the more efficient use of ATCO resources. This research was sponsored by the Single European Sky ATM Research Program and the ATM Operations Division of the Irish Aviation Authority. A safety case was developed for migration of multiple remote tower services to live operations. This research conducted 50 large scale demonstration trials of remote tower operations from single tower operations to multiple tower operations for safety assessment by air navigation safety regulators in 2016. A dedicated team of air traffic controllers and technology experts successfully completed the safety assessment of multiple remote tower operations in real time. The implementation of this innovative technology requires a careful balance between cost-efficiency and the safety of the air traffic control in terms of capacity and human performance. The live trial exercises demonstrated that the air traffic services provided by the remote tower for a single airport and two medium airports by a single ATCO with ‘in sequence’ and ‘simultaneous’ aircraft operation was at least as safe as provided by the local towers at Cork and Shannon aerodromes. No safety occurrence was reported nor did any operational safety issue arise during the conduct of the fifty live trial exercises. [ABSTRACT FROM AUTHOR]

This article studies a capacitated fixed-charge multiperiod location–transportation problem in which, while the location and capacity of each facility must be determined immediately, the determination of the final production and distribution of products can be delayed until actual orders are received in each period. In contexts where little is known about future demand, robust optimization, namely using a budgeted uncertainty set, becomes a natural method for identifying meaningful decisions. Unfortunately, it is well known that these types of multiperiod robust decision problems are computationally intractable. To overcome this difficulty, we propose a set of tractable conservative approximations for the problem that each exploit to a different extent the idea of reducing the flexibility of the delayed decisions. While all of these approximation models outperform previous approximation models that have been proposed for this problem, each also has the potential to reach a different level of compromise between efficiency of resolution and quality of the solution. A row generation algorithm is also presented to address problem instances of realistic size. We also demonstrate that full flexibility is often unnecessary to reach nearly, or even exact, optimal robust locations and capacities for the facilities. Finally, we illustrate our findings with an extensive numerical study where we evaluate the effect of the amount of uncertainty on the performance and structure of each approximate solution that can be obtain d. [ABSTRACT FROM AUTHOR]

We study an emergency response network design problem that integrates relief (supply) and evacuation (demand) sides under disaster location and intensity uncertainties which, in turn, dictate uncertainty in terms of the location and amount of demand. Representing these uncertainties by discrete scenarios, we present a stochastic programming framework in which two second stage objectives, the average and worst case costs, are combined. In our model, we minimize, over all of the scenarios, the fixed costs of opening supply centers and shelters, and the weighted sum of average and worst case flow costs. Thus, the model gives the decision maker the flexibility to put relative emphasis on the worst case and average flow cost minimization and explore outcomes in terms of total costs and network configurations. To solve large scale instances with varying relative weights, we devise alternative Benders Decomposition approaches. We implement these by using an advanced callback feature of the solver while simultaneously incorporating several performance-enhancing steps that help to improve runtimes significantly. We conduct a detailed computational study to highlight the efficiency of our proposed solution methodology. Furthermore, we apply our approach in a realistic case study based on Geographical Information Systems data on coastal Texas and present interesting insights about the problem and the resulting network structures for varying weights assigned to objectives. [ABSTRACT FROM AUTHOR]

Autonomous Vehicle (AV) technology is quickly becoming a reality on US roads. Testing on public roads is currently undergoing, with many AV makers located and testing in Silicon Valley, California. The California Department of Motor Vehicles (CA DMV) currently mandates that any vehicle tested on California public roads be retrofitted to account for a back-up human driver, and that data related to disengagements of the AV technology be publicly available. Disengagements data is analyzed in this work, given the safety-critical role of AV disengagements, which require the control of the vehicle to be handed back to the human driver in a safe and timely manner. This study provides a comprehensive overview of the fragmented data obtained from AV manufacturers testing on California public roads from 2014 to 2017. Trends of disengagement reporting, associated frequencies, average mileage driven before failure, and an analysis of triggers and contributory factors are here presented. The analysis of the disengagements data also highlights several shortcomings of the current regulations. The results presented thus constitute an important starting point for improvements on the current drafts of the testing and deployment regulations for autonomous vehicles on public roads. [ABSTRACT FROM AUTHOR]

This is the sixth in a series of reviews of research on graduated driver licensing (GDL) published in the Journal of Safety Research , the present review covering the period mid-2012 through 2016. In the two decades since GDL programs began to be introduced on a widespread basis in the United States, a vast amount of research has been published. The current review discusses recent research and the present state of knowledge on the following topics: characteristics of the novice driver population; effects of GDL on crashes for ages 16–19; the learner and intermediate periods; night and passenger restrictions; cellphone laws; GDL for older novices; enforcement of GDL rules; and programs attempting to influence GDL compliance and safe driving practices in general. GDL stands out as a successful policy for reducing teen driver crashes and is worth building on to extend its benefits. Strengthening existing GDL programs has the most potential for producing further crash reductions. [ABSTRACT FROM AUTHOR]

Urban transportation systems are vulnerable to congestion, accidents, weather, special events, and other costly delays. Whereas typical policy responses prioritize reduction of delays under normal conditions to improve the efficiency of urban road systems, analytic support for investments that improve resilience (defined as system recovery from additional disruptions) is still scarce. In this effort, we represent paved roads as a transportation network by mapping intersections to nodes and road segments between the intersections to links. We built road networks for 40 of the urban areas defined by the U.S. Census Bureau. We developed and calibrated a model to evaluate traffic delays using link loads. The loads may be regarded as traffic-based centrality measures, estimating the number of individuals using corresponding road segments. Efficiency was estimated as the average annual delay per peak-period auto commuter, and modeled results were found to be close to observed data, with the notable exception of New York City. Resilience was estimated as the change in efficiency resulting from roadway disruptions and was found to vary between cities, with increased delays due to a 5% random loss of road linkages ranging from 9.5% in Los Angeles to 56.0% in San Francisco. The results demonstrate that many urban road systems that operate inefficiently under normal conditions are nevertheless resilient to disruption, whereas some more efficient cities are more fragile. The implication is that resilience, not just efficiency, should be considered explicitly in roadway project selection and justify investment opportunities related to disaster and other disruptions. [ABSTRACT FROM AUTHOR]

Over the past three decades, urban congestion has become more costly in terms of time, money, and fuel. For the top 101 largest US urban centers, congestion generated 4.8 billion hours of travel delays in 2011, up from 1.1 billion hours in 1982. Congestion also required 8.419 million cubic meters of excess fuel consumption in 2011, up from 1.73 million cubic meters in 1982. Finally, the excess CO 2 emitted from congestion amounted to 19.524 billion kilograms in 2011, up from 3.94 billion kilograms in 1982. We examined the scaling relationships between the population sizes of urban centers and traffic congestion for four subgroups of urban centers with varying population sizes. We found that scaling relationships were superlinear for most subgroups. However, for the subgroup comprising mega cities with populations of over 3 million people, the relationship was linear. The varying scaling relationships we found for cities with different population sizes may resolve the contradictory scaling results reported in the extant literature. Several other implications from our findings are also discussed. [ABSTRACT FROM AUTHOR]

The article examines challenges facing regional transportation planners in the U.S. in an era characterized by uneven growth and accelerating impacts of climate change. Topics discussed include ways in which growing inequality and technological change affect the priorities for transportation planning; and metropolitan transportation systems in New York region.

The article highlights the role of traffic enforcement, analyzes its efficacy to deter dangerous driving, and suggests a new framework for traffic enforcement suited to the goals of Vision Zero. It suggests that primary goal of Vision Zero-related traffic enforcement must be to create long-lasting deterrence of dangerous driving behavior.

Problem, research strategy, and findings: Planners commonly recommend compact development in part as a way of getting people to drive less, with the idea that less driving will lead to more sustainable communities. Planners base their recommendations on a substantial body of research that examines the impact of compact development on driving. Different studies, however, have found different outcomes: Some studies find that compact development causes people to drive less, while other studies do not. I use meta-regression analysis to a) explain why different studies on driving and compact development yield different results, and b) combine different findings from many studies into reliable statistics that can better inform planning practice. I address the following questions: Does compact development make people drive less, and if so, how much less? I find that compact development does make people drive less, because most of the compact development features I study have a statistically significant negative influence on driving. The impact, however, is fairly small: Compact development features do not appear to have much influence on driving. My findings are limited to some extent because they are derived from small sample sizes. Takeaway for practice: Planners should not rely on compact development as their only strategy for reducing driving unless their goals for reduced driving are very modest and can be achieved at a low cost. [ABSTRACT FROM PUBLISHER]

The purpose of this study is to provide a geographical and multi-criteria vulnerability assessment method to quantify the impacts of extreme earthquakes on road networks. The method is applied to two US cities, Los Angeles and San Francisco, both of which are susceptible to severe seismic activities. Aided by the recent proliferation of data and the wide adoption of Geography Information Systems (GIS), we use a data-driven approach using USGS ShakeMaps to determine vulnerable locations in road networks. To simulate the extreme earthquake, we remove road sections within “very strong” intensities provided by USGS. Subsequently, we measure vulnerability as a percentage drop in four families of metrics: overall properties (length of remaining system); topological indicators (betweenness centrality); accessibility; and travel demand using Longitudinal Employment Household Dynamics (LEHD) data. The various metrics are then plotted on a Vulnerability Surface (VS), from which the area can be assimilated to an overall vulnerability indicator. This VS approach offers a simple and pertinent method to capture the impacts of extreme earthquake. It can also be useful to planners to assess the robustness of various alternative scenarios in their plans to ensure that cities located in seismic areas are better prepared to face severe earthquakes. [ABSTRACT FROM AUTHOR]

This study characterizes navigation conflicts in a region with a large traffic volume along the United States (US) Atlantic Coast, using an empirical approach that analyzes Automated Identification System (AIS) data for a full year (2010). The region includes areas proposed for wind energy development, and this characterization of vessel conflicts could be useful as a baseline to evaluating the effect of offshore wind areas on navigation conflicts and vessel collisions. There have been no collisions reported within the study area. This study analyzes the one year of AIS data to obtain vessel tracks and makes simultaneous pairwise comparisons to determine the number and rate of vessel encounters and near-misses (navigation conflicts). For vessel pairs in an encounter (3 nm distance; crossing, head-on, overtaking), a 'blind vessel' assumption was used to calculate the number of potential near misses and potential collisions. Graphical analysis of the frequency of vessels involved in potential near misses produced vessel response curves that provided the time of peak frequencies prior to the time of closest approach for each encounter type. These peak times were up to 600 s prior to the time of closest approach. The analyses of potential near misses and collision used the data during the period between the time of peak frequency and the time of closest approach to filter the data used in the calculation of the probability of potential collisions. The period included collsion avoidance maneuvering. Statistical analyses are made to estimate the point values and uncertainty of near miss rates and the probability of potential collisions for each type of encounter from which bounding estimates of the collision rates are made. These bounding collision rates are found to be comparable with estimates from previous studies. Causation probabilities were also estimated and compared with previous studies. The response curves may also have utility in the simulation of navigation conflicts. The use of surrogate data to evaluate the effect of wind energy areas is considered, though their usefulness depends on comparability of traffic density and the level and type of traffic control systems implemented. • Evaluates the occurrence of encounters and near-misses along the US Atlantic Coast that include proposed wind energy areas. • Examines the overall vessel responses to potential near-misses. • Estimates the bounding rate collisions and causation probabilities in the analysis domain. • Discusses the possible impacts of the presence of wind energy areas on collision rates. [ABSTRACT FROM AUTHOR]

Approximately 11% of bridges in the United States are categorized as structurally deficient and there is a marked need of more accurately evaluating true structural capacity. Structural Health Monitoring (SHM) systems can provide a timely indication of the need for maintenance, repair, rehabilitation and replacement of bridges and can greatly improve the apportionment and management of limited resources. This paper presents an Automated Ambient Traffic (AAT) approach for determining load rating of bridges monitored by the BECAS SHM system under ambient traffic. The AAT approach was developed through a process integration of truck detection, bridge model calibration, and bridge load rating: (1) the quasi-static bridge strain response and the characteristics of associated trucks are collected; (2) multiple trucks are randomly sampled from a historic Weigh-In-Motion (WIM) database; and (3) for each combination of strain response and truck selection, an Finite Element (FE) model is calibrated and used to calculate a load rating. Sampling strategies were discussed for appropriately quantifying the influence of uncertainties of truck characteristics on the calibration and load rating results. To demonstrate this approach, a sample three-span, five-girder, and two-lane steel girder/concrete deck (I-80) bridge was utilized. A load rating of the I-80 Bridge using the Traditional Known Truck (TKT) approach was performed to provide benchmark results. The results of the calibration and load rating using the AAT approach were derived using three different sampling strategies and compared to those using the TKT approach. The sampling strategy, selecting strain response with a spectrum of higher peak girder strains, associated trucks with a spectrum of higher gross vehicle weights, and two truck events on south and north lanes respectively for a calibration, resulted in the best calibration and load rating results. It was concluded that the AAT approach using the BECAS SHM system is a reliable method for continuously estimating the load carrying capacity of bridges. [ABSTRACT FROM AUTHOR]

In this study, 20-year and 40-year designs of common pavement types in USA at three traffic levels are examined for their environmental burdens, including hot mix asphalt pavement, jointed plain concrete pavement and continuously reinforced concrete pavement. The study first introduced a previously built life cycle assessment model in pavement engineering and then performed the detailed modelling for each pavement design, with special efforts devoting to the delay estimation of in the congestion module and the usage module (roughness effect on the fuel economy). In the context of this study, regarding the multiple environmental indicators, it is found that 40-year pavement designs do not necessarily carry environmental advantages over their 20-year counterparts, being only possible at ‘high’ traffic volumes. Sensitivity analysis indicates that the influences of stress developing rate, recycling, feedstock energy of asphalt binder and maintenance strategy are less significant compared to that of traffic volume. In the life cycle inventory, material module and usage module are two dominating contributors; share of congestion module due to construction and maintenance activities grows quickly with the increase of traffic volume. [ABSTRACT FROM AUTHOR]

Many communities in the United States have been adding new light rail to bus-predominant public transit systems. However, there is disagreement as to whether opening light rail lines attracts new ridership or merely draws ridership from existing transit users. We study a new light rail line in Salt Lake City, Utah, USA, which is part of a complete street redevelopment. We utilize a pre-test post-test control group quasi-experimental design to test two different measures of ridership change. The first measure is calculated from stops along the light rail route; the second assumes that nearby bus stops might be displaced by the rail and calculates ridership change with those stops included as baseline. Both the simple measure (transit use changes on the complete street light rail corridor) and the “displacement” measure (transit use changes in the one-quarter mile catchment areas around new light rail stops) showed significant ( p <.01) and substantial (677%) increases in transit passengers compared to pre-light rail bus users. In particular, the displacement analysis discredits a common challenge that when a new light rail line opens, most passengers are simply former bus riders whose routes were canceled in favor of light rail. The study suggests that light rail services can attract additional ridership to public transit systems. In addition, although pre-post control-group designs require time and effort, this project underscores the benefits of such quasi-experimental designs in terms of the strength of the inferences that can be drawn about the impacts of new transit infrastructure and services. [ABSTRACT FROM AUTHOR]

To better understand the links between winter precipitation (snow, sleet, and freezing rain) and travel risk, data on weather conditions and vehicle crashes, injuries and fatalities are gathered for 13 U.S. cities. A matched pair analysis is used to construct event-control pairs to determine the relative risk of crash, injury, and fatality. Winter precipitation is associated with a 19% increase in traffic crashes and a 13% increase in injuries compared to dry conditions. The type of winter precipitation (snowfall vs. freezing rain, ice pellets, or sleet) had no significant impact on the relative risk of crash. The relative risk of crash was significantly higher during the evening (1800–2359 local time) than during other times of the day. More intense precipitation led to increased relative risk of crash and injury compared to less intense precipitation. Relative risk of crash, injury, or fatality was not significantly higher during the first three winter precipitation events of the year as compared to subsequent events. The relative risk of both winter precipitation crash and injury showed no significant trend during the 1998–2008 period. Sensitivity of U.S. cities to winter precipitation varies from city to city in a manner that is not easily explained. Future research will be required to determine which safety interventions are most effective in each city and revise or expand safety programs appropriately. [ABSTRACT FROM AUTHOR]

This study pools household travel and built environment data from 15 diverse US regions to produce travel models with more external validity than any to date. It uses a large number of consistently defined built environmental variables to predict five household travel outcomes – car trips, walk trips, bike trips, transit trips and vehicle miles travelled (VMT). It employs multilevel modelling to account for the dependence of households in the same region on shared regional characteristics and estimates ‘hurdle’ models to account for the excess number of zero values in the distributions of dependent variables such as household transit trips. It tests built environment variables for three different buffer widths around household locations to see which scale best explains travel behaviour. The resulting models are appropriate for post-processing outputs of conventional travel demand models, and for sketch planning applications in traffic impact analysis, climate action planning and health impact assessment. [ABSTRACT FROM AUTHOR]

This research considers the implications of building places that possess many of the qualities that make New Urbanism so desirable but also marginalizing them with other qualities that prioritize automobility to meet the demands of conventional traffic engineering standards. By examining the existing built environment of Stapleton – a New Urbanist development in Denver, Colorado – in terms of street network characteristics, street designs, and intersection designs, I investigate the inconsistencies of the resulting built environment with respect to the latest research and state-of-the-practice New Urbanism design ideals. The outcomes are then considered in terms of how people actually use the transportation system by way of vehicle speed studies and travel diaries. The trends suggest that mixing New Urbanist neighborhood and street design characteristics with conventional traffic engineering standards results in travel behaviors more consistent with conventional auto-oriented developments. [ABSTRACT FROM PUBLISHER]

Air travel has been a major transportation for commerce and tour in many countries. As the demand of air traffic has been increasing, air traffic management has confronted with poverty of handling the increase of the demand of runway facilities where congestion often takes place. In order to cope with such problems, runway efficiency enhancement or capacity increasing are taken into account. In air traffic management, the effective air space utilization and air control workload management can be improved by the use of many up-to-date technologies in forms of decision support tools. This study developed a computer-aided decision support model in the form of integer programming. The purpose of the model was to allocate airplanes arrival at U.S. Center-TRACON airspace to enter feeder gates and to design optimal routes along the track to runway. Results of optimal path of the airplanes throughout the TRACON air space system which yield a minimum delay were presented. [ABSTRACT FROM AUTHOR]

Trucks move around 70% of the freight weight in the United States. The combination of increased commercial motor vehicle traffic, tighter delivery schedules, and federally regulated limits on driving time lead to a nationally recognized problem on interstate highways in the United States, i.e., increased demand for commercial truck parking. Unavailability of sufficient parking spaces at rest areas results in illegal and unsafe parking at entrance/exit ramps, and other unauthorized areas. The research reported in this paper, funded by the Florida DOT, sought to understand the truck parking problem in Florida, determine the supply and demand characteristics for commercial truck parking, assess technology that can be used to improve parking management, and conduct a pilot project to test a smart truck parkingmanagement technology to make better utilization of commercial parking spaces at public rest areas. [ABSTRACT FROM AUTHOR]

Traffic safety, once neglected within the larger history of the automobile in the United States, has finally been getting the attention it always deserved. Nevertheless, historians still sometimes misappraise traffic safety in one era by the standards of another. A historical assumptions have contributed to misinterpretations--for example, that Americans of the 1920s were extraordinarily tolerant of traffic casualties because they did not respond to them as more recent traffic-safety paradigms would prescribe. As a corrective, four paradigms, approximately sequential, are proposed: Safety First, Control, Crashworthiness, and Responsibility. Historians are invited to borrow, modify, or replace them, and to consider their applicability to other countries. Whether these particular paradigms survive review or not, historians who are alert to safety paradigms will produce more reliable scholarship on the history of traffic safety. [ABSTRACT FROM AUTHOR]

Introduction Based on the Federal Railway Administration (FRA) database, approximately 62% of the collisions at highway-rail crossings occurred at locations with active controls (gate and flashing lights), followed by passive controls (cross bucks and stop signs) with approximately 28% of accidents. Method The study applied an ordered probit model to explore the determinants of driver injury severity under various control measures at highway-rail grade crossing in the United States. Results The analysis found that schedule factor (peak hour), visibility, motor vehicle speed, train speed, driver’s age, area type, traffic volume and highway pavement impact driver injury severity at both active and passive highway-rail crossings. Practical Applications For both active and passive control highway-rail grade crossings, speed control for both trains and vehicles will significantly reduce driver injury severity. However, the level of influence by vehicle speed and train speed at passive control is higher compared with active control. Paving highways at highway-rail grade crossings will also help to reduce driver injury severity at highway-rail crossing accidents. [ABSTRACT FROM AUTHOR]

The author offers a response to a commentary made by Professor Dan Subotnik on his article "The Emerging American Police State," published within the issue. He says that he wrote the article to address important issues of constitutional dimension. These issues include the relationship between traffic fines and race and ethnicity, and the impact of the proliferation of stop signs on the environment and the economy.

Hybrid electric vehicles (HEVs) are considered to be one of the energy-efficient technologies for near-term sustainability of the transportation sector. Over the years, research has focused on improving fuel economy (FE) for a given drive cycle, but FE variability over a realistic range of real-world driving patterns has been generally overlooked, and this can lead to FE benefits not being fully realized in real-world usage. No systematic methodology exists to reduce FE variability by design optimization of powertrain components. This study proposes a methodology of powertrain component optimization to reduce the FE variability due to variations in driving patterns. In the proposed methodology, powertrain components are optimum over a range of driving patterns of different traffic conditions and driving styles simultaneously. The proposed methodology demonstrates the potential to reduce FE variability by up to 34% over six driving patterns of different traffic conditions and driving styles. [ABSTRACT FROM PUBLISHER]

Empirical evidence suggests that most urban systems experience a transition from a monocentric to a polycentric organization as they grow and expand. We propose here a stochastic, out-of-equilibrium model of the city, which explains the appearance of subcenters as an effect of traffic congestion. We show that congestion triggers the instability of the monocentric regime and that the number of subcenters and the total commuting distance within a city scale sublinearly with its population, predictions that are in agreement with data gathered for around 9000 U.S. cities between 1994 and 2010. [ABSTRACT FROM AUTHOR]

In this study, we empirically investigate the impacts of urban road congestion and road capacity expansion on the competition between major container ports in the US. We find that more delays on urban roads may cause shippers to switch to competing rival ports: a 1% increase in road congestion delays around the port is associated with a 0.90–2.48% decrease in the port's container throughput but a 0.62–1.69% increase in the rival port's throughput. Adding local roads tends to benefit the port and harm its rival (in terms of throughput) by reducing road congestion. However, the overall impact of road provision on ports’ throughput varies among the sample ports, as road capacity expansion may affect ports’ output through channels other than road congestion delays. [ABSTRACT FROM AUTHOR]

Highlights: [•] The effect three recent trends in vehicle design had on US fatality risk is investigated. [•] Side airbags reduce risk in cars, but not trucks or CUVs/minivans, struck in the side. [•] Better alignment of truck bumpers reduces risk in their crash partners. [•] Neither is expected to change the current relationship between vehicle mass and risk. [•] Shifting light truck drivers into cars lowers risk more than large reductions in mass. [ABSTRACT FROM AUTHOR]

Abstract: The persistent infrastructure underinvestment coupled with a significant growth in commercial and non-commercial transportation demand has rendered the US transportation infrastructure unprepared for current and future demands. A significant improvement in the condition of the US transportation infrastructure must be grounded on a more sustainable and proactive approach to address the existing gap between short-term commitments and long-term needs. This paper demonstrates in quantitative terms the value of long-term investments to overcome the historical impediments to infrastructure rehabilitation, including the need for a proactive political structure that compensates for the apparent lack of public accountability, and for the poor understanding of the socio-economic effects caused by transportation infrastructure failures. Such a process could avoid impending catastrophes. This paper presents a modeling paradigm that accounts for multiple stakeholder perspectives and relates the formulation of public policy to a long-term horizon through the modeling of the transportation infrastructure as a system of systems. The methodology enables involved stakeholders and decision makers to visualize their shared interests and to promote coordinated individual decisions in order to achieve a more acceptable level of the overall system of systems objectives. To illustrate the relevance of the proposed modeling approach, we apply it to a bridge maintenance problem and we discuss the synthesis of existing engineering practice with socio-economic factors that aids in streamlining long-term infrastructure goals with immediate short-term needs. The insights obtained from the proposed system of systems methodological approach point to the need to adopt a more forward-looking and collaborative public policy for infrastructure maintenance. [Copyright &y& Elsevier]

Abstract: Motor vehicle crashes result in millions of injuries and thousands of deaths each year in the United States. While most crash research datasets use Abbreviated Injury Scale (AIS) codes to identify injuries, most hospital datasets use the International Classification of Diseases, version 9 (ICD-9) codes. The objective of this research was to establish a one-to-one mapping between AIS and ICD-9 codes for use with motor vehicle crash injury research. This paper presents results from investigating different mapping approaches using the most common AIS 2+ injuries from the National Automotive Sampling System-Crashworthiness Data System (NASS-CDS). The mapping approaches were generated from the National Trauma Data Bank (NTDB) (428,637 code pairs), ICDMAP (2500 code pairs), and the Crash Injury Research and Engineering Network (CIREN) (4125 code pairs). Each approach may pair given AIS code with more than one ICD-9 code (mean number of pairs per AIS code: NTDB=211, ICDMAP=7, CIREN=5), and some of the potential pairs are unrelated. The mappings were evaluated using two comparative metrics coupled with qualitative inspection by an expert physician. Based on the number of false mappings and correct pairs, the best mapping was derived from CIREN. AIS and ICD-9 codes in CIREN are both manually coded, leading to more proper mappings between the two. Using the mapping presented herein, data from crash and hospital datasets can be used together to better understand and prevent motor vehicle crash injuries in the future. [Copyright &y& Elsevier]

Abstract: Over the past twenty-five years, more workers in the United States have been given the option of flexible work schedules, which are designed to redistribute commuter traffic over the course of a day by allowing employees to vary their arrival and/or departure times. This paper examines whether and to what degree access to flexible work schedules affects the departure times of commuters in the two largest and most congested areas of California: the Los Angeles and San Francisco regions. Trip data were obtained from the 2009 US National Household Travel Survey (NHTS). The results of this study show that people who have access to flexitime preferred later departure times rather than earlier times. Workers with flexible schedules were 3.30% less likely to depart before peak hours, 4.11% less likely during peak hours, and 7.41% more likely afterwards. Based on these findings, government agencies and private firms in regions with severe traffic congestion problems may consider adopting alternative work schedules. [Copyright &y& Elsevier]

Abstract: Background: Recent concerns have been raised about the United States’ “Traffic Safety Culture.” While the “safety culture” construct has been studied in occupational settings, it appears that no assessments of national traffic safety culture have been published in the scientific literature. Purpose: To assess whether current public attitudes and behaviors support traffic safety advancement in the United States. Methods: A mail survey containing items that had been endorsed by traffic safety experts was fielded to a nationally representative sample of U.S. households in 2009. Completed surveys were returned by 46% of recipients. Results: Mean ratings indicated that respondents support a majority of the items that were developed to reflect positive Traffic Safety Culture. They “neither agreed nor disagreed,” however, with 43% of pro-safety statements. The item that was mostly highly rated by subjects suggested that “the whole key to road safety” lies in educating drivers. When items were grouped by topic, those which focused on the control of alcohol-impaired driving were most popular. Female respondents and older respondents demonstrated more support for traffic safety advancement. Conclusions: The U.S. public appears to be favorably disposed to traffic safety but their support is not uniform across topics or population subgroups. Their responses also suggest they may not know or like some of the evidence-based recommendations being promoted by traffic safety experts. Future research should explore the bases for public resistance to policies and practices that have been shown to save lives. [Copyright &y& Elsevier]

The Desert Research Institute conducted an on-road mobile source emission study at a traffic tunnel in Van Nuys, California, in August 2010 to measure fleet-averaged, fuel-based emission factors. The study also included remote sensing device (RSD) measurements by the University of Denver of 13,000 vehicles near the tunnel. The tunnel and RSD fleet-averaged emission factors were compared in blind fashion with the corresponding modeled factors calculated by ENVIRON International Corporation using U.S. Environmental Protection Agency's (EPA's) MOVES2010a (Motor Vehicle Emissions Simulator) and MOBILE6.2 mobile source emission models, and California Air Resources Board's (CARB's) EMFAC2007 (EMission FACtors) emission model. With some exceptions, the fleet-averaged tunnel, RSD, and modeled carbon monoxide (CO) and oxide of nitrogen (NOx) emission factors were in reasonable agreement (±25%). The nonmethane hydrocarbon (NMHC) emission factors (specifically the running evaporative emissions) predicted by MOVES were insensitive to ambient temperature as compared with the tunnel measurements and the MOBILE- and EMFAC-predicted emission factors, resulting in underestimation of the measured NMHC/NOxratios at higher ambient temperatures. Although predicted NMHC/NOxratios are in good agreement with the measured ratios during cooler sampling periods, the measured NMHC/NOxratios are 3.1, 1.7, and 1.4 times higher than those predicted by the MOVES, MOBILE, and EMFAC models, respectively, during high-temperature periods. Although the MOVES NOxemission factors were generally higher than the measured factors, most differences were not significant considering the variations in the modeled factors using alternative vehicle operating cycles to represent the driving conditions in the tunnel. The three models predicted large differences in NOxand particle emissions and in the relative contributions of diesel and gasoline vehicles to total NOxand particulate carbon (TC) emissions in the tunnel. [ABSTRACT FROM AUTHOR]

This paper presents an investigation into the current U.S. practice regarding the use of channelized right-turn lanes at signalized intersections, the type of traffic control used, and the safety experience of highway agencies. The study involved a literature review and a practice survey, which was distributed to all state and selected local agencies in the United States. The literature review revealed the overall lack of knowledge about the operational and safety aspects of channelized right-turn lanes explaining, to a large extent, the lack of guidance in practice. Survey results suggest a heavy reliance on engineering judgment by highway agencies in the use of channelized right-turn lanes and the selection of traffic control. Further, results confirmed a general perception in practice about the safety benefits of signal control at channelized right-turn lanes, despite the fact that such benefits were not supported by studies or statistics. The study emphasized the need for further research on the operational and safety aspects of this right-turn treatment at intersections. [ABSTRACT FROM AUTHOR]

Stop signs are the primary form of traffic control in the United States. However, they have a tendency to be much less effective than other forms of traffic control like traffic lights. This is due to their smaller size, lack of lighting, and the fact that they may become visually obscured from the road. In this paper, we offer a solution to this problem in the form of a mobile application implemented in the Android platform: Stop Watcher. It is designed to alert a driver when they are approaching a stop sign using a voice notification system (VNS). A field test was performed in a snowy environment. The test results demonstrate that the application can detect all of the stop signs correctly, even when some of them were obstructed by the snow, which in turn greatly improves the user awareness of stop signs. [ABSTRACT FROM AUTHOR]

This paper proposes an en route speed reduction to complement current ground delay practices in air traffic flow management. Given a nominal cruise speed, there exists a bounded range of speeds that allows aircraft to fly slower with the same or lower fuel consumption than the nominal flight. Therefore, flight times are increased and delay can be partially performed in the air, at no extra fuel cost for the operator. This concept has been analyzed in an initial feasibility study, computing the maximum amount of delay that can be performed in the air in some representative flights. The impact on fuel consumption has been analyzed, and two scenarios are proposed: the flight fuel remains the same as in the nominal flight, and some extra fuel allowance is permitted in order to face uncertainties. Results show significant values of airborne delay that may be useful in many situations, with the exception of short hauls where airborne delay may be too short. If cruise altitude is changed, the amount of airborne delay increases, since changes in cruise speed modify the optimal flight altitudes. From the analyzed flights, a linear dependency is found relating the airborne delay with the amount of extra fuel allowance. [ABSTRACT FROM AUTHOR]

The majority of high reliability organizational (HRO) research analysing the performance of the US Federal Aviation Administration's (FAA) air traffic control (ATC), nuclear power plants, and US Navy's aircraft carriers has treated these organizations as individual or separate units studied apart from the larger organizational frameworks in which they function. This research reports the evolution of the FAA's ATC reliability as a part of a larger high reliability system (HRS). A HRS construct was created as a result of a longitudinal case study spanning a period from 1905 to 2002 which analysed the development of the FAA's ATC service. The investigation focused on the emergence and institutionalization of policy- and agency-level HRO attributes in conjunction with emerging industry characteristics associated with high reliability. A three-tier model was identified that helps explain (1) how high reliability, low error operations evolved in the FAA, (2) how the HRS structure currently maintains reliability in the FAA's provision of ATC, and (3) how high reliability management is incorporated within a regulated US industry as a result of federal policy- and agency-level actions. Understanding how the aviation HRS manages the exceptionally safe and highly reliable ATC structure is important because this knowledge can be applied to other complex public safety and security policy and operational areas where high reliability is crucial. [ABSTRACT FROM AUTHOR]

The estimation of annual average daily traffic (AADT) is an important parameter collected and maintained by all US departments of transportation. There have been many past research studies that have focused on ways to improve the estimation of AADT. This paper builds upon previous research and compares eight methods, both traditional and cluster-based methodologies, for aggregating monthly adjustment factors for heavy-duty vehicles (US Department of Transportation Federal Highway Administration (FHWA) vehicle classes 4-13). In addition to the direct comparison between the methodologies, the results from the analysis of variance show at the 95% confidence level that the four cluster-based methods produce statistically lower variance and coefficient of variation over the more traditional approaches. In addition to these findings - which are consistent with previous total volume studies - further analysis is performed to compare total heavy-duty monthly adjustment factors, both directions of traffic, with direction-based monthly adjustment factors. The final results show that the variance as well as the coefficient of variation improve on average by 25% when directional aggregate monthly adjustment factors are used instead of total direction. [ABSTRACT FROM AUTHOR]

Recently, the IntelliDrive initiative has been proposed by the US Department of Transportation (USDOT) to enhance on-road safety and efficiency. In this study, we provide a mathematical framework which predicts the effect of such technologies on the efficiency of multilane highway systems prior to their real-life deployment. Our study shall encompass mixed traffic conditions in which a variety of assisted, automated and unequipped vehicles coexist. We show that intervehicular communications improves the flow of vehicles by reducing the perception-reaction (P-R) times of drivers and, in some cases, allowing for more efficient lane-changing operations. As we shall see, unlike the latter, the former effect of IntelliDrive on driver P-R time is always there, regardless of the specific traffic conditions. [ABSTRACT FROM AUTHOR]

The article presents an analysis of local regulations of secondary culprits using automated traffic enforcement schemes in the U.S. It discusses various aspects of traffic regulation including bad turn, speeding, and red light violations. It mentions federal court decisions that sustain these automated schemes challenged on constitutional grounds and preemption. It explores the possible governmental regulations in and out of traffic settings in the presence or absence of automated enforcement.

Abstract: Paratransit is a flexible demand-responsive form of public transportation intended for transporting mobility impaired individuals. This is the first study that estimates both demand and cost functions for publicly provided paratransit in the United States and the first to conduct a benefit-cost analysis for this mode. We find that the benefits of paratransit far exceed its associated costs. The results suggest that paratransit riders have few transportation alternatives available to them. We also find that the level of service matters in the demand for paratransit. [ABSTRACT FROM AUTHOR]

Abstract: How much can we tell about flows through networks just from their topological properties? Whereas flow distributions of river basins, trees or cardiovascular systems come naturally to mind, more complex topologies are not so immediate, especially if the network is large and heterogeneously directed. Our study is motivated by the question of how the distribution of path-dependent trails in directed networks is correlated to the distribution of network flows. As an example we have studied the path-dependencies in closed trails in four metropolitan areas in England and the USA and computed their global and spatial correlations with measured traffic flows. We have found that the heterogeneous distribution of traffic intensity is mirrored by the distribution of agglomerate path-dependency and that high traffic roads are packed along corridors at short-to-medium trail lengths from the ensemble of nodes. [ABSTRACT FROM AUTHOR]

Abstract: Contracted service comprises a significant proportion of total operating expenses in the provision of fixed-route bus transit service in the US. Despite its importance, the literature on the economic effects of transit service contracting has been limited to only a few studies since the mid-1990s, and is inconclusive due to problems with the nature and methodology of the past studies. This paper examines how the cost efficiency of providing fixed-route bus transit service varies by the degree of contracting. I make several improvements to previous studies and conduct a regression analysis that: (1) addresses the endogeneity problem between the contracting decision and cost efficiency, (2) differentiates between agencies that contract out only a portion of service from those that contract out all service, (3) takes into account the moderating effects of several factors on the effect of contracting on cost efficiency, and (4) uses a relatively larger set of cross-sectional time-series data constructed from the National Transit Database from 1992 to 2000. The analysis results show that the combined effects of contracting lower operating costs by $4.09 and $2.89 per vehicle hour for partial and full-contracting agencies, respectively, in the average case. These average cost savings translate into 7.8% and 5.5%, using the average operating cost per vehicle hour of $53.06. However, this improvement is not universal, because the effects of contracting on cost efficiency vary by factors such as peak-to-base ratio, agency size, the wage gap between bus operators in the public and private sectors, and agency type. [Copyright &y& Elsevier]

Usually, benefits from deploying an adaptive traffic control system are measured by comparing data collected in the field before the system is installed with those collected after the system is fully operational. Such an approach is costly because it requires installation of a system before potential benefits can be observed. Nowadays to investigate effectiveness of many alternatives that were traditionally investigated in field, microsimulation is used. However, how much can one rely on results from microsimulation? There has not been a single study in which benefits of adaptive traffic control systems measured in the field are compared with those obtained through microsimulation. This study presents such a research effort. The authors compared performance measures from a field evaluation of Sydney Coordinated Adaptive Traffic System in Park City, Utah, to their counterparts from microsimulation. They collected a significant amount of data to assess system performance in the field and to help build a microsimulation model. A 14-intersection model of the Park City network was developed, calibrated, and validated on the basis of multiple data sources. The results show that a validated microsimulation model can accurately reflect field conditions although such an effort can be very challenging. [ABSTRACT FROM AUTHOR]

A safety and security issue of concern for traffic managers and homeland security is the monitoring of flows on “planar surfaces,” such as ports and border areas. This article addresses the problem of locating surveillance radars to cover a given target surface that may have barriers through which radar signals cannot penetrate. The area of coverage of a radar is assumed to be a disc, or a partial disc when there are barriers, with a known radius. The article shows that the corresponding location problems relate to two well studied problems: the set-covering model and the maximal covering problem. In the first problem, the minimum number of radars is to be located to completely cover the target area; in the second problem a given number M of radars are to be located to cover the target area as much as possible. Based on a discrete representation of the target area, a Lagrangian heuristic and a two-stage procedure with a conquer-and-divide scaling are developed to solve the above two models. The computational experiences reported demonstrate that the developed method solves well the radar location problems formulated here. [ABSTRACT FROM AUTHOR]

The article discusses embedded multimedia processors to be used for road-traffic parameter estimation. These multimedia processors will provide the basis for future intelligent transportation electronic installations as directed by the U.S. Department of Transportation. Multimedia processors also provide special support for video applications.

This paper investigates the quantitative characteristics of the vehicle arrival pattern on highways. Inspired from a remarkable finding on data network traffic that most data packet arrival patterns follow the self-similar process as opposed to the classical Poisson process, this paper aims to explore whether the vehicle arrival pattern on highways exhibit the self-similarity property and the corresponding time headway distribution it obeys. By using real highway traffic data provided by the Texas Department of Transportation, United States, this paper examines the existence of self-similarity characteristics on these vehicle arrival data. This is done by estimating the Hurst parameter, which is an index for self-similarity testing. Hypothesis testing for the Hurst parameter estimation shows that the highway vehicle arrival pattern under moderate to heavy traffic conditions exhibit the self-similarity behavior. Then, using the headway data recorded from the Federal Highway situated in Kuala Lumpur of Malaysia, this paper further demonstrates that the time headway of vehicles on the highways follows the heavy-tailed distribution rather than the classical exponential distribution. These two novel findings not only shed some light on the existence of a new distribution to describe the vehicle arrival pattern but also enrich the studies on traffic flow theory. [ABSTRACT FROM AUTHOR]