Highway Users Research Articles

Urban freeway users' diversion response to variable message sign displaying the travel time of both freeway and local street

Most variable message sign (VMS) installed on the urban freeway only provide information about traffic conditions of urban freeway, but they do not provide traffic information about local streets. This study explores urban freeway users' diversion response to the D-VMS (VMS that display explicitly the travel time of both urban freeway and local streets) in the context of China. An on-site stated preference questionnaire survey was conducted to collect behavioural data. A cross-sectional binary probit model and a panel binary probit model are estimated to identify factors that influence drivers' diversion behaviour in response to D-VMS. The study showed that drivers' en-route decision on diverting from freeway to local streets can be significantly influenced by D-VMS and the extent of D-VMS impacts depends on driver characteristics, local street characteristics and D-VMS messages. Main findings regarding D-VMS impacts are, (a) travel time saving and drivers' years of driving experience serve as positive factors in diverting, (b) number of traffic lights on the local street, frequency of urban freeway use, being a mid-age driver, and being an employer-provided car driver, serve as negative factors in diverting. On the modelling aspect, it was shown that the panel model does not provide substantially different model coefficients but more robust statistical inferences for model coefficients as compared to the cross-sectional model, and the cross-sectional model tends to seriously overestimate t-test values for explanatory variables changing across drivers (e.g. demographic characteristics) but slightly underestimate t-test values for explanatory variables changing across scenarios (e.g. travel time savings). The findings have implications for better design and operation of advanced traveller information systems and for future effort on survey design, data collection and model estimation.

Sidebar: Be Seen and Be Safe Highway Safety with Farm Equipment Program

Ted Keen, a farmer from Wilson County, lost his life when a tractor trailer truck traveling 70 miles per hour rear-ended his tractor in the spring of 2003. This incident was the catalyst for addressing the issue of highway safety with farm equipment. Research data also indicated that this was a need for farmers in Wilson and the surrounding counties. The University of North Carolina Highway Safety Research Center reported that there were approximately 1,500 farm vehicle crashes in North Carolina from 1995 through 1999 [1]. Six counties in the 7-county area comprising Wilson, Nash, Edgecombe, Pitt, Wayne, Greene, and Johnston were among the top 12 counties in North Carolina in farm vehicle crashes during this period. In this 7-county area, there has been a 20.4% increase in population during the last decade. This has led to more motorists on the highways who are less familiar with agricultural equipment. In addition to the increase in population, farm operations have increased in size by 18%, requiring farmers with agricultural machinery to travel greater distances on highways, with larger, less maneuverable equipment. Under these conditions, farmers must implement safety practices that protect themselves and their employees. To address this situation, in 2004, Cooperative Extension conducted the Be Seen and Be Safe Highway Safety with Farm Equipment program and collaborated with the North Carolina Highway Patrol to offer educational training for farmers and their employees on highway safety with farm equipment. Extension agents received a grant from the North Carolina Tobacco Trust Fund Commission to fund this project. The objectives of the Be Seen and Be Safe project were to (1) decrease the number of agricultural machinery highway crashes, through farmer education and public awareness, and (2) to increase farmer adoption of safety practices with agricultural machinery on highways. Farmers need to be proactive in highway safety by increasing visibility of farm machinery on the highway. Taking actions that make agricultural machinery more visible will help motorists to see slow moving vehicles earlier. Extension agents researched and developed a presentation that advocated highway safety and encouraged farmers to be proactive. Sergeant Tom Futrell of the North Carolina Highway Patrol presented information on laws pertaining to farm machinery on highways. Agents developed and distributed a brochure that served as a reference and safety reminder for participants after the meeting. Farmers who attended the safety meetings received a safety kit that included items to increase their visibility on the highways, thus being seen and being safe. These items included a strobe light, a “Slow Moving Vehicle” sign, and 3 FARM (Fewer Accidents with Reflective Material) Saf Kits. More than 1,000 farmers and farmworkers participated in these educational meetings. Because of the large number of Spanish-speaking employees who operate farm equipment on highways, farmers asked the extension agents to conduct a Spanish version of the training. Agents used volunteers to translate the presentation, script, and safety brochure into Spanish. This training has been conducted numerous times during multiple years, in an effort to reach Spanish-speaking employees. At the meetings in each county, participants took a preand posttest, to determine knowledge gained from the presentations. In the 7-county area, farmers increased their knowledge by an average of 71%. Three months after the meetings, extension agents mailed all program participants an evaluation survey. Results indicated that 94% of respondents had installed the new slow moving vehicle signs on their farm equipment, 82% had marked farm equipment with reflective tape, 67% had installed the safety strobe light, 49% had purchased additional slow moving vehicle signs, and 92% had shared highway safety information with their employees. In 2004, the North Carolina Highway Patrol reported 39 crashes involving farm equipment in the project service area. This represented a 21.7% decrease in crashes, compared with an average of 49.8 crashes per year involving farm equipment, as reported by the University of North Carolina Highway Safety Research Center, from 1995 to 1999 for the area. Farmers responded to this educational program by increasing their visibility and being safe by becoming proactive in highway safety. The counties that have implemented the program’s recommendations have benefited by reducing the number of crashes involving agricultural equipment, and the reduction in the number of crashes has saved lives and prevented serious injuries. Patience is a trait that should be exercised by all highway users, and doing so will allow everyone to go home safely at the end of the day. That patience helps the agricultural industry continue to be North Carolina’s number one provider of income, at just over $72 billion annually. Sharing the road is everyone’s responsibility, and being proactive about preventing a possible injury incident is just plain smart.

What is greener than a VMT tax? The case for an indexed energy user fee to finance us surface transportation

Charging highway users per mile has been proposed as a replacement for the US motor fuel tax. A miles traveled user fee, however, does not encourage energy efficiency in vehicle design, purchase and operation, as would a user fee levied on all forms of commercial energy used for transportation and indexed to the average efficiency of vehicles on the road. An indexed roadway user toll on energy would induce two to four times as much reduction in greenhouse gas emissions and petroleum use as a pure mileage fee. However, it is not a substitute for pricing greenhouse gas emissions and would make only a small but useful contribution to reducing petroleum dependence. An indexed energy user fee cannot adequately address the problems of traffic congestion and heavy vehicle cost responsibility but it could be a component of a system of financing surface transportation that would eventually also include time and place specific monitoring of miles traveled for congestion pricing, externality charges and heavy vehicle user fees.

Ride Specifications

Road roughness is a major factor in pavement condition because of its effects on pavement resurfacing and vehicle operating costs. Rougher pavements require more frequent resurfacing, generate complaints from highway users, reduce optimum travel speeds, disrupt traffic flow, and create safety hazards. Ride specification is one of the tools practiced by almost all state agencies including the Virginia Department of Transportation (DOT) to achieve the desired smoothness on the road. A ride specification dictates the level of smoothness from paving projects and can adjust the contractor's payment, depending on the finished ride. Virginia DOT's experience, accomplishments, and challenges with ride specifications are presented. Through application of the ride specification during the past decade, the ride quality on Virginia's rideability project roads has continued to improve. The average roughness after paving has improved dramatically in the past few years compared with that of the early 2000s. Between 2005 and 2009, 3,068 lane miles were paved according to the ride specification and a net bonus of $4,928,422 was paid to contractors. The benefit of having smoother roads could result in direct savings to an agency from deferring resurfacing activities by about 2 years and substantial savings in terms of fuel efficiency (especially for the trucks), reduced congestion due to deferred resurfacing, reduced vehicle maintenance costs (from smoother roads), and other benefits. The estimated benefits from applying the ride specification during 2005 to 2009 are found to far outweigh the cost.

Rethinking the Politics of Freeway Congestion Pricing

A growing community of transport economists and urban planners has concluded that the best solution to U.S. freeway congestion would be to implement congestion pricing on all such freeways. At the same time, many political scientists and other political observers consider doing so to be politically impossible, primarily because of strong opposition from taxpayers, voters, and highway user groups. Federal efforts (dating to the 1970s) to induce one or more urban areas to price its freeways have been unsuccessful; this lack of success reinforces the political scientists' skepticism. This paper suggests that even if the political difficulties could be overcome, the conventional model of freeway congestion pricing (charging all users the same variable price) may not be optimal: this model could well create more losers than winners. In analyzing this conundrum, the author looks more closely at two assumptions implicit in the standard congestion pricing model: uniformly applied (variable) pricing and all general purpose lanes. Revisiting both assumptions leads to a proposal for multitier pricing on differentiated lanes, which the author suggests could be more politically feasible and productive of larger economic benefits. This approach also lends itself to being implemented in an evolutionary manner, in which each step is justified on its own merits, without regard of the possible longer-term end.

Reduced-Conflict Intersection

The selection of the appropriate geometry and traffic control for intersections on high-speed arterial highways often requires balancing increased highway user costs with attempts to control construction costs. Providing a safe design that is cost-effective is always a primary consideration in deciding on a solution. Another issue is that one form of intersection and traffic control may be optimal during peak traffic times on an average day but may not have sufficient capacity for extreme peak times such as those for events or on recreational routes. Alternatively, those same controls can cause needless delay when traffic is lighter. Examples include traffic signals that operate 24 h/day and roundabouts that require all traffic to slow dramatically, regardless of the amount of conflicting traffic. This study presents a group of new alternative intersection designs designated as reduced-conflict intersections. This study describes those designs and their associated traffic control, which consists of a demand-based traffic signal system. This study then presents the results of a comparative analysis of this new type of intersection along with other designs, including a conventional intersection with signal control, two forms of roundabouts, and the super street intersection. The results of the study show that the reduced-conflict intersection may be an effective addition to the toolbox of intersection designs.

A Simulation-Based Approximation Algorithm for Dynamic Marginal Cost Pricing

This work offers a simulation-based approximation algorithm for dynamic marginal cost pricing (MCP) congestion pricing that is a direct extension of its static counterpart. The algorithm approximates the time-dependent marginal costs, and is incorporated into the inner approximation dynamic user equilibrium algorithm to evaluate the results of dynamic MCP, which are then compared to static assignment results with MCP from previous study. The status quo and dynamic MCP-on-freeways scenarios are simulated (and then compared) on the Dallas-Fort Worth 35,732-link network. Due to computational requirements for such a large-scale dynamic traffic assignment application, the dynamic MCP scenario is simulated without feedback, and only route choices are permitted to vary. When prices are imposed on freeway users, some minor system benefits are observed, including a delay in the onset of congestion. Dynamic prices vary substantially over the three-hour period of analysis, reflecting changes in freeway congestion. Reasons for any inconsistencies between dynamic and static results are discussed, along with important enhancements to future implementation.

Determination of Contract Time and Incentive and Disincentive Values of Highway Construction Projects

Although ultimately bringing long term economic benefit, highway construction activities temporarily increase highway user costs and non-user costs, and affect highway safety and the environment. In order to minimize the negative effects of construction projects, state highway agencies have been using incentive/disincentive clauses in contracts to reward contractors for early completion of projects, and to recover the engineering and administrative costs incurred when contractors miss completion deadlines. Evaluation of excess user costs of traffic delays caused by the presence of work zones is essential for assessment of the impact of the work zones on the public. The estimated user costs provide highway engineers and construction managers with useful information for effective highway construction planning. For any highway construction project, there exists a construction time that would minimize the construction cost with given manpower and equipment. If the project is shortened or prolonged from this construction time, the construction cost will increase. This article shows that reasonable incentive and disincentive values can be determined by including a portion of the work zone user costs in the relationship between construction time and construction costs.

Assessing Casualty Risk of Railroad-Grade Crossing Crashes Using Zero-Inflated Poisson Models

A railroad grade crossing (RGC) is a spatial location where rail and highway users share the right-of-way. A significant number of traffic crashes and severe consequences at RGCs have signaled the need for appropriate models to investigate the key factors associated with the casualty risk level at an RGC in terms of the number of fatalities or injuries caused by one or more crashes in a specific time period. This study used a zero-inflated Poisson regression model to describe the relationship between the extra-zero count fatality or injury data and explanatory variables collected at 592 RGCs in Taiwan. The annual averaged daily traffic and the presence of Guidance Sign 31 were significantly associated with the probability of no fatality or injury encountered at an RGC; if an RGC was at risk of a fatality or injury, the number of daily trains, crossing angle, and Guidance Sign 31 significantly influenced the expected total number of fatalities or injuries caused by traffic crashes. The empirical results indicated that traffic exposure and traffic signage have significant effects on the risk levels of casualties at an RGC.

Sleep disorders and accidental risk in a large group of regular registered highway drivers

Objective Despite convincing evidence regarding the risk of highway accidents due to sleepiness at the wheel, highway drivers still drive while sleepy. Sleep disorders can affect driving skills, but the relative impact of sleep complaints among a large population of highway drivers is still unknown. Methods Out of 37,648 questionnaires completed by frequent highway users (registered in an electronic payment system), we ran our analyses on 35,004 drivers who responded to all items. The questionnaire previously used in a telephone survey included socio-demographics, driving and sleep disorders items (Basic Nordic Sleep Questionnaire) and the Epworth Sleepiness Scale. Results Of all drivers, 16.9% complained of at least one sleep disorder, 5.2% reported obstructive sleep apnea syndrome, 9.3% insomnia, and 0.1% narcolepsy and hypersomnia; 8.9% of drivers reported experiencing at least once each month an episode of sleepiness at the wheel so severe they had to stop driving. One-third of the drivers (31.1%) reported near-miss accidents (50% being sleep-related), 2520 drivers (7.2%) reported a driving accident in the past year, and 146 (5.8%) of these driving accidents were sleep-related. The highest risk of accidents concerned patients suffering from narcolepsy and hypersomnia (odds ratio 3.16, p < .01) or multiple sleep disorders (odds ratio 1.46, p < .001). Other major risk factors were age [18–30 years (OR 1.42, p < .001)] and being unmarried (OR 1.21-fold, p < .01). Conclusions In regular highway drivers, sleepiness at the wheel or sleep disorders such as hypersomnia and narcolepsy are responsible for traffic accidents independent of age, sex, marital status or socio-professional categories.

A New Approach for Allocating Highway Costs

The allocation of highway costs is constantly debated among legislatures, highway agencies, and highway users as it directly relates to concerns about equity in terms of cost responsibility and actual user charges. One of the major challenges in highway cost allocation stems from the need to estimate pavement damage by different vehicle classes. Normally, the calculation of damage caused by heavy vehicles to the highway infrastructure utilizes the concept of Equivalent Single Axle Load (ESAL). This concept was empirically established after the American Association of State Highway Officials America (AASHO) Road Test almost half a century ago. Although the ESAL concept is widely used in pavement design, it has a number of shortcomings when applied for the estimation of pavement damage by different vehicle classes. Some of these limitations include: failure to account for specific infrastructure and environmental conditions, disregard of the differences in traffic configurations and composition, and the inability to capture different distress types. This leads to a fairly inaccurate and generic estimation of pavement damage by vehicle class. This paper proposes an innovative and more rational highway cost allocation approach based on the recently completed guide for the "Mechanistic-Empirical Design Guide of New and Rehabilitated Pavement Structures" developed under the National Cooperative Highway Research Program (NCHRP) Project 1-37A. The Guide accounts for all factors that contribute to pavement deterioration, thereby addressing the shortcomings of an ESAL-based analysis listed earlier. Estimates for pavement damage attributable to each vehicle class can thus be accurately simulated. For the purposes of this study, traffic data collected at a weigh-in-motion station in Texas were used to estimate the highway cost shares of different vehicle classes, given different pavement structural capacities.

Benefits, Costs, and Financing of Truck-Only Highway Lanes

As increasing amounts of intercity freight are transported by trucking firms, the possibility of constructing truck-only lanes along selected rural Interstate highways warrants consideration. On heavily traveled sections, there is potential for improvements in safety and productivity if such lanes were added. In this paper, we explore the conditions under which investment in truck-only lanes could be considered and what sorts of benefits may accrue to both occupants of passenger vehicles and to operators of heavy trucks. Then we examine the available evidence regarding the nature and magnitude of these benefits to gain insight into the willingness of highway users to pay for these lanes. We conclude that the willingness to pay for truck-only lanes on the part of occupants of passenger vehicles appear to be quite limited and that support for these lanes on the part of trucking firms is likely to depend upon their being allowed to operate longer-combination vehicles (LCVs) on them. Trucking firms could be assessed tolls to travel in truck-only lanes, with these tolls representing some fraction of the increased productivity gained through being allowed to operate LCVs. Finally, we pose several questions that would need to be answered before an investment in truck-only lanes might be considered along a given Interstate segment.

Self-Financing and Distance-Based Highway Pricing Scheme: State Highway System Perspective

A distance-based highway pricing scheme has been considered a means to tackle highway revenue shortfalls as an alternative to the current taxation on motor fuels. To establish fee rates for a distance-based pricing scheme, this study argues that maintenance and management of the highway system be self-financed by its users, who are responsible for maintenance, repair, and rehabilitation of the highway system. Each user’s highway cost responsibility is determined by its vehicle class, road functional class, types and frequency of interventions, and other technical parameters. This paper uses the State Highway Cost Allocation Study (HCAS) tool to analyze expenditures, revenues, and usages of a state highway system to obtain cost borne by various user groups. On the basis of Indiana State Highway data, cost responsibility of each highway user varies between 0.66¢/km and 25.05¢/km among 20-vehicle types. Sensitivity analysis was carried out considering several technical parameters including load equivalency factor, non-load-related impacts on pavement, and minimum requirements for construction and rehabilitation to reveal the reasonable ranges of cost responsibility of different users.

Highway work zone safety audits for safety improvements

PurposeThe paper aims to review current practices of road safety audits worldwide, investigate the perceptions of experts on highway work zone safety in the USA and issues of adopting work zone safety audits in the country, and propose a framework for developing guidelines for implementing work zone safety audits for safety improvements.Design/methodology/approachThe paper was conducted by reviewing the existing literature of road safety audits and administering four‐week questionnaire surveys of experts on highway work zone safety in the USA.FindingsRoad safety audits have been successfully adopted worldwide to maximize safety of the roadway environment for highway users. The questionnaire surveys have clarified leading causes of work zone safety problems and effective countermeasures, types of projects suitable for auditing and audit frequencies, audit team composition and funding sources, audit tasks and tools, and project staff safety training audits. A similar procedure for road safety audits could be adopted for work zone safety audits with emphasis on mitigating work zone safety impacts.Research limitations/implicationsAdditional survey participants from the highway user group may add valuable insights into the use of highway work zone safety audits for safety improvements.Practical implicationsThe paper findings would assist in preparing strategies and methodologies for developing the national highway work zone safety audit guidelines in the USA.Originality/valueThe work zone safety audit guidelines to be developed could help transportation practitioners effectively conduct work zone safety audits for safety improvements in the country.

Distributional impacts of changing from a gasoline tax to a vehicle-mile tax for light vehicles: A case study of Oregon

A vehicle-miles traveled (VMT) tax is frequently mentioned as viable alternative to a fuel tax for collecting highway users fees from light vehicles. Both a static model and a regression based model are used here to assess the distributional impacts of a switch from a fuel tax to a VMT tax for the state of Oregon. The VMT tax is found to be slightly more regressive than the fuel tax and rural households are found to actually benefit relative to urban households under a VMT tax. Two alternative VMT structures that might increase incentives to use more fuel efficient vehicles are provided, but both are found to be even more regressive than a flat VMT tax .

The Citizens' Guide to Transportation Reauthorization

Sometime in 2010 or 2011, Congress expects to decide how to spend the $250 billion or more of federal gas taxes and other highway user fees that will be collected over the next six years. The process of doing so is called surface transportation reauthorization. A major point of contention in this law is how much of our transportation system should be centrally planned and how much should be built and operated in response to the needs of actual transportation users. Advocates of top-down planning want to reduce per capita driving by providing disincentives to automobiles, such as increased congestion and driving costs, and funding expensive alternatives such as high-speed rail and rail transit. Even if you believe in the goal of reducing per capita driving, the evidence indicates that these tools have minimal effect on driving and may even be environmentally counterproductive. Advocates of customer-driven transportation want to fund transportation out of user fees, not taxes, and make transportation providers — whether public agencies or private parties — responsive to the needs and desires of those users. Decades of experience have proven that the best way of reducing the environmental costs of transportation is to use new technologies to reduce the impacts per mile of mobility, not to reduce mobility itself. This citizens’ guide presents the basic facts behind these two views.

Guidance on Design and Application of Rumble Strips

Many transportation agencies use shoulder rumble strips to address the problem of single-vehicle run-off-the-road crashes by alerting inattentive or drowsy motorists that their vehicles have drifted out of the travel lane. The application of rumble strips has expanded to include the installation of centerline rumble strips along the centerlines of undivided highways to reduce head-on and opposite-direction sideswipe crashes. Installing rumble strips along either the shoulder or centerline without considering the effect on other highway users (i.e., bicyclists and motorcyclists) may lead to unintended consequences. This research addresses a number of safety issues: (a) the safety effectiveness of shoulder rumble strips on different roadway types, (b) the safety effectiveness of shoulder rumble strip placement relative to the edgeline, (c) the safety effectiveness of centerline rumble strips on different roadway types, and (d) the safety effectiveness of centerline rumble strips along horizontal curves and tangents. The safety evaluations considered all severity levels (total crashes) and fatal and injury crashes. Statistical models for predicting noise levels in the passenger compartment of a vehicle for use in designing rumble strip patterns were also developed. The results of this research were combined with results from previous research to address important policy issues for transportation agencies to consider in the design and application of shoulder and centerline rumble strips.

Environmental Analysis in Transportation

Since 1999, the I-90 Snoqualmie Pass East Project (I-90 project) of the Washington State Department of Transportation (WSDOT) team has worked with dozens of government agencies and nongovernmental groups to develop a range of potential solutions to meet project needs and mitigate the project's potential adverse impacts on the Central Cascades’ ecosystem and the state's economy. WSDOT created a multiagency interdisciplinary team (IDT) as an advisory body to recommend a preferred alternative that incorporated relevant science and the concerns of agency stakeholders. The project's original IDT included eight primary and advisory agencies and was later expanded to include 12 participating agencies. The IDT went on to form the mitigation development team (MDT), a technical advisory subcommittee consisting of hydrologists and biologists from different agencies, to identify locations and develop performance criteria for investments in ecological connectivity. In addition to the IDT and the MDT, formal technical committees were formed to assist in planning and permitting challenges for final designs on wetlands mitigation, wildlife monitoring, and stormwater. WSDOT has also established innovative partnerships with university researchers and conservation groups to help establish citizen awareness, wildlife monitoring, and targeted habitat acquisitions. Relationships with transportation-based organizations and businesses were formed to gain insight into the requirements of highway users. WSDOT's innovative approach to developing partnerships to understand and meet landscape-scale, watershed-based objectives on the I-90 project provides a scalable model for the integration of context-sensitive solutions for future WSDOT and other state departments of transportation projects.

Bilevel Highway Route Optimization

A new bilevel highway route optimization model finds highway alternatives that best improve the existing roadway system while optimizing the alternatives' alignments on the basis of geometric, cost, and operational considerations. The upper level of the bilevel structure represents a decision-making process of system designers in which possible highway alternatives are generated and evaluated. The lower level represents highway users' route choice behavior and evaluates how traffic in an existing road network is redistributed by the new highways. Various highway agency and user-related costs (such as earthwork, right-of-way, and travel time costs) are included in the model's objective function and used as key evaluation criteria. The model is tested with an example to check its capabilities and use in real-world applications. The results show that the model can optimize solutions within a reasonable computation time and that locations of the new highways are sensitive to redistributed traffic in the modified road network as well as to unit costs and other inputs. It is expected that highway planners and designers can greatly benefit from the proposed model, which offers optimized candidate alternatives identified by comprehensive bilevel optimization procedures rather than merely satisfactory alternatives obtained from the trial-and-error process of the traditional approach.

Disaggregate Propensity Study on Red Light Running Crashes Using Quasi-Induced Exposure Method

Red light running (RLR) is a serious traffic hazard at signalized intersections. A number of studies have been undertaken to understand the characteristics and prevalence of highway users involved in RLR crashes. However, most of the studies did not consider crash exposure systematically. To overcome the difficulties in obtaining direct exposure information, this study made use of the quasi-induced exposure method to identify the significant driver-vehicle characteristics that influence RLR crash propensity. This was done by developing models of relative exposure for intersections and relative crash involvement ratio for RLR crashes. Using crash data in Singapore from 1993 to 2002, a disaggregate analysis identified a number of significant factors contributing to RLR crash propensity for different driver age and gender groups, and vehicle types under various road environments. The results show that the problem related to RLR crashes is not just related to driver or vehicle or the road environment but a combination of these factors. Arising from the results of this study, potential countermeasures in reducing the high RLR crash risk for specific highway user cohorts are discussed and recommended.