Transportation Research Record: Journal of the Transportation Research Board

A preliminary assessment is made of the impact of increasing the gross vehicle weight (GVW) from current legal limits to 100,000 lb (45 400 kg) on vehicles hauling sugarcane, rice, timber, and cotton. Sections of road were chosen in each area of Louisiana where commodities are produced, the amount of each commodity hauled was estimated, and the effects of increasing the GVW were evaluated for each section using pavement design models. Design data were secured from the Louisiana Department of Transportation and Development computer database and project files to determine the pavement design parameters and traffic estimates for each road. The number of vehicles hauling the 1998 harvest payload was estimated, a projected increase in the production of each commodity was estimated on the basis of government statistics, and rehabilitations were designed with the use of the 1986 AASHTO Design Guide for a 20-year analysis period. Present worth (PW) was calculated for each GVW scenario for each roadway. Comparisons of PW between the weight scenarios showed that increases in GVW have more effect on state and U.S. highways than they do on Interstate highways. Any increase in GVW over current limits increases the cost of overlays and decreases the length of time before an overlay is required. The cost increase due to increasing the GVW is substantial. Fee structures should be modified by the legislature so that these costs are paid for either through the current registration and overweight permit fee structure or through some new tax, such as a ton-mile tax.

A method to identify the attractiveness for private financing of a transport infrastructure project is presented. The objective of the method is to assist the public sector in identifying the attractiveness of a transportation infrastructure project for private financing, highlighting the factors that tend to reduce such attractiveness and providing the means to examine the viability of alternative risk-allocation scenarios related to risks undertaken by the state or private sector. The method allows for the simulation of the private sector’s attitude toward risk, employing practices of risk assessment in investments. Its innovation lies in how the whole process is structured so that participants understand beforehand whether an agreement can be concluded and which factors involved are critical. A key property of the method is the ease by which priorities of different risk components are synthesized into a hierarchical form through pairwise comparisons. This method, although targeted primarily for the public sector, could assist both private and public stakeholders investing in transport infrastructure projects (termed private-public partnerships) to reach an agreement. Basically, it is an interactive process characterized by the conflicting objectives and judgments of both public and private sectors.

The idea of road pricing as a function of congestion costs in the United Kingdom (U.K.) was put forward in a seminal report published by the U.K. Ministry of Transport in 1964. After 35 years, little has been done and the reasons behind this delay are mainly political, as the failure to implement congestion metering in Cambridge at the beginning of the 1990s shows. The subject has taken on a new urgency now that the U.K. government has announced its intention to authorize local councils to introduce road charges. Road pricing has a strong theoretical basis, but congestion costs must be quantified before it can be implemented. For that purpose, a simulation model is used. The social costs of congestion are measured by the deadweight loss and calculated from the difference between the marginal social costs and the price actually paid by trip makers. An exercise was done for two similar towns, Cambridge and York, and potential road charges differing by only 8 percent on average were obtained. This seems to strengthen the idea that finding road charges in a few cases, each one characteristic of a larger set of towns, would allow the provision of guidelines to local councils. In that way, fair road prices could be established across the U.K. The use of revenues from public-accepted road charges is also discussed.

Usage of the QuickRide program on the Katy high-occupancy vehicle (HOV) lane in Houston, Texas, is described. The QuickRide program allows two-person carpools to use the HOV lane for $2.00 during peak periods when the lane is restricted to three or more persons. Use of QuickRide during its first year is described, and an analysis of the demand for the program is presented. QuickRide usage, reported travel behavior, and demographic data are used to analyze user travel patterns, travel time savings, and frequency of use. In the 1-year demonstration, demand averaged slightly over 100 vehicles per day, with more than 60 percent of these vehicles traveling in the morning peak. Participants' average use of QuickRide was only about 0.9 times per week, and very few participants used it more than five times per week. Yet a sampling of travel days indicates that, for the $2.00 fee, the average vehicle saves about 20 min of travel time. Responses to a mail-back survey show a significant mode shift from drive-alone to QuickRide, amounting to more than 50 percent of QuickRide trips. A substantial shift was also seen in the time of travel into the peak hour, totaling about one-third of QuickRide trips. Finally, larger household sizes and higher incomes appear to be good predictors of QuickRide use. Interestingly, previous use of the HOV lane was not a good indicator, either positively or negatively, for the frequency of use of QuickRide. These results suggest that (a) the total demand for HOV-2 value pricing may be limited in major travel corridors, despite large potential time savings; (b) substantial shifts in mode and time of travel are possible with HOV-2 value pricing; and (c) household size and income are good indicators, but HOV lane use is a poor indicator, of the frequency of use of an HOV-2 value pricing program.

Variable time-of-day toll pricing was introduced in Lee County, Florida, in August 1998, on two of the area’s five bridges. Discounted tolls were offered to drivers with transponders (required for electronic toll collection) traveling in time periods just before and after typical peak demand travel periods. A telephone survey of 400 Lee County residents was conducted in late 1998. This survey was designed to collect information on driver travel behavior and determine participation levels in the variable pricing program. The survey found that the true participation level in the variable pricing program is in the range of 2.25 percent to 9.25 percent of survey respondents. The survey also examined potential adverse effects of changes in toll prices (induced demand, changes in mode of travel); perceptions of inequity by those unable to benefit from time-of-day toll pricing; and the socioeconomic characteristics of variable pricing participants. Eligibility for the discounted tolls was restricted to only those drivers who pay their tolls electronically. Participants and nonparticipants in the variable pricing program appear to differ by type of employment and household type. Those stating they do participate in variable pricing were less likely to be employed full time than those who do not participate. Differences were also found in the primary trip purposes of participants and nonparticipants. Commuters and drivers on work-related travel were less likely to participate in the program. It can be inferred that those with flexibility in their travel plans can, and do, change their travel to take advantage of the variably priced tolls.

Transport strategies in Dublin before 1990 were primarily road based with particular emphasis on increasing road space within the city for the car. In the early 1990s, however, the Dublin Transportation Initiative recommended a more innovative strategy, the core of which centered on public transport. Implementation of the strategy is currently under way, but increased economic activity, with associated increases in car ownership and usage, has undermined the potential to address the imbalance between transport demand and supply, particularly in the shorter term. As a result, feasible and reliable public transport alternatives do not currently exist for car users on some radial corridors. The ongoing implementation of bus lanes and an increase in the number of buses should go some way in improving the reliability of the service. It is against this background that road use pricing is considered. The potential user response to road user charging is examined by means of a pilot action project to investigate whether further evaluation of the measure would be justified on a larger sample. The distance-and-time-based time-differentiated pricing method used in the pilot action induced a significant decrease of 22 percent in car trips and a 23 percent reduction in distance traveled during the peak period, reflecting the relatively high road use charges applied in that period. The total distance traveled decreased by 13 percent. The road user charge reflects the marginal external costs of car travel in the peak period in Dublin.

In August 1998 the Midpoint and Cape Coral Bridges in Lee County, Florida, began charging variable tolls based on the time of day. Traffic data collected at these two bridges are examined, including the number of vehicles, by transaction payment type and by time of day. These data were analyzed to determine if variable pricing toll discounts have changed traffic patterns at the toll bridges. Data collected from January through July 1998 (before the implementation of variable pricing) were compared to data collected from August through December 1998 (during variable pricing). The data were examined in both aggregate and half-hour time increments throughout the day. This allowed for initial analysis of ways that traffic volumes have shifted by time of day due to discounted tolls. Data were also collected on the payment methods of all bridge users. This information is critical, since only those users paying their toll electronically (approximately 23 percent of transactions) are eligible for the variable pricing toll discounts. Therefore, two groups were examined separately—eligible users (the test group) and ineligible users (the control group). Variable pricing was found to have caused significant changes in the travel behavior of eligible users. On the Cape Coral and Midpoint Bridges, the number of eligible users increased significantly during the discount periods and decreased significantly during the peak periods. In contrast, changes in the traffic patterns of ineligible users were found to be statistically insignificant.

Oregon’s weight-mile tax was amended in 1990 to provide for a lower tax rate for trucks weighing more than 36 320 kg (80,000 lb) to which axles were added. The additional axles within a weight class reduce the amount of road damage. The tax break was largely based on equity considerations, since trucks within a weight class tend to do less road damage if they have more axles. However, the tax reductions also created an economic incentive to add axles and thus reduce road damage. Whether the tax break actually led to an increase in the number of axles within weight classes and a reduction in the amount of road damage is investigated. Statistical data indicate that a small increase occurred in the number of axles in most weight classes and a large increase occurred in mileage by the heaviest trucks with the most axles. These increases reduced the damage per ton shipped on trucks subject to the axle incentive, but to determine if this was due to the weight-mile tax is not possible. A series of structured interviews supplemented the statistical analysis and indicates that the tax incentive is not a major determinant of truck configuration. One reason for this is that regulatory constraints, particularly weight limits, limit the effectiveness of the tax incentives.

Road user costs (RUC) are defined as the estimated incremental daily costs to the traveling public resulting from the construction work being performed. Those costs are primarily time lost because of conditions such as detours/rerouting that add to travel time, reduced roadway capacity that slows travel speed and increases travel time, or a delay in the opening of a new or improved facility that prevents users from gaining travel time benefits. In Texas, RUC analyses and associated liquidated damages have been applied predominantly to high-profile urban freeway reconstruction projects, which are ideal candidates for RUC application because of the potential for very high motorist delay costs. A much wider range of projects involving the addition of capacity can be considered for RUC. Not all potential projects, however, are as complicated as urban freeway reconstruction efforts that require detailed simulation modeling to determine the value of RUC. The results of a research study that developed a manual technique for determining RUC are documented, along with associated liquidated damages for typical added-capacity and highway rehabilitation projects. The technique involves a series of look-up tables that provide RUC values on the basis of project type and a minimal number of project attributes. Two different approaches were employed: a before-and-after approach for added capacity projects and a during-versus-after-construction approach for rehabilitation projects.

Travel-related and damage-avoidance benefits and costs of conducting seismic retrofit improvements to arterial bridges are examined, with consideration of the risk posed by a relatively low probability but high damage earthquake (a design level event). The city of Seattle’s arterial bridges and viaduct structures serve as vital components of the urban road network, providing for the ongoing transportation needs of citizens and commerce. Failure of these bridges in the event of an earthquake would have significant negative impacts for the movement of people and goods, and thus on the local economy. Shoring up the city’s bridges to resist earthquake damage would clearly bring benefits, thereby preventing the impassable arterial bottlenecks that would otherwise occur. The question is whether or not the potential benefits of seismic retrofit improvements warrant their investment costs, thereby providing an economically efficient use of public dollars. For the purpose of addressing this question, a methodology for evaluating the potential benefits and costs associated with bridge seismic retrofit improvements is presented, quantifying these impacts for a two-phase retrofit program and considering the results in light of risk and uncertainty. The evaluation procedures developed consider a major earthquake with defined probability and compare the travel-related and damage-avoidance benefits that would be generated by retrofit improvements with their associated implementation costs. Emphasis is placed on travel impacts because researchers would find nontransportation economic impacts extremely difficult to quantify without knowing all of the other physical, built environment impacts that would occur with a major seismic event. Standard measures of economic feasibility are reported, and in the case of Seattle, seismic retrofit improvements demonstrate moderate positive economic rates of return. The implications posed by expected utility theory for risk-averse decision makers in such cases involving earthquake uncertainty are also discussed.

The major corridor investment-benefit analysis system recently developed for the Indiana Department of Transportation (INDOT) is discussed. The purpose of the system is to provide an analytical tool for use by INDOT in evaluating and comparing the impacts of major corridor highway investments in the state. The system combines a statewide travel demand model, a user benefit-cost analysis model, and a regional econometric model. The conceptual approach behind the model is described, and the results from an application of the model to analyze the transportation and economic impacts of the upgrade of US-31 between Indianapolis and South Bend, Indiana, to Interstate level of service is presented. Issues addressed by the model include the impact of travel time savings and other user benefits on business users of the highway, as well as the potential for the study corridor to attract new businesses or tourists as a result of improved access to markets.

Continuous growth of road transportation demand has resulted in soaring rates of road deterioration and maintenance costs. Full road cost recovery by direct charging of road users is gaining more popularity as governments face pressure to reduce general taxes, and full road cost recovery can promote more efficient use of the road system. A sound charging system requires reliable models for infrastructure deterioration and sound methodologies for cost allocation. In Ontario, new pavement performance models have been recently developed with more emphasis on separating the effects of traffic from the effects of environmental forces on flexible pavements in different geographic locations. The recent models and data have been used to investigate the cost implications of different vehicle configurations and road characteristics for the Ontario pavements and bridges. The results are used for the allocation of costs to various users of the road system. The results generally have implied that initial road design specifications, vehicle configurations, and the types and locations of roads could significantly affect user cost responsibilities. The analyses determined that proper selection of vehicles and payload amounts could result in up to 6 percent savings in pavement costs. The analyses showed that a fair and efficient cost allocation can be achieved by consideration of various vehicle and road characteristics and their interrelated cost implications, rather than solely on the basis of damage implications of each vehicle.