Researchers identified a potential methodology for obtaining the incremental societal costs and benefits from a variable pricing project and applied that methodology to the QuickRide high occupancy/toll (HOT) lanes in Texas. This is one of the longest running variable pricing projects in the United States and, as such, it provided useful historical data and trends upon which to estimate future benefits and costs. This analysis found that the incremental societal benefits of QuickRide exceeded incremental societal costs for the time period considered. A companion paper that used the same methodology to examine the benefits and costs of the SR-91 Express Lanes found similar results. However, the differences between the benefits and costs were dramatically different for the two projects, indicative of the relative size of the two projects and the number of travelers impacted. On SR-91, tens of thousands of travelers were impacted on a daily basis where QuickRide’s impact was limited to approximately 400 travelers per day. Interestingly, the benefit-cost ratios of the two projects were similar, both between 1.5 and 1.7.

Researchers identified a methodology for obtaining the incremental societal costs and benefits for a variable pricing project and applied that methodology to the State Route 91 (SR-91) Express Lanes in California. This is the longest running variable pricing project in the United States and, as such, it provided useful historical data and trends upon which to estimate benefits and costs. This analysis found that the incremental societal benefits of the SR-91 Express Lanes exceeded costs for the time period considered. A companion paper that examines the benefits and costs of the QuickRide high occupancy/toll lane program found similar results. However, the magnitudes of the differences in benefits and costs were dramatically different for the two projects, indicative of their relative sizes and the numbers of travelers impacted. On SR-91, tens of thousands of travelers were impacted on a daily basis where QuickRide’s impact was limited to approximately 400 travelers per day. Interestingly, the benefit-cost ratios of the two projects were similar, both between 1.5 and 1.7.

Right-turn lanes are used to provide space for the deceleration and storage of turning vehicles and to separate the turning vehicles from the through movement. When larger corner radii are used at the right turn, vehicles can turn at higher speeds (thereby minimizing speed differential between turning and through vehicles). A concern with the higher operating speed is the challenge it provides pedestrians. This project analyzed the impact of right-turn treatments on right-turn vehicles speeds at 19 urban approaches. Each approach had an exclusive right-turn lane that was separated from the through lane with either a lane line or a raised corner island. The 85th percentile free-flow speed near the middle of the right turn ranged from 20.9 to $33.8\mathrm{km}∕\mathrm{h}(13\text{–}21\mathrm{mi.}∕\mathrm{h})$ while on the approach it ranged from 27.4 to $46.7\mathrm{km}∕\mathrm{h}(17\text{–}29\mathrm{mi.}∕\mathrm{h})$ . Speed prediction equations were developed as part of this study.

The paper presents a capacity estimation model for a signalized intersection approach with a short right-turn lane. The proposed model overcomes one of the major shortcomings of the current capacity estimation methodologies by considering the probabilistic nature of traffic flow and the effect of queue blockage to the short-lane section. The research showed that the capacity of a signalized intersection with a short right-turn lane is strongly related to the length of the short lane, the proportion of through and right-turn vehicles, and cycle length. The study also revealed new findings, through simulation, on the saturation flow rate discharging from the single-lane section where the right-turn lane splits. It was found that the saturation flow rate increases with the increase of the length of the right-turn lane. The proposed model was validated against the results from CORSIM, a microscopic traffic simulation model, and found general agreement between the two results. Capacity enhancement is achieved with a short right-turn lane compared to the shared-lane situation. Such a capacity enhancement is contributed by both the short-lane usage and the increased saturation flow rate from the single-lane section. An example of a common application of the proposed model is to provide adequate design of the length of the right-turn lane so that the projected traffic demand can be accommodated at an acceptable service level while minimizing the cost associated with the construction of a full or longer right-turn lane.

Traffic detectors support most traffic management applications, so it is important that a detector performs as expected. This study evaluates the performance of four loop sensor models and the remote traffic microwave sensor (RTMS), adding to the body of sensor performance knowledge through the use of new analytical techniques. The study collected contact closure data from all five of the detectors and concurrent video data. Each loop sensor was deployed following Caltrans guidelines for at least 24 h across dual loop detectors in each lane of I-80, north of Oakland, Calif. The research examined various distributions of the individual vehicle actuations from each of the detectors. This exercise found some of the loop sensors locked up and did not provide any data to the controller although they appeared fully functional from the front panel. The sensitivity appears to vary between the RTMS and the loop sensors, as well as from one loop sensor model to the next, which means the occupancy measurements will also change. Detailed analysis of the sensors used the video to manually validate each vehicle passage over extended periods, preselected at random, with the errors classified by type (e.g., nondetected vehicle) and source (e.g., due to a lane change maneuver). As presented herein, the RTMS exhibited problems due to occlusion and reflections, while two of the loop sensors exhibited non-negligible problems. Finally, the methodology used in this paper can easily be extended to validate other detectors and detection technologies.

Single-vehicle crash data for 2000 from Taiwan’s Road Accident Investigation & Reporting System were employed to compare fatality risk factors between non-motorcycle drivers and motorcyclists. On average, motorcyclists had approximately a three times higher fatality risk than non-motorcycle drivers after adjusting for the driving mileage. Two respective logistic regression models for these two categories of drivers indicated that some common features, such as being male, a higher age, and crashes occurring between the hours of 2200 and 0600 revealed a greater likelihood of fatality. On the other hand, the risk discrepancies between these two drivers included the restraint-use effect, speeding, and impairment as the main crash cause, roadway class, and vehicle type. To reduce the high risk of fatality sustained by these two classes of drivers, enhancing the driver’s seatbelt-use rate, the management of running speed, the rider’s risk perceptions, and the road quality and facilities of the lowest roadway class are particularly recommended.

This paper presents a comprehensive approach for establishing the minimum traffic data collection requirements for predicting pavement life within an acceptable error, given a reliability level. Pavement life is predicted for 30 long term pavement performance (LTPP) sites using the NCHRP 1-37A Pavement design guide (PDG). Seventeen distinct traffic data collection scenarios are simulated using extended coverage (i.e., more than 299 days/year) weigh-in-motion (WIM) data obtained from the LTPP database. These scenarios involve combinations of site-specific, regional, and national data, including total truck counts, truck counts by class, and axle load distributions by axle type. Regional data are obtained from LTPP sites in the same jurisdiction as the 30 sites analyzed, using clustering techniques. The PDG software defaults are assumed to be representative of national data. For each scenario involving discontinuous time coverage, the lower range in each of the input elements to the PDG is calculated for confidence levels of 75, 85, and 95%. For each scenario and confidence level, pavement life errors are predicted with respect to the life estimated by the complete extended coverage WIM dataset. Two sources of error are identified: one from specifying the mean value for all traffic input and the other from specifying the lowest percentile for all traffic input simultaneously (i.e., the latter is applicable to discontinuous coverage scenarios only). Overall error is computed by adding the range in the mean of the second error component to the range of the first error component. The results are in the form of plots of pavement life prediction error, versus reliability level, versus traffic data collection scenario. Selecting the first two as a function of the importance of a roadway facility allows identifying the minimum traffic data collection effort required.

An iterative linear stochastic pavement management model is proposed that deploys a nonhomogenous discrete-time Markov chain for predicting the future pavement conditions for a given pavement network. A nonhomogenous transition matrix is constructed to incorporate both the pavement deterioration rates and improvement rates. The pavement deterioration rates are simply the transition probabilities associated with the deployed pavement states. The improvement rates are mainly the maintenance and rehabilitation variables representing the deployed maintenance and rehabilitation actions. A decision policy is formulated to identify the optimal set of maintenance and rehabilitation actions and their respective timings, and to provide the optimal level of maintenance and rehabilitation funding over an analysis period. The nonhomogenous Markov chain allows for a distinct maintenance and rehabilitation plan (matrix) for each time interval (transition). However, the total number of maintenance and rehabilitation variables will substantially increase depending on the length of the deployed analysis period. The resulting optimum model is associated with a nonlinearity order that is equal to the number of time intervals within the specified analysis period. Solving a nonlinear model with a large number of variables is a very complex task. Alternatively, instead of solving a single nonlinear problem, a series of linear problems are formulated and iteratively solved wherein the optimal solution for one problem becomes the input for the next one. The sample results obtained from the iterative linear approach indicate the effectiveness of the proposed stochastic management model in predicting future pavement conditions.

Reflective cracking through jointed concrete pavement overlays has been a persistent problem. Several different rehabilitation strategies have been used in Texas. This paper is a summary of the performance of strategies used in the past 10 years. The performance of the crack-retarding grid has been disappointing as it has been related to several premature failures. Only one project has realized a benefit of the crack-retarding grid, where the reflective cracking was delayed by about 1 year. The writers believe the small openings in the crack-retarding grid and the lack of an effective bond may be the causes of the layer separation. A proprietary crack-retarding asphalt material has been performing well over two years of monitoring. In one experimental project, 100% of the cracks reflected through conventional overlay material in the first year. Both Petromat fabric underseal and crack-retarding asphalt material have been performing satisfactorily to retard reflective cracking. However, there is a large cost difference between these two treatments. Seven experimental treatments on a major section of US 59 were evaluated. The worst-performing section on the US 59 project was the break-and-seat method, which failed due to weak subgrade support. The weak subgrade is unable to support cracked concrete, which leads to a rocking action under traffic loads. It is concluded that for future projects, the break-and-seat method should not be applied on subgrade with a dynamic cone penetrometer penetration rate exceeding 25 mm per blow. A flexible base overlay with thin asphalt surfacing and the Arkansas (large stone) mix have performed well. Flexible base overlays were able to absorb the joint movement and eliminate the reflective cracking. The flexible base should be of top quality with very low moisture susceptibility. In Texas, this involves specifying a Texas triaxial Class 1 material with classification of “good” in suction/dielectric tests. It is also critical to provide an effective seal for the flexible base. A chip seal followed by a thin 75-mm hot mix layer is recommended.