The combined application of centerline and shoulder rumble strips is intended to reduce the frequency of crashes by alerting drivers that they are about to leave the traveled lane. To date, this combination treatment has not been rigorously evaluated with a multistate database. To fill this void, this study evaluated treated two-lane rural road locations in three states. To account for potential site selection bias, an empirical Bayes (EB) before-after analysis was conducted. The combined results for all states indicate statistically significant crash reductions for all crash types analyzed. The crash type with the smallest crash modification factor (CMF) (i.e., the greatest crash reduction) is head-on with a CMF of 0.632 (i.e., a crash reduction of 36.8%). For run-off-road, head-on, and sideswipe-opposite direction crashes combined (i.e., lane departure crashes), the estimated CMF is 0.733. Benefit:cost (B:C) ratios were estimated to range from 28.2 to 67.7, depending on the treatment cost and service life assumption.

A model-based scheme has been developed in this paper to estimate the number of vehicles in queue and the total delay, which are typical measures for characterizing a signalized intersection. The estimation was first carried out by using the input-output and queue accumulation polygon methods. These were evaluated by using data from two instrumented intersections in the city of Lincoln, Nebraska. However, the estimates did not agree well with the actual data primarily because of the errors in counts obtained from the automated detectors. Hence, an analysis of the characteristics of the errors was carried out. A model-based estimation approach using the Kalman filter was then developed. Suitable modifications were further applied to the estimation process by incorporating calibration constants for particular site/traffic conditions in the Kalman filter estimation scheme. The results obtained were promising, indicating that the scheme could be used for performance analysis of signalized intersections with automated detectors.

Multiple applications of travel time data collection based on the reading of time-stamped media access control (MAC) addresses from Bluetooth-enabled devices have been reported in the literature, and commercial data collection units (DCUs) have been developed and deployed. One characteristic of Bluetooth-based travel time data obtained for travel time sample-generation purposes is that a MAC address is typically read multiple times as a vehicle containing the Bluetooth device travels within the length of road covered by the DCU’s antenna. Such data records of the same MAC address will have different timestamps and received signal strength levels. If the DCUs are installed at arterial intersections to collect travel time samples, this characteristic of MAC address data collection may also be used as the basis for estimating intersection performance. In this research, the use of the time/duration information present in the MAC address data to estimate intersection performance measures is investigated. Estimates of average control delay and approach delay are computed for a real intersection and are shown to track well with intersection-to-intersection travel times.

The selection of the macrolocation of new high-speed rail (HSR) systems during the planning stage affects the associated infrastructure costs. The process is influenced by the complex interaction between the HSR alignment, the technical solutions, and the characteristics of the deployment site, subject to layout restrictions. Decision support systems for the optimization of the HSR alignment are developed for addressing the requirements of large and complex real projects. The formulation includes costs, geometric constraints, connection requirements, and consideration of natural barriers such as protected land use and bodies of water, ubiquitous in real projects. The simulated annealing algorithm is implemented to address challenges of real problems and solve the optimization model. The approach is applied to a Portuguese HSR case. The solution obtained optimizes its alignment by minimizing the construction costs, consistent with existing projects worldwide, and complying with location, geometry, and land-use restrictions. The approach is not case specific and can be used to systematically study trade-off opportunities and support decision making in similar planning problems. Alternative solutions can be generated based on different judgments on the trade-offs.

The fundamental purpose of any construction specification is to ensure the expected long-term performance of the final product. A construction project that fails to meet the required quality level should always result in reduced payment to the contractor in order to recover the future costs that the highway agency will incur for additional maintenance. However, a superior-quality project must be rewarded based on actual savings to the agency that correspond with the improvement in performance due to higher construction quality. Performance-related specification (PRS) incorporates the economic implications associated with superior or inferior pavement construction practices. In general, earlier PRS development studies were based on performance data collected from either pilot pavement construction projects or models built based on experimental pavement sections. This study primarily focuses on constructing a pay adjustment framework utilizing field performance data and actual quality control measurements obtained during road construction projects. An econometric modeling approach for establishing the relationship between quality control parameters and the corresponding pavement performance (in terms of early deterioration rate) is proposed. Laboratory density of plant-mix, placement density of compacted pavement, and as-constructed ride quality are identified as performance-sensitive parameters. A performance-related, pay adjustment scheme that is governed by performance-sensitive quality control parameters is also developed.

This study investigates the roundabout as a system in which the interaction of inflow, outflow, and circular flow are analyzed. Developed based on the concept of Macroscopic Fundamental Diagram (MFD), the macroscopic properties of the roundabout system are estimated by fitting traffic data into several traffic-stream models. The capacity and optimal density are derived from regression fitting. A novel control strategy that aims to regulate the approach inflow in order to maintain the average density on the circular segment at an optimal density is then proposed. It decides on the approach that needs to be restricted based on the circular segment density (i.e., congestion level) and the origin-destination demand pattern to prevent gridlock. A case study of a two-lane roundabout in Selangor, Malaysia is developed in a microscopic simulation environment to study the roundabout system properties and to test the effectiveness of the proposed control strategy. Results show that the Greenshield model has the best fit in describing the roundabout system properties. The proposed control strategy is effective in reducing system travel time and increasing throughput, especially during medium to high levels of demand. In addition, the sensitivity analysis reveals that the effectiveness is sensitive to the parameter setting, roundabout geometry, as well as traffic condition and origin-destination pattern.