Search

Protected–permissive left-turn (PPLT) and protected only (PO) left-turn signal control modes have been widely used at signalized intersections. The selection between these two control modes is a complicated process in which practitioners need to consider safety and operational impacts. In this study researchers developed analytical models for estimating the operational benefits and the safety risks associated with the use of the PPLT control mode. Evaluation results demonstrated that the proposed models could provide accurate and reliable estimates for the delay reduction and the potential conflicts caused by the use of the PPLT mode. Results of this study will be useful for developing quantitative criteria for the selection between the PO and PPLT modes.

Transportation agencies have increasingly turned to information technology to help address the growing challenges of managing congested urban freeways. Although off-the-shelf information technology products, such as closed-circuit television (CCTV) systems and video image vehicle-detection systems (VIVDS), have proved very useful, their full potential cannot be achieved without integrating the products. The purpose of this research effort was to build on an existing prototype of an integrated CCTV-VIVDS system to provide automatic shoulder event identification functionality. This paper presents the design of the integrated system, provides details on the tools and effort required to support integration of the information technology elements, and describes the results of field testing of the system.

Transportation agencies have increasingly turned to information technology to help address the growing challenges of managing congested urban freeways. Although off-the-shelf information technology products, such as closed-circuit television (CCTV) systems and video image vehicle-detection systems (VIVDS), have proved very useful, their full potential cannot be achieved without integrating the products. The purpose of this research effort was to build on an existing prototype of an integrated CCTV–VIVDS system to provide automatic shoulder event identification functionality. This paper presents the design of the integrated system, provides details on the tools and effort required to support integration of the information technology elements, and describes the results of field testing of the system.

In congestion management, total traffic delay is typically derived based on look-up tables for incident duration, capacity reduction, and frequency that are determinants of total incident delay. The studies that adopted this approach indicate that some factors, such as weather, may not be included in the look-up tables because of their limited size and the lack of rigorous identification of influencing factors to be included in the tables. In addition, the marginal effect of the influencing factors on total traffic delay cannot be analyzed. In this study, statistical models with identified influencing factors for incident duration, lane blockage, and frequency were developed and then integrated into the queuing-based delay equation. Through the development of advanced statistical models, the variables or factors that significantly influence incident duration, lane blockage, and frequency can be identified. When these statistical models are plugged into the queuing-based delay equation, the marginal effect of the identified factors on total delay can then be derived analytically. On the basis of incident data collected in New York City, the proposed approach was demonstrated to be successful.

The CUSUM (cumulative sum of log-likelihood ratio) algorithm is an optimization-based algorithm that is attractive for many applications because it can minimize detection delay and can explicitly incorporate the characteristics of processes before and after changes. One such application is freeway incident detection, where field-measurable traffic-flow parameters are used to flag incidents in real time in an expedient and reliable manner. In the presented study, the special characteristics of traffic processes associated with incidents are incorporated into the CUSUM algorithm for freeway incident detection. In the algorithm evaluation, the most recently developed neural networks are compared with an enhanced CUSUM algorithm. The neural network algorithms are systematically evaluated first among themselves, and then the best of them is compared with the CUSUM algorithm. The results demonstrate that the CUSUM incident detection algorithm can perform better than the neural network algorithms. The neural network algorithm may show inferior performance because it cannot adjust its decision threshold in real time.

A parking information system consisting of a parking information website and roadside displays has been proposed for New York City to alleviate parking difficulties. To justify the implementation of such a system, it is necessary to investigate parking search time and its relationship with parking information. In addition, the parking information items needed for the website and roadside displays and the target markets for this information must be identified. In the investigation, a survey was conducted to collect data on parkers’ demographic and trip characteristics. On the basis of the collected data, the effect of parking information on parking search time was studied, and an ordered probit model was developed. To identify parking information needs, the analysis of variance method was employed to determine the rank of the information items for the website and roadside displays. The profiles of the parkers were also identified for each information item using developed models. The results of the investigation indicated that parking search time is significantly influenced by the amount of parking information parkers possess before starting their trips. Six information items were identified to be the most necessary for the parking information website, and five as most necessary for the parking roadside display. All these information items should be considered when designing a parking information system.