Traffic congestion

About: Traffic congestion is a research topic. Over the lifetime, 16826 publications have been published within this topic receiving 235654 citations. The topic is also known as: traffic jam & traffic snarl-up.

A multivariate state space approach for urban traffic flow modeling and prediction

Abstract: Urban traffic congestion is one of the most severe problems of everyday life in Metropolitan areas. In an effort to deal with this problem, intelligent transportation systems (ITS) technologies have concentrated in recent years on dealing with urban congestion. One of the most critical aspects of ITS success is the provision of accurate real-time information and short-term predictions of traffic parameters such as traffic volumes, travel speeds and occupancies. The present paper concentrates on developing flexible and explicitly multivariate time-series state space models using core urban area loop detector data. Using 3-min volume measurements from urban arterial streets near downtown Athens, models were developed that feed on data from upstream detectors to improve on the predictions of downstream locations. The results clearly suggest that different model specifications are appropriate for different time periods of the day. Further, it also appears that the use of multivariate state space models improves on the prediction accuracy over univariate time series ones.

The scoot on-line traffic signal optimisation technique

Abstract: Many large cities have, or plan to have, urban traffic control (utc) systems that centrally monitor and control the traffic signals in their jurisdiction. The present generation of utc systems usually co-ordinates the signals on fixed-time plans, which consist of sets of timings that determine when each signal turns red and green. The plans are precalculated to suit average conditions during each part off the day (e.g. A.M. peak) and do not respond to variations in flows in the network. Since 1973 the UK Transport and Road Research Laboratory has been researching a vehicle responsive method of signal control called SCOOT (split, cycle and offset optimisation technique). Research was carried out in Glasgow by a small team from TRRL and the Ferranti, GEC and Plessey traffic companies, with assistance from Strathclyde Regional Council. In 1976 the success of the research phase led to a development project between the departments of transport and of industry and the three traffic companies. TRRL continued research into SCOOT and in 1979 carried out a full-scale trial of SCOOT in Glasgow. As part of the development project, and with the co-operation of West Midlands County Council, SCOOT was installed in Coventry. A further full-scale trial of the developed system was carried out in 1980. This paper describes the SCOOT system and the results of the trials which compared SCOOT with up-to-date fixed-time systems. It is concluded that SCOOT reduced vehicle delay by an average of about 12 percent during the working day. The surveys demonstrate that scoot rapidly adapts to unusual traffic conditions as well as to the usual variations in demand that occur throughout the day and night. It is an important benefit of SCOOT that there is no need to periodically prepare new fixed-time plans and that the signal timings are automatically kept up-to-date. The traffic model in SCOOT provides real-time information on flows and queues and is likely to be a key element in the development of new traffic management strategies that make the best overall use of roads in urban areas. This paper is a shortened version of TRRL Report LR 1014 (see TRIS 348845). This paper was presented at the IEE's Conference on Road Traffic signalling, Londong, March 1982. See also TRIS abstracts 368871 and 368872. (TRRL)

Modelling lane changing and merging in microscopic traffic simulation

Abstract: This paper introduces Simulation of Intelligent TRAnsport Systems (SITRAS), a massive multi-agent simulation system in which driver-vehicle objects are modelled as autonomous agents. The simulation outputs can be used for the evaluation of Intelligent Transport Systems applications such as congestion and incident management, public transport priority and dynamic route guidance. The model concepts and specifications, and the first applications of the model in the area of incident modelling in urban arterial networks were described in previous publications. This paper presents the details of the lane changing and merging algorithms developed for the SITRAS model. These models incorporate procedures for ‘forced’ and ‘co-operative’ lane changing which are essential for lane changing under congested (and incident-affected) traffic conditions. The paper describes the algorithms and presents simulation examples to demonstrate the effects of the implemented models. The results indicate that only the forced and cooperative lane changing models can produce realistic flow-speed relationships during congested conditions.

Some developments in equilibrium traffic assignment

Abstract: A network optimization problem is formulated which yields a probabilistic equilibrated traffic assignment incorporating congestion effects and which as a special case, reduces to a user optimized equilibrium solution. In the resulting model, path choice is determined by a logit formula in which path costs are functions of the assigned flows. The article also demonstrates the similarity between some fixed demand incremental methods of traffic assignment and the minimization problem associated with computing the user equilibrium assignment.