Showing papers on "Traffic wave published in 1980"

A local traffic control policy which automatically maximises the overall travel capacity of an urban road network

Abstract: Traffic control strategy is proposed which causes the traffic to be distributed in the spare capacity available on the network so that the traffic uses junction space economically The policy requires only local information such as traffic flows and queue lengths, which can be obtained from vehicle detectors Origin-destination information is not required Consequent changes in the traffic pattern are automatically taken into account It is assumed that traffic signals control all substantially congested junctions, and that, at the most congested junctions, conflicting streams of traffic do not filter through one another The signals must insulate a traffic stream from a conflicting stream by use of non-overlapping greens It is assumed that queue-storage capacity is not limited It is also assumed that a driver only changes his route to a quicker one, and will continue to do so if such a route becomes available

Modeling of Traffic Flow at Signalized Links

Abstract: A rigorous mathematical modeling and analysis of the traffic dynamics downstream of traffic signals and in links between signalized intersections is presented in this paper. The approach taken here is macroscopic in nature and traffic is treated as a continuum fluid. The existence and behavior of shock waves generated periodically downstream of a traffic signal is demonstrated and analytical expressions are derived for describing their propagation along the road. The formation and dissipation of traffic queues at the downstream signal in both time and space is studied and analytical expressions are presented for describing the evolution of the tail end of the queue in time. Due to the large number of possible queue length developments, a methodology for numerical solution to the problem is presented along with numerical examples.

Platoon Dynamics on Signal Controlled Arterials

Abstract: Car path, platoon length, and flow rate equations are developed for the purpose of studying the platoon dynamics at signalized traffic links. The basic modeling is macroscopic in nature and is based on the formation of shock waves generated within the link due to the intermittent service of traffic by the signals. The analysis reveals not only platoon dispersion but also platoon compression, a phenomenon already observed but not previously described mathematically. It is demonstrated that compression does not only occur to platoons entering the link in red but also to those entering in green even in the absence of a downstream signal. Numerical examples are also presented for demonstrating the applicability of the theory.

Noise from urban traffic under interrupted flow conditions

Abstract: Previous attempts to determine an accurate prediction for L10 noise levels arising from interrupted traffic flows have not been entirely successful. Either the prediction equations were too complex or the errors of prediction were too large. This work has attempted to extend these previous studies to identify more accurately the important variables governing the generation and propagation of noise from interrupted flows in urban streets in London and thereby reduce systematic and random errors of prediction. The first stage of this new study concentrated on establishing the effect on L10 noise levels of the traffic related variables by constraining inter-site differences in street layout and other propagation features. In the second stage of the study the propagation of noise from the road source was examined together with reflection effects from buildings and the influence of layout geometry. It was found that L10 was primarily determined by the total volume of traffic and the proportion of different classes of vehicles in the traffic stream. It was found necessary to introduce a three tier classification of the vehicle population rather than two as is common practice when calculating L10 levels from freely flowing traffic. The final prediction equation is expressed in terms of easily obtainable variables and is significantly more accurate than the present Department of the Environment method (calculation of road traffic noise) in predicting noise levels in interrupted traffic flow situations.(a) (TRRL)

Traffic performance on transition between two lane and four lane rural roads

Abstract: This paper describes a study which investigated the changes in traffic mean speed and bunching at transitions between two lane and four lane rural roads. Experiments were conducted using flat metal and rubber detector strips coupled to a microprocessor recorder unit. Changes in traffic parameters with position were found to occur more rapidly on entry to a four lane road than on merging into two lanes. The effects of traffic flow and desired speed were isolated, in order to demonstrate the changes in traffic performance directly due to the transitions in road type. The measurement of bunching was shown to be quite sensitive to the criterion chosen. Since no clear criterion could be established, bunching figures should be regarded as comparative, rather than absolute, values. The aim of the experiments was to provide validating data for simulation programs, and to predict traffic behaviour on passing lanes. The data is somewhat limited, covering only sunday traffic at two sites, over a wide range of flow rates. The influence of trucks on these results is not known. The findings may be of interest in the study of rural transition points and temporary detours.

Some errors in macroscopic traffic models based on car following models

Abstract: The macroscopic traffic flow models developed from the car following models of Gazis et al. (1961) are shown to have a flaw in that they do not meet certain of the boundary conditions that researchers have said that they do. This does not affect many existing models but, nevertheless, should be cleared up.