Showing papers on "Traffic wave published in 1986"

Dynamic Model of Peak Period Traffic Congestion with Elastic Arrival Rates

Abstract: The paper develops a dynamic model of peak period traffic congestion that considers a limited number of bottlenecks. The model predicts the temporal distribution of traffic volumes with an elastic demand model. In response to changes in the traffic conditions travelers can switch to a different mode, divert to an alternate route, or shift the trip forward or backward in time to avoid a long delay. A simple example would be the case of two parallel routes with travelers jointly selecting route and departure time. The choice of route and mode are dependent on travel times and travel costs. The choice of departure time is based on the trade-off between travel time and schedule delay which is the difference between the actual and the desired arrival times. The delays at the bottlenecks are modeled with a deterministic queueing model that determines waiting time as a function of the length of the queue at the time of arrival at the bottleneck. The day to day adjustment of the distribution of traffic is derived...

The prediction of saturation flows for road junctions controlled by traffic signals

Abstract: DESCRIBES A COMPREHENSIVE PROGRAM OF MEASUREMENT OF SATURATION FLOW AT TRAFFIC SIGNALS AND THE DEVELOPMENT OF PREDICTION FORMULAS WHICH UPDATE THOSE IN: TRAFFIC SIGNALS BY F.V. WEBSTER AND B.M COBBE -- LONDON : HMSO, 1966

Traffic congestion catastrophes

Abstract: Authorities in both traffic engineering and driver behaviour have empirical evidence that drivers' behaviour differs when journeying in free moving traffic or stop and go situations. Catastrophe theory provides a unified approach to explain the sudden change in traffic stream behaviour. In addition, the theory indicates that ranges of traffic break‐down may be determined from a suitable mathematical description of the surface and the resulting cusp‐catastrophe.

Development and validation of a car following model for simulation of traffic flow and traffic wave studies at bottlenecks

Abstract: A car following model, CARSIM, is developed and validat­ ed under various traffic conditions at microscopic and mac­ roscopic levels. It realistically simulates normal flow as well as stop-and-go operations. CARSIM provides a margi­ nally safe following distance for all vehicles. It uses variable reaction times for drivers, and takes into account the start-up delay of the drivers. CARSIM may be used as a single regime model or as a dual regime model. Different maximum deceleration rates one for before the disturbance and another for after the disturbance is used to reflecte the slower reaction of drivers to accelerate than to decelerate. A 2 second start-up delay is suggested for the stopped cars. When the flow is not in the steady state condition, the time headway computed as the recipro­ cal of volume is not equal to the mean of vehicles' head­ way . After an extensive validation the model is used to study the propagation of traffic waves at a microscopic level and the effects of mainline traffic control on congestion

Traffic operation on busy two-lane rural roads in the netherlands

Abstract: In the framework of updating standards for describing the quality of traffic flow on two-lane rural roads, research into the behavior of the traffic flow on relatively high-volume roads was carried out. Presented in this paper are findings about the relation between the volume and traffic composition as explanatory factors for speeds, headways, and platooning. It was found that mean speed was only marginally influenced by volume and truck percentage, whereas the standard deviation of speeds decreased substantially with increasing volume. An exponential tail model for headways, large enough to be relevant for passing opportunities, was used and its parameters were successfully related to volume. This model fits reality much better than the assumption that headways have a negative exponential distribution, which leads to severe underestimation of passing opportunities. Simple models were developed that relate the proportion of vehicles following in a platoon and the maximum platoon length in 5 min to volume and truck percentage. A comparison is made with results in the proposed Chapter 8 on Two-Lane Highways of the 1985 Highway Capacity Manual.

On-line estimation of platoon delay

Abstract: The operation of an area traffic control system can be improved if platoon delay, queue lengths, journey times and other performance indices are automatically monitored online as an integral part of the system operation. This paper identifies delay as an appropriate performance index for system evaluation. It proposes a scheme by which system performance can be monitored with stop line detectors. Link flows are first estimated by a recursive least squares algorithm from stop line departure flow profiles collected upstream. Platoon delay is then estimated from the predicted arrival and the actual departure flow profiles. The scheme introduces modelling into a control system such as scats which uses stop line detectors. It should be useful for optimal selection of offsets. Results based on simulated data indicate that the scheme is feasible (a).

Congestion-based control scheme for closely spaced, high traffic density networks

Abstract: The development and field testing of a traffic control policy designed for congested conditions in the high-density sectors of the Manhattan central business district (CBD) are described. Rather than providing progressive movement in the conventional sense, the primary objective of this control policy is to minimize the frequency and extent of intersection spillback. In the Manhattan CBD, queues develop along the cross streets; these queues often spill back into the upstream intersections, physically blocking the movement of traffic along the north-south arterials. The traffic control policy described yields signal timing for the one-way cross streets that exhibit a backward progression and flared green times that increase in the direction of traffic flow. The arterial traffic is serviced by a signal-timing pattern that exhibits zero relative offsets. The NETSIM traffic simulation model was used to test different concepts during the development phase of the effort. The new policy was then compared with the existing timing plan, by using NETSIM, and the results indicated that the number and duration of spillback blockage were markedly decreased, with a concomitant reduction in vehicle travel time and number of stops, coupled with an increase in vehicle trips serviced. A before-and-after field study yielded similar results, with the new policy providing a 20 percent reduction in overall travel time.

Traffic congestion-relief device for highways

Abstract: The invention relates to the problem of wasted fuel when motor vehicles are in traffic jams, the reduction of the environmentally damaging engine exhaust gases and noise emissions. Remote-controllable traffic signals are installed from the point at which the traffic is impeded, counter to the direction of travel, at approximately 200-metre intervals from one another along the traffic jam and are connected to sensors in the vicinity of the traffic jam and at the point of obstruction by cables. If the flow of motor vehicles slows down to congestion speed or to a standstill, this is registered by the sensors and the first traffic signal switches to red (stop). The line of vehicles is stopped. After the red signal the vehicles move on. A large gap in the vehicles is produced. After a time interval which is determined by the flowing away of the vehicles in the section of the obstruction, the red signal is switched to green and at the same time the next traffic signal is remote-controlled to red. The vehicles between them now drive off and through the point of obstruction. The next group of vehicles follows and so on. If the last or first traffic signal shows green, all the vehicles held back before them drive on and through the point which is obstructing the traffic. If the vehicles back up again as far as the first signal or sensor, the group-based congestion relief starts again automatically from the beginning. (As long as the congestion relief device is in operation, all the signal generators, except for the operating ... Original abstract incomplete.

Inflow control on expressway considering traffic equilibria

Abstract: When expressway and roads coexist, it is necessary to establish a reasonable traffic share between them. It may be practiced by the regulation of toll-rate of expressway. But at an occasional traffic congestion, the reasonable share is disturbed, so that some traffic control means should be taken. In this paper, we deal how to control inflows on expressway, from a viewpoint of the optimal share between expressway and roads. The minimization of total travel cost in a system is aimed under traffic equilibrium conditions. The problem is formed as a two-stage programming model, and a simple example solving the problem is showed.

Predicting time-dependent distributions of queues and delays for road traffic at roundabouts

Abstract: Vehicle queues and delays at busy road junctions have to be treated time-dependently when the traffic demand and the available capacity are approximately equal. Existing methods allow the queue length at a given time to be directly estimated as an average over all possible evolutions of the queueing system consistent with the given initial conditions and the time-dependent arrival and service rates. The paper describes the development of methods to predict the underlying distributions. Estimates of the variance and the overall frequency distribution for queue length and delay are obtained by simulating an M/M/1 queueing model with parameters varying with time. Predictive models are developed to represent the simulation results. They require as input values of parameters describing the duration of the peak and the time-average traffic intensities and capacities.