Modelling unsignalised traffic flow with reference to urban and interurban networks

A new variant of cellular automata (CA) models is proposed, based on Minimum Acceptable Space (MAP) rules, to study unsignalised traffic flow at two-way stop-controlled (TWSC) intersections and roundabouts in urban and interurban networks. Categorisation of different driver behaviour is possible, based on different space requirements (MAPs), which allow a variety of conditions to be considered. Driver behaviour may be randomly categorised as rational, (when optimum conditions of entry are realised), conservative, urgent and radical, with specified probabilities at each time step. The model can successfully simulate both heterogeneous and inconsistent driver behaviour and interactions at the different road features. The impact of driver behaviour on the overall performance of intersections and roundabouts can be quantified and conditions for gridlock determined. Theorems on roundabout size and throughput are given. The relationship between these measures is clearly non-monotonic. Whereas previous models consider these road features in terms of T-intersections, our approach is new in that each is a unified system. Hence, the relationship between arrival rates on entrance roads can be studied and critical arrival rates can be identified under varied traffic and geometric conditions. The potential for extending the model to entire urban and interurban networks is discussed

Traffic noise monitoring at road intersections in urban settlement: Case study of Ramat Park Benin City

Ramat Park is one of the popular Parks in Benin City which is in form of a roundabout connecting traffic from Benin City to the North and Central part of the state including Delta state. In most cases, especially on market days, there is a gridlock within the park which necessitates the uncontrolled honking of horns and emission of other vehicular noise in a bid to checkmate reckless driving. Traffic noise was measured within a period of one month using digital noise meter at 10m away from the source of the noise and about 1.2m above ground level. Two traffic models (Rahul Singh Equation and Calixto Model) were used to calculate the vehicular noise level and the values obtained correlated well with the observed values. The plots of the measured and computed noise levels gave Root Mean Squares (RMS) of 0.776 and 0.839respectively.This indicates that the pattern of the scattered plot is narrow and there is a strong relationship between both computed and measured noise. It was therefore concluded that indiscriminate and reckless activities of drivers (especially commercial bus drivers) were responsible for the noise emission while enforcement of traffic laws in the state and relocation of the motor park close to the square were recommended control measures for noise reduction. http://dx.doi.org/10.4314/njt.v35i4.

Efficiency of Roundabouts as Compared to Traffic Light Controlled Intersections in Urban Road Networks

Evaluating the performance of a multi-lane intersection is important to identify the best scheme as congestion is becoming a worldwide serious problem. A Multi-stream Minimum Acceptable Space (MMAS) Cellular Automata (CA) model is used for the simulation of vehicular traffic at double-lane roundabouts and cross intersection. Comparison is made between roundabouts with traffic light and without traffic light and signalized intersections on the basis of their performance to simplify traffic congestion. Computer simulations are used to propose critical arrival rates to separate between the three mentioned modes to decrease congestion at intersection points.Keywords: Traffic flow, Roundabout, Throughput, Multi-stream Minimum Acceptable Space, Cellular Automat

Estimating and exploiting the capacity of urban street networks

The paper deals with the problem of estimating and exploiting traffic capacity of different road elements (link, nodes, network) and presents the results obtained by performing a systematic investigation of the role that the parameters of a microscopic simulation model play on the macroscopic representation of different road elements. An analysis of traffic parameters has been performed using a microsimulation software package to identify the most important parameters affecting the arterial capacity and to calibrate driver's behavior models through macroscopic traffic observations

Un modèle d'automate cellulaire pour le trafic urbain avec plusieurs ronds-points

International audienceUrban transportation with multiple roundabouts is facing significant challenges such as traffic congestion, gridlock and traffic accidents. In order to understand these behaviors, we propose a two-dimensional cellular automata (CA) model, where all streets are two-way, with one lane in each direction. To allow the turning movement, a roundabout is designed for each intersection where four roads meet. The distance between each pair of roundabouts is configured with the parameter K while the turning behavior of drivers is modeled by a parameter γ. To study the impact of these different parameters on the urban traffic, several traffic metrics are considered such as traffic flow, average velocity, accident probability and waiting time at the entrance of roundabout. Our simulation results show that the urban traffic is in free flow state when the vehicle's density is low enough. However, when the density exceeds a critical density ρ c , the urban traffic will be in gridlock state whenever γ is nonzero. In the case where γ = 0, the urban traffic presents a phase transition between free flow and congested state. Furthermore, detailed analysis of the traffic metrics shows that the model parameters (γ, K) have a significant effects on urban traffic dynamics

SIGNAL SETTINGS SYNCHRONIZATION AND DYNAMIC TRAFFIC MODELLING

The object of the paper is to investigate the effect of signal synchronization on the traffic flow patterns on the network and validate results of synchronization problem in signal setting design. A platoon based traffic model is applied to solve both one-way and two-way synchronization problems in under-saturated conditions. Assessment of results through dynamic traffic assignment model shows that solution found is rather robust and, if more traffic is attracted by the improved arterial performance, larger benefits can be achieved on the whole network. A specific analysis has been conducted to point out the representation of queue propagation and the gridlock phenomenon

Broadening Understanding of Roundabout Operation Analysis: Planning-Level Tools and Signal Application

In United States, roundabouts have recently emerged as an effective and efficient alternative to conventional signalized intersections for the control of traffic at junctions. This thesis includes two investigations related to the operations of roundabouts. The first investigation examines the ability of a planning-level tool (the critical sum method) to serve as an indicator variable for the results of the Highway Capacity Manual’s average delay per vehicle measure for a roundabout facility; to what extent do the results of one predict the results of the other? The critical sum method was found to accurately predict the HCM average delay per vehicle for low-volume conditions, approximately up to an average delay of 15 seconds per vehicle, but the tool was found to provide inaccurate predictions for higher volume conditions. The second investigation looks at the potential of metering signals on a roundabout facility to transfer excess capacity from a low-volume approach to an adjacent higher-volume approach. The analysis indicated positive results for the theoretical benefits of the metering signal when only placing simulated traffic on two of the approaches, but the results were not duplicated when analyzing more-realistic volume scenarios with traffic on all four approaches. Advisor: John Sangster

Urban Traffic Congestion and Its Attendant Health Effects on Road Users in Ado-Ekiti, Nigeria

This study focused on urban traffic congestion on road users in Ado-Ekiti,Nigeria. It looked critically at the problems, causes and possible remedialmeasures to urban traffic congestion within the study area. Data for thisstudy were collected from primary sources, through the administration ofquestionnaires and personal observation. Two sets of questionnaires weredesigned for this research. One set for members of the National Union ofRoad Transport Workers (NURTW) within the study area, (100). Another setof questionnaires were randomly administered on other categories of roadusers (pedestrians, motor cyclist and passengers) within the study area,(100). Results from this study showed that physical break down, mental effect and psychological effects were the major effects of road trafficcongestion on human health in the area. This study therefore recommended that, other alternative transportation system, proper city planning and the construction of interchange and overhead bridges were the panacea to urban traffic congestion in the area