Roundabouts are a widespread form of junction globally, and are particularly common in the UK. This study focuses on the entry capacity at roundabouts under adverse conditions of weather and light in order to determine the extent to which entry capacity is reduced, and the impact that this has on current practical design. So far no specific studies have attempted to quantify this effect. The study was limited to conventional at-grade, normal-size, non-signalised roundabouts in urban areas. Data were collected in 1998 using video capture techniques at four different sites with a total of 13 approaches, comprising 37 entry lanes. The data were transcribed and classified to exclude those minutes of data which did not satisfy the preset traffic criteria, resulting in the extraction and utilisation of 7721 minutes of detailed entry-lane based data. The entry capacities were classified according to whether the conditions were: dry and light; dry and dark; wet and light; and wet and dark. The results identified that wet and dark conditions had a substantial effect on the entry capacity of urban normal-size roundabouts. Entry capacity was found to be reduced by 14% under dry–dark, 17% under wet–light, and 25% under wet–dark conditions. The paper sets out the main practical implications of these findings for design engineers.

The concept of capacity plays a fundamental role within the transportation profession since it is applied in planning, design and operational condition of virtually every road. This paper reports on an in-depth statistical analysis has been carried out for 160 sites across the UK strategic motorway network and 32 sites for trunk roads data to produce a reliable estimation of sustainable lane capacity. Geometric parameters and traffic conditions impacting on capacity have been taken into consideration. The formulation of capacity for motorways and trunk roads has then been produced. The deviation between the link capacities has been found to be significant. It is also found that a number of geometric and locational factors are the explanation to the variations. It is concluded that the average sustainable capacity of a motorway lane is 1780 vehicles/h (2000 passenger car unit per hour with a standard deviation of 130 vehicles/h). The trunk road capacity is evaluated as 1520 vehicles/h with a standard deviation of 170 vehicle/h.

This paper introduces an innovative approach to evaluating the benefits of linked MOVA (Microprocessor Optimised Vehicle Actuation) using a micro-simulation modelling and programming technique. The implementation of linked MOVA at signal-controlled junctions has been found to provide more efficient junction operations by either maximising capacity or minimising delay, depending on the level of congestion. Although vehicle actuation (VA) modelling is commonly available (i.e. bus gating, standalone MOVA and SCOOT), there has been no method for assessing the operational benefits and signal settings of linked MOVA implementation. Using the programming ability within the VISSIM micro-simulation software suite, a precise assessment of the benefits of linked MOVA type VA was undertaken. The signal settings, operational parameters and ‘linking’ of the signal control junctions were set as part of the MOVA implementation in evaluating the operational benefits. A post-implementation evaluation study is presented in which modelled operations replicated the actual operations in line with modelling standards. The model is calibrated and validated using post-MOVA implementation surveys. The results proved a significant operational benefit. On average, delay savings of 19·7% were achieved by the implementation, together with a significant reduction in total stopped delay and number of stops. Although traffic demand remained constant for pre- and post-linked MOVA operations, a 0·5% increase in throughput was observed. Modelling proved an effective method in assessing linked MOVA operations. This technique is now available to linked MOVA users, and can be adapted to other VA-type signal operations in evaluating the coordinated operations, benefits and settings before expensive implementation is undertaken.

The ever‐rising traffic volumes and congestion in cities have long constituted concerns for traffic safety and the economy. Moreover, traffic has been recognised as a significant contributor to emissions leading to serious environmental and public health problems, becoming the greatest contributor to premature deaths. In response to global policies, this paper introduces unique evaluation of road capacity with studied impediment factors, demonstrating the need for better road space allocation. Speed and capacity formulation for each factor is a unique contribution to knowledge as presented. The developed formulation depicts poor road space allocation along Birmingham's routes as speed reduces by 13 km/h, and capacity reduction of 400 vehicles/lane/h. A proven method of integrating microsimulation and environmental assessment tools show that CO2 increases by 18%, NOx by 23%, and PM by 6%, with reduced traffic movement due to poor road space allocation. This analysis bridges the gap in knowledge so far reported on road space allocation, showing evidence of significant contribution to European Union Directive on air pollution exceedance. Lastly, evidence from this analysis is used to develop traffic management proposals for a more sustainable road space re‐allocation. This provides a unique and measurable impact on the environment for the ‘Birmingham Transport Plan’.

Now recognised as a dangerous side effect of increasing human activity and particularly the use of fossil fuels, is the impact on air quality, which has deteriorated considerably in recent times. In particular, the dramatic rise in road traffic has driven up the levels of air pollution in our towns and cities, leading to serious problems for both public health and the environment. To redress this, Environment Policies developed by the World Health Organisation (WHO) and European Commission (EC) have identified clean air as an essential requirement to human health and for the environment-a human right. Therefore, the need for managing emissions resulting from road traffic has seen significant attention. Coincidentally, the increases in the last decades of computational ability has enabled rapid development of transport modelling tools that can be integrated with environmental emissions packages. This has led to the increased ability to test the impact of road emissions on public health and environment. The computational ability to analyse the impact of traffic conditions for both current and forecast operations has enabled engineers to identify improved management and operation techniques for the road intersections with a view to reduce the emissions' impact. This study presents a new and innovative approach to inform such forecast emissions, representing an approach to develop designs that can reduce emissions by linking various software packages as demonstrated at a trial site at a road intersection at Bath, United Kingdom. The technique linked the transport micro-simulation tool VISSIM with the environmental software EnViVer for emissions analysis. The models are also linked to Geographic Information System software, QGIS, to display changing levels of NOx, CO2 and PM (Particulate Matter) under alternative intersection operational management regimes. This approach has enabled three important outcomes: 1) development of a methodology to directly test emissions and inform air quality thresholds using a series of software tools in an integrated manner, 2) enable the investigation of the air quality outcomes for alternative intersection designs and 3) to produce functions for intersection operational parameters that can predict NOX, CO2 and PM savings. The results have demonstrated that the linking of the computational ability of micro-simulation modelling of road intersections with environmental package has been successful in analysis of operations. The 'combined' modelling approach has enabled design development of future intersection operation to with a view to minimising NOX, CO2 and PM. This approach has brought together the crucial traffic parameters of road speed, delay and queuing and related them directly to change in emissions formulation, with the evidenced based prospect of adoption for similar studies in future. To put numbers to the achievement, the results have shown significant achievements for both the NOX level, which is projected to reduce by 14-34%, CO2 by over 13-32% and PM by over 14-26% compa...