824 research outputs found
A critical review of the standards and design processes for motorway diverges in the UK
No full textThis paper contains a critical review of design standards for motorway diverges in the UK over the last 40 years. These standards have been progressively updated at regular intervals and their evolving nature has been assessed. Most changes have been minor as a result of changes to traffic flow, driver behaviour or vehicle performance. A brief comparison has also been made between standards for diverges in the UK and those in other selected EU countries. This paper particularly focuses on the diverging flow-region diagram contained in the latest Government Standard TD22/92 ‘The Layout of Grade-Separated Junctions’. This diagram is used by traffic engineers as a tool in order to select the most appropriate diverge layout for a particular site. The historical background leading to its derivation is reviewed along with a discussion of comments made by five practicing traffic engineers as to its effectiveness and usage. These comments have been used along with other analysis to make recommendations as to how the diagram should be interpreted and how it could be improved
The 'tiger-tailed' ghost island layout gets favourable reception
No full textThis article discusses the success of the new Ghost Island diverge layout, which is an alternative design incorporating a wide 'tiger-tailed' ghost island painted area. It enables drivers to leave the motorway either at the first exit point entering slip lane 1 or at the second exit point entering slip lane 2. It has performed successfully as an anti-swooping measure at three UK sites monitored by the Transport Research Laboratory (M20/M26 in Kent, M6 J4a near Binningham and M27/M3 near Southampton). Swooping is defined as vehicles cutting directly from lanes 2 or 3 or the maintine into the slip road in order to leave the mainline, typically within 500m of the diverge point. In order to comb and confirm the objective data collected from the TRL video trial at the M27/M3, a subsequent questionnaire survey was carried out between November 2000 and March 2001 on 54 drivers familiar with the Before and After layouts. Results showed a favourable response to the new layout in terms of drivers experiencing smoother flow, a reduction in last minute lane changes and easier access to the M3. Recommendations were made with regards to incorporating these designs as standard diverge layouts as well as consulting drivers more extensively before any major new motorway junction schemes are implemented
A review of anti-swooping trials
No full textThis report provides a summary of the TRL trials, conducted between 1995 and 2000, which have attempted to combat the problem of 'swooping' at diverge areas. Two different approaches to solving this problem have been employed within this study; new lane separation markings including anti-swooping diamond shaped markings at junction 6 of the M6 motorway diverge and 'ghost' island diverge layouts. The trials have shown that reducing swooping manoeuvres during peak periods increases both the capacities of the mainline and of the slip road through the smoothing of vehicle flows through the section. The 'ghost' island diverge layout has been particularly successful in modifying diverging driver behaviour and has been used in both auxiliary lane and lane drop layouts. The study has also highlighted that for a scheme to be successful the modified layout should be accompanied by appropriate signing to inform drivers of the expected behaviour. The promotion of the scheme through local media prior to the installation, encourages regular users of the diverge to adapt their behaviour in order that the expected benefits can be experienced
Capacity implications of advanced stop lines for cyclists
No full textAn investigation of the capacity implications of installing Advanced Stop Lines (ASLs) has been carried out by TRL Limited as part of a project entitled Cycling Facilities and Engineering, commissioned by the Charging and Local Transport Division of the Department for Transport. The study included a review of previous research into ASLs in the UK and in the Netherlands; an examination of the theoretical capacity implications of installing ASLs using OSCADY (Optimised Signal Capacity and Delay) the signal-controlled junction modelling computer programme and saturation flow formulae; 'before' and 'after' video surveys of modified junctions at four sites in Guildford, Surrey, and questionnaires to examine the attitudes of cyclists. While cyclists generally thought that the ASLs were safer and easier to use than unadapted junctions, concerns were expressed that some drivers did not comply with the new layout. Changes in the length of time between green signals or a longer minimum green time may be required in some circumstances. At the two sites where the number of traffic lanes remained the same there was a slight increase in saturation flow, but at the two sites where a traffic lane was removed large reductions in saturation flow were observed. This report of the study concludes with several recommendations.<br/
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