A77 and A76 Overtaking Improvements

A77 and A76 Overtaking Improvements

SIAS undertook several traffic and economic assessments on behalf of the Scottish Executive to examine improvement schemes on the A76(T) at Glenairlie and on the A77(T) between Girvan and Stranraer. These include on-line carriageway widening, the provision of climbing lanes and WS2+1. Loch Ryan ports were due for expansion, exacerbating the potential for heavy vehicle platooning and resultant driver frustration caused by the lack of overtaking opportunities. The scheme assessments were conducted in 2005 under the Scottish Executive Multiple Framework Agreement in partnership with Mouchel Parkman Services, Young Associates and Dumfries & Galloway Council.

Microsimulation was seen as the best methodology for identifying the most appropriate remedial measures. S-Paramics has the ability to accurately capture benefits of overtaking improvements resulting from platoon dispersion. All of the schemes identified below would normally be expected to deliver poor rates of economic return if analysed with deterministic modelling systems.

The schemes included identifying overtaking improvements for:

  • A76 Glenairlie
  • A77 Ardwell to Slockenray
  • A77 Park End to Bennane
  • A77 Glen App (carriageway widening)
  • A77 Haggstone (climbing lane)
  • A77 Drummockloch to Innermessan

The S-Paramics output was analysed with the cost benefit economic analysis package PEARS (Programme for the Economic Assessment of Road Schemes), specifically developed by SIAS for use with microsimulation.

The results of the assessments indicated that the combination of S-Paramics/PEARS captured many more of the operational benefits with the schemes returning much improved Net Present Values (NPV) and Benefit Cost Ratios (BCR).

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