Visibility Splays

This article was published in 2001, in Newsletter 36.

Image as described adjacent
The Y Dimension is the distance along the road where the cyclist can see and be seen. This diagram is freely copied from one in the Scottish Executive’s Cycling by Design, with permission – the original is crown copyright

Many publications detail the visibility splays or sight lines required to make roads safe for motoring. In essence it must be possible to see and be seen. I have a 30 year old publication Road Accidents: prevent or publish which states that improving visibility is one of the most cost-effective methods of reducing accidents at junctions.

Unfortunately these hard learnt lessons seem to have been almost forgotten when it comes to shared use paths and cycleways. I say ‘almost’ because careful reading of ‘Design Bulletin 32: Roads and Footpaths in Residential Areas’ shows it does include shared use paths in section 3.68 where it states: ‘the Y dimension where a driveway meets a carriage way or shared surface should be set out as in para. 3.64 ‘. Hence for a route where cyclists may do 20 mph, visibility is required for some 30 metres.

Better Guidance is given in the Scottish Executive Cycling by Design for which there appears to be no ‘English’ equivalent.

Section 4 ‘Geometric Design’ has similar tables and diagrams which refer specifically to cycle routes.

Can we hope that those responsible for designing our much used facilities will take some note of these published guidelines?

Jim Chisholm