Visibility is the most common reason an access is questioned. The numbers look technical, but the idea is simple: can a driver waiting to pull out see far enough to do it safely?
The two measurements
- The X distance is how far back from the edge of the road the driver sits. 2.4 metres is normal. Manual for Streets allows 2.0 metres in some very lightly used, slow-speed situations.
- The Y distance is how far along the road the driver needs to see. It depends on how fast approaching traffic is travelling.
The triangle between them is the visibility splay. It has to be kept clear of walls, hedges, parked cars and anything else that blocks the view, permanently.
Where the numbers come from
On most streets in built-up areas, councils use Manual for Streets. Its stopping sight distances include around 25 metres at 20mph and 43 metres at 30mph. On faster roads, councils may use the Design Manual for Roads and Bridges, which gives longer distances.
Speed limit or actual speed?
Councils usually ask for splays based on recorded speeds, normally the 85th percentile speed from a survey, adjusted for wet weather where needed. If traffic travels slower than the limit, a survey can justify a shorter splay. If it travels faster, you need to know early.
When they can flex
- Measured speeds below the limit
- A lightly used access in a slow-speed street
- Moving the access to a better point along the frontage
- Physical changes that slow traffic, agreed with the council
The land question
A splay must cross land you control or public highway, and stay clear for good. If it crosses a neighbour’s hedge or wall, you will need their agreement, usually secured legally. Check this before you buy a site, not after.
General information, not advice on a specific site. Policy and guidance correct as of October 2026.