Stopping sight distance and forward visibility.
Stopping sight distance, visibility splays and forward visibility worked out properly for your site, using measured speeds where they help.
Also known as: stopping sight distance, SSD, forward visibility, visibility splay, y distance
What’s included.
Stopping sight distance (SSD) is the distance a driver needs to see ahead to stop safely. It sets the y distance of a visibility splay and the forward visibility needed around bends. Manual for Streets gives values for streets and lower-speed roads; DMRB CD 109 for higher-speed roads.
- Speed surveys and 85th percentile speeds
- SSD using Manual for Streets or DMRB
- Visibility splays at accesses and junctions
- Forward visibility on bends and internal roads
- Visibility over land you control
- Relaxations and how to justify them
Straightforward, proportionate, agreed early.
Measured, not assumed
Where traffic is slower than the limit, recorded speeds usually justify a shorter splay.
The right method
Manual for Streets where it applies, which typically gives shorter distances than DMRB at the same speed.
Deliverable
Splays drawn over the highway or land you control, so they can be kept clear for good.
Questions we get asked
What visibility is needed at 30 mph?
Under Manual for Streets, a typical splay on a 30 mph road is 2.4 m by 43 m, but it depends on the measured speeds and the council’s standards.
What is forward visibility?
The distance a driver can see ahead along the road itself, for example around a bend. It should be at least the stopping sight distance.
Can a splay cross a neighbour’s land?
Only if it can be secured and kept clear, which is rarely straightforward. We look for a design that avoids it.
Often needed alongside.
Last reviewed October 2026 by Ripple Development Planning. Policy and guidance change; for advice on a specific site, send us the details.
From our insights.
Need help with stopping sight distance and forward visibility?
Send us the location and what's proposed. We'll tell you what it needs, with a fixed fee.