Highway safety refusals and visibility splay evidence
Visibility splay requirements follow recorded vehicle speeds, not the posted limit. Here is the evidence that answers a highway safety reason for refusal on a small residential access.
A highway safety reason for refusal almost always comes down to one of three things: you cannot see far enough when pulling out, the access geometry is wrong, or the traffic the scheme generates makes an existing problem worse. Of those, poor visibility is the most common on small sites and the most winnable, because the requirement is set by measurable evidence rather than opinion. Get the speed survey right and the splay requirement often drops to something the plot can deliver.
The Framework has not changed its position. The NPPF (August 2026 edition) keeps the test that development should only be prevented or refused on highways grounds where there would be an unacceptable impact on highway safety, or the residual cumulative impacts on the road network would be severe. That is a high bar, and a consultee objection is not the same thing as meeting it.
What the highway authority objection usually says
The standard form runs: the proposed access fails to provide visibility splays of 2.4 metres by 43 metres in accordance with adopted standards, and would therefore be detrimental to highway safety. Sometimes the y distance is 90 metres because the officer has taken the road as a 40mph route without checking. Sometimes there is no measurement at all and the objection rests on a site visit impression.
Read the consultation response as evidence, and test each figure in it. Which document sets the standard, and is it the adopted local plan, a county design guide or an internal note. What speed was assumed, and where did that speed come from. Whether the splay was measured from the correct set-back and to the correct height.
An objection that cites a standard without naming the source is answerable. One that attaches a marked-up plan and a speed survey is a different problem, and worth reading properly before you argue with it.
Measuring a visibility splay properly
A splay has two dimensions. The x distance is the set-back from the edge of the carriageway to the driver's eye, conventionally 2.4 metres for a private drive serving a small number of dwellings. The y distance is the stopping sight distance along the road in each direction, taken from that eye position.
Manual for Streets sets stopping sight distances for lower speed streets, around 25 metres at 20mph and 43 metres at 30mph, with larger values as speeds rise. Check the current edition of the guidance, because the figures and the approach to measurement have been revised and highway authorities do not all update their standards at the same time.
Three measurement points decide whether the splay works:
- Eye height, taken over a range from about 1.05 metres to 2.0 metres, so a low wall may not obstruct while a fence does.
- Object height, which for an approaching vehicle is measured down to 0.6 metres and for some authorities to 1.05 metres.
- The near edge of the carriageway rather than the kerb line where there is a wide verge.
Measure on site with a laser and photograph the sight line from the driver's position at the correct height. A splay drawn on a plan and never checked on the ground is where cases get lost, because the plan does not show the hedge that has grown 600 millimetres into the verge.
Recorded speeds against the posted limit
This is the single most useful piece of evidence on a rural or edge-of-village access. Splay requirements follow actual vehicle speeds, not the sign on the pole. A 60mph national speed limit lane where recorded speeds sit in the low thirties does not need a 215 metre splay, and an authority that insists on one is applying a standard to a road it has not measured.
Commission an automatic traffic count over seven consecutive days in a neutral period, positioned clear of the junction so that turning movements do not depress the readings. The output you need is the 85th percentile wet weather speed in each direction, which is the convention used to set sight distances. Avoid school holidays, avoid August and December, and record the exact position of the tubes on a plan.
Illustrative example: a two dwelling infill on a lane signed at 60mph, where the highway authority sought 2.4 by 160 metres. A seven day count returned 85th percentile speeds in the mid thirties, supporting a y distance closer to 60 metres, which the frontage could deliver after lowering a section of hedge. The objection was withdrawn and the access approved with a splay condition. The figures are illustrative and used to show the method.
A count costs a few hundred pounds. Set against a refusal, an appeal and a year of delay, it is the least costly evidence on the project, which is why a Transport Statement on a small scheme is usually worth commissioning before the application rather than after the objection.
Collision data and how to get it
Highway authorities hold validated collision records and will normally supply a five year extract for a defined length of road on request, sometimes for a fee. National reported casualty statistics are published by the Department for Transport and give the underlying dataset.
Use the data carefully. An absence of recorded collisions at a quiet access is weak evidence that the access is safe, and inspectors say so. What the data does well is test a specific assertion. If the objection claims a history of accidents at the bend, and five years of records show none involving turning movements, that assertion falls away and the reason for refusal narrows.
Where there is a cluster, look at the causation recorded rather than the count. Loss of control on a wet bend 300 metres away tells you little about a new driveway.
Hedges, verges and land you do not own
Most splay problems are solved by cutting something back, and that is where ownership bites. If the visibility land is highway verge, the highway authority controls it and works will need consent, typically under a section 184 or section 278 agreement under the Highways Act 1980. If it belongs to a neighbour, you cannot deliver the splay and a condition requiring you to do so is unlikely to be lawful unless there are reasonable prospects of it happening.
Serve the right ownership certificate and notice. A Certificate B naming the adjoining owner, with the agricultural holdings position addressed, is part of the evidence that the splay is deliverable.
Hedgerow removal has its own controls. A field boundary hedge may be protected under the Hedgerows Regulations 1997, and a hedge that has to be laid back rather than removed changes the arboricultural and ecological position, sometimes pulling in a tree survey where mature boundary trees stand inside the splay.
Conditions that can overcome the objection
Highway officers are often content to recommend approval with conditions once the geometry is proved. The conditions that do the work are:
- Provision of the splay before first occupation, with a plan reference.
- Retention of the splay clear of obstruction above a stated height in perpetuity.
- Access surfacing and drainage so that water and loose material do not discharge onto the carriageway.
- Closure of any redundant access and reinstatement of the kerb and verge.
Draft them yourself and offer them. An applicant who supplies workable wording gives the officer a route to approval, which is the practical point made in our note on overcoming a highway safety refusal reason.
Taking a highways refusal to appeal
Householder appeals run to the twelve week deadline and use the simplified householder procedure. Other refusals allow six months and are usually written representations for a scheme of this size. The appeal statement needs the survey, the measured splay drawing, dated photographs from the driver's eye position and the collision extract, all referenced in a Planning Statement that puts them against the Framework test rather than against the county standard alone.
Inspectors are used to authorities applying a standard mechanically. What persuades them is measurement. But be honest about an access that is substandard on any reading, because an appeal on a splay that cannot be achieved wastes the fee and hands the authority a second refusal reason.
This is general guidance, not legal advice, and highway standards vary between authorities, so check the position with your local planning authority or a qualified transport professional before relying on it. PlanScope produces AI-assisted drafts of the supporting documents an access case needs, with the site facts it cannot know flagged for you to complete. Enter your postcode to see which reports your site needs.
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Frequently asked questions
What does a 2.4 by 43 metre visibility splay mean?
The first figure is the set-back from the edge of the carriageway to the driver's eye position, and the second is the distance you must be able to see along the road in each direction from that point. The 43 metre figure corresponds to stopping sight distance at around 30mph in Manual for Streets. Both are measured over a range of eye and object heights.
How long does a speed survey need to run?
Seven consecutive days is the normal expectation, using automatic tubes positioned clear of the junction so that turning traffic does not depress the readings. Avoid school holidays, August and December. The output that matters is the 85th percentile wet weather speed in each direction, which is the figure used to set the required sight distance.
Can a condition require a splay on a neighbour's land?
Only where there are reasonable prospects of the work being carried out within the life of the permission, which in practice means an agreement or a strong indication of consent. A condition requiring works on land the applicant cannot control, with no prospect of delivery, is unlikely to be lawful. Resolve the ownership position before you rely on the splay.
Does an absence of recorded collisions prove an access is safe?
No, and inspectors regularly say so. A quiet access with no recorded collisions may simply have carried very little traffic. Collision data is most useful for testing a specific claim in the objection, such as an accident history at a nearby bend, rather than for arguing that the access must be safe because nothing has happened yet.
How long do I have to appeal a highways refusal?
Householder appeals must be lodged within twelve weeks of the decision and use the simplified householder procedure. Other planning appeals allow six months, and a small residential scheme will normally be dealt with by written representations. Check the deadline on the decision notice, because a late appeal cannot be accepted.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.