Council highway standards: access widths and visibility splays

A new access for one or two houses is refused far more often on visibility than on anything else. The highway authority asks two questions: can a driver leaving your access see far enough along the road in both directions, and can that visibility be kept clear permanently? If the answer to either is no, the objection is usually fatal, because unlike a design point it cannot be conditioned away.

The good news is that the standards are published, the geometry is drawable, and most of the work can be done before you buy the land.

Who sets highway standards in your area

The local highway authority is the county council in two-tier areas and the unitary or borough council elsewhere. In London it is the borough for most roads and Transport for London for the strategic network. Where an access is proposed onto a trunk road or motorway, National Highways is the authority and the standards are considerably more demanding.

Highway authorities publish design guidance under various names: a highway design guide, residential design guide, streets design manual or highways development management standards. Find yours and use its figures rather than a national default, because the local document is what the consultee will apply.

The planning application is only half the process. Physically forming or altering a vehicle crossing over a footway or verge needs consent under section 184 of the Highways Act 1980, and works within the highway to build a bellmouth or a footway usually need an agreement under section 278. Both are separate applications with their own fees and timescales, and planning permission does not authorise either.

Visibility splays and design speed

A visibility splay is a triangle at the access, kept clear of anything that would obstruct a driver's view. It has two dimensions.

The X distance is the set-back into the site, measured from the edge of the carriageway to the driver's eye position. The commonly applied figure is 2.4 metres, reduced to 2 metres in low-speed situations where the authority accepts it.

The Y distance runs along the carriageway in each direction and is derived from stopping sight distance for the design speed of the road. Design speed is not the speed limit. It is based on measured vehicle speeds, usually the 85th percentile wet weather speed, taken from a speed survey. On a road signed at 30 miles per hour where traffic actually runs at 38, the Y distance required will reflect the higher figure.

Two details decide many cases.

Visibility is measured between a driver's eye height of 1.05 metres and an object height of 0.6 metres, which is why a 900 millimetre boundary wall inside the splay is an obstruction and a flush verge is not.

And the land within the splay must be within your control or within the highway. A splay drawn across a neighbour's front garden is worthless unless you own it or have an enforceable right over it. Where the splay crosses third-party land, the highway authority will object, and the answer is either a legal agreement or a redesigned access.

Vegetation counts too. Hedges, shrubs and low branches inside the splay must be maintained below 600 millimetres, which becomes a condition. Where a protected tree sits within the splay, you need consent for the works, and our note on checking and applying for works to protected trees sets out that process.

Access width, gradient and gates

Local standards vary, so treat the following as the shape of the requirement rather than the numbers for your area.

• Width. A single dwelling access is commonly required at around 3 metres minimum, with wider dimensions where the drive serves several houses or where two vehicles must pass. Many authorities specify a wider throat at the highway edge, tapering back into the site.
• Gradient. A common standard requires the first several metres from the highway boundary to be near level, often no steeper than 1 in 20, with steeper gradients permitted further into the site. The purpose is to keep a stationary vehicle level while the driver looks both ways, and to stop surface water running onto the footway.
• Gates. Where gates are proposed, they are normally required to open inwards and to be set back far enough from the highway boundary for a vehicle to stand clear of the carriageway while they are opened. Five to six metres is a frequent requirement.
• Surfacing. The first few metres are usually required to be bound rather than loose, so that gravel is not dragged onto the highway.
• Drainage. Surface water must not discharge onto the highway, which normally means a channel or a gully at the boundary.

Draw all of these on the site plan and dimension them. A highways officer reviewing thirty applications a week will approve a drawing that answers the questions and will object to one that requires measuring.

Turning and manoeuvring for a new dwelling

Where the access is onto a road that is not a quiet residential street, the authority will want vehicles to enter and leave in forward gear. That means a turning area within the site, sized to the vehicle expected, which for a house is normally a car and a refuse vehicle only if the bins are collected from within the site.

Show it with vehicle tracking rather than by eye. A turning head that looks adequate on a plan often fails when the swept path of a standard car is drawn on it, particularly where a planting bed or a bin store sits in the corner.

Bin collection is worth resolving early. Most authorities will not send a refuse vehicle down a private drive, so the design needs a collection point within a stated dragging distance of the adopted highway, on a hardstanding, and that point has to appear on the drawings.

Where Manual for Streets applies and where it does not

Manual for Streets, and its companion for larger and busier streets, is the design guidance for residential streets and lightly trafficked roads. It replaced older, more rigid standards and it allows visibility and geometry to be derived from observed conditions rather than applied mechanically.

The Design Manual for Roads and Bridges applies to trunk roads and motorways, and its standards are stricter. Some highway authorities apply parts of it to their own higher-speed rural roads, which is a source of argument, because a rural lane with a 60 miles per hour limit is often being used at far lower speeds.

Where you think the authority is applying the wrong document, the way to make the point is with a speed survey carried out to a recognised method over a full week, not with an assertion about how fast traffic seems to go. Surveys are inexpensive relative to the cost of a refused access, and a measured 85th percentile speed changes the required Y distance immediately.

What to submit so highways respond first time

For a single dwelling or a small scheme, this set answers almost every question a highways consultee asks.

1. A site plan at 1:200 or 1:500 showing the access, the splays with X and Y dimensioned, and the ownership boundary.
2. A long section through the access showing the gradient over the first ten metres.
3. A speed survey where the required Y distance is contested, with the method and dates stated.
4. Vehicle tracking for entry, turning and egress in forward gear.
5. Photographs along the road in both directions from the driver's eye position.
6. A short Transport Statement where the scheme is more than one or two dwellings, covering trip generation, parking and servicing.
7. A Construction Traffic Management Plan where the site is constrained, which is often conditioned but is quicker to submit up front.

Get the access right at the outset. It is the one element of a small scheme where a late change usually moves the house, the drive and the drainage all at once.

Enter your postcode on PlanScope to see which reports your site is likely to need. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. This is general guidance rather than legal advice, so check the position with your local planning authority or a qualified professional before relying on it.