Public safety zones at the ends of runways

A public safety zone airport constraint is a wedge of land off the end of a runway where the planning policy is, in short, no increase in the number of people present. It exists because the ground immediately beyond a runway threshold carries a measurable risk of an aircraft accident, and the response chosen in this country is to limit occupancy rather than to build differently.

The boundary is drawn from calculated individual risk. A public safety zone covers the area within the one in 100,000 per year individual risk contour, and inside the much smaller one in 10,000 contour the policy goes further: occupied buildings are expected to be cleared rather than merely left alone.

How a zone is defined and who defines it

Public safety zones are set by the Department for Transport, using the traffic and fleet forecast for each airport, and the policy that governs development within them is set out in the department's circular on the control of development in airport public safety zones. They apply at the busier licensed aerodromes rather than at every airfield, so a small general aviation strip will not normally have one.

The shape follows the risk rather than the geometry of the runway. Zones are broadly triangular, extending along the extended runway centreline with the widest part nearest the threshold, and they are updated as traffic forecasts change. A zone can therefore grow, which matters on a long land promotion.

Two things follow from the fact that the boundary is a risk contour. The zone is not a fixed distance you can look up, and a site just outside the line is not risk free, it is simply below the threshold at which the policy bites.

What the policy restricts

The core policy is that there should be no new or replacement development, and no change of use of an existing building, which would increase the number of people living, working or congregating in the zone. Housing, offices, schools, places of assembly and anything that brings people together in numbers all fall foul of it.

The circular identifies categories of development that are normally acceptable because they involve very low occupancy for the area they cover. In broad terms these are uses where people are present briefly or sparsely: open car parking, open storage, some agricultural uses, golf courses and playing fields without stands or clubhouses, and infrastructure such as roads.

Note the pattern. Acceptability turns on the number of people and how long they stay, not on the resilience of the building. Strengthening a structure does not answer the objection, because the risk being managed is to people on the ground rather than to property.

Existing buildings and changes of use

Buildings already in a zone are not required to be demolished, except within the innermost contour where the policy expects clearance, usually achieved by the airport operator offering to purchase the affected properties.

Changes of use are where developers get caught. A warehouse in a zone can continue as a warehouse, but converting it to a gym, a trampoline park, a place of worship or offices increases occupancy and runs directly into the policy. Extensions are assessed the same way: an extension that adds floorspace without adding people may be acceptable, and one that adds workstations is not.

Replacement dwellings are also restricted, which surprises owners. Rebuilding a house that already exists still counts as new development, and the policy does not simply carry over the existing occupancy.

Who is consulted and how much weight the advice carries

The airport operator holds the zone plan and will be consulted on applications within it, and the department's policy is the material consideration the council applies. Unlike the statutory consultee arrangements around hazardous installations, the mechanism here is policy rather than a consultation direction, and councils generally apply it as written because the policy basis is national.

The practical effect is close to a veto for occupied development. A council that grants permission for housing inside a public safety zone has to explain why it departed from national policy on a matter of life safety, and that is a difficult decision to defend on appeal or in a committee report.

So treat an adverse position as a design constraint rather than as an argument to be won. The realistic outcomes are to move the occupied floorspace outside the contour, to change the mix so the part inside the zone carries a low occupancy use, or to accept that part of the site is open land.

How this differs from aerodrome safeguarding

Two separate regimes operate around airports and they are constantly confused.

Safeguarding applies over a much larger area, is triggered by height and by certain types of development, and operates through consultation with the aerodrome operator under the safeguarding direction. A site can be perfectly acceptable for safeguarding purposes, because nothing is tall, and still be undevelopable because it sits in a public safety zone. The reverse is also true.

Wind turbines, tall buildings and even tower cranes engage safeguarding without engaging public safety zones at all, since they are about what happens in the air rather than about who is standing on the ground.

Checking the zone before you commit

There is no single national map layer you can rely on, so ask.

1. Ask the local planning authority whether the site falls within a public safety zone. Many councils show the zones on the local plan policies map or their constraints layer.
2. Ask the airport operator's planning or safeguarding team, giving the site boundary, and ask for the current zone plan rather than an older one.
3. Read the local plan. Authorities near an airport almost always carry a policy on public safety zones, and the policy wording tells you how the authority applies the national position.
4. Check the planning history of adjoining land, because refusals in a zone are explicit about it in the officer report.
5. Build the answer into the option or contract as a condition precedent where the site is anywhere near an extended runway centreline.

Do this before the layout is drawn. A zone that clips the corner of a site can usually be designed around at concept stage, and cannot be designed around after a scheme has been costed on a unit count that includes the affected area.

Constraints like this are the ones that reward early desk work, in the same way as the invisible designations we describe in Archaeological Priority Areas and their tiers, and the capacity limits imposed by protected views and viewing corridors.

Making the application read properly

Where part of a site lies within a zone and the scheme places only acceptable uses there, say so directly in the supporting documents. Include a plan showing the zone boundary as supplied by the airport operator, the extent of the site inside it, and a schedule of what is proposed in that area with an occupancy estimate.

The occupancy estimate is the part that convinces. A car park with a stated number of spaces and no attendant, or a playing field with no stand and no clubhouse, gives the case officer a figure to write into the report. A description that says landscaping does not.

One honest limitation. The contours are recalculated as forecasts change, and a zone plan issued five years ago may not be the current one. Ask for the current plan in writing, note the date on your constraints drawing, and re-check before submission if the promotion has been long. You can see which of the 66 report types a constrained site is likely to need on the PlanScope report index, and you can enter a postcode on PlanScope to start building the constraints picture.

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 confirm the position with the local planning authority and the airport operator before relying on it.