Measure the
clear opening.
Enter the usable width between solid boundaries. This provides a conservative starting estimate; we confirm the actual number and position from your driveway photo.
The calculation uses a maximum 1,200mm clear gap as a positioning benchmark. It is not structural engineering advice and does not imply Manual 100 is NPSA-certified or impact rated.
Why the final position needs a photo
Driveway width is only one factor. Walls, gates, pavements, drainage channels, turning angles and routes across a front garden can all affect placement. Send one clear photo facing the road and we will check the realistic exit route before agreeing the package.
Where the 1,200mm figure comes from
The UK National Protective Security Authority uses a maximum clear distance of 1,200mm between structural elements as a public-realm vehicle-security design benchmark. We use it only as a conservative spacing guide for this calculator—not as a certification claim. Read the NPSA guide ↗