Crossfall – quick reference guide

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Crossfall:

Acute angle made of two straight lines, with thick red line on top labelled "surface" and horizontal lower line. Angle between two lines is labelled "angle".

  • Also called cross gradient, transverse gradient, camber, etc.
  • For utility, we recommend “crossfall” is used to describe the steepest lateral gradient on a path or surface section.

Camber:

Graphic has horizontal lower line. On top, a straight thick red line rises from the left and meets a convex curved line rising from the right. The thick red line is labelled "surface". The apex where the curved and straight lines meet is labelled "crown". The straight line is labelled "straight camber". The curved line is labelled "parabolic camber". The angle between the straight line and the horizontal and the angle between the theoretical average straight gradient of the curved line are both labelled "angle".

  • “Camber refers to the whole road/path cross-section profile, including shape and angle.
  • Also used to describe angle from vertical that wheels are mounted.

Why does crossfall matter?

Can cause mobility aids to tip & people to fall, especially when turning:

A man on a 3-wheeled mobility scooter traversing a surface which slopes down to the left. Arrows show him turning to our right, and tipping over to our left.

Can cause mobility aids, pushchairs & scooters to roll into carriageways:

A woman pushing a double buggy and a child on a 3-wheeled kick scooter are struggling to resist the slope into a road on a steeply cambered pavement. A car is driving down the road to the right of the image.

Increases effort to move, risks muscle & joint injury:

A man using a manual wheelchair is self-propelling across a slope which fall steeply down to the left. Labels show him pushing forwards with his left arm, and pulling back with his right arm to resist turning down the slope.

Common problem locations for unsafe &/or inaccessible crossfall:

Driveways/vehicle crossovers & dropped kerb crossings:

A person using a rollator and a person using a mobility scooter are struggling to negotiate a pavement which has steep crossfalls resulting from badly-made driveway crossovers, combined with wheelie bins left on the flattest bits of the pavement.

Solution: Ensure designs retain 1.5m width safe, level footway at all times.

On-carriageway cycle lanes:

Two people on a side-by-side tandem are squashed onto a narrow, wand-protected cycle lane with steep, curved crossfall into the gutter to the left. A car is driving close by on their right.

Solution: Check crossfalls during surveys, alter gradients and drainage as required.

Chicanes & access restrictions:

A person using a manual wheelchair with clip-on powered attachment is turning sharply while traversing a steep slope in order to pass down a hill through chicane barriers.

Solution: Remove access restrictions, use 1.5m min spaced bollards if required.

1:100 – 1:50 (1-2%) max crossfall is essential for public realm walking/wheeling & cycling accessibility.

References

BS8300-1,

Inclusive Mobility (2021),

Building Regulations Approved Document M

A graphic version of this quick guide is available here

For further details on accessibility and gradients, see our gradients quick guide.

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