Kerb ramp design

Kerb ramps are where a localised area of the footpath is lowered to the same level as the adjacent roadway. Kerb ramps are also known as ‘kerb cut-downs’, ‘pram crossings’, 'drop kerbs' and 'dropped kerbs'.

If the kerb ramp is too steep, or there is too much of a lip between the traffic lane and the channel, I can't use it and have to go find another one. It can mean a much longer walking trip for me. Wendy

Kerb ramps are an integral part of most crossings. The alternative is a blended kerb where the footpath and roadway meet at the same level which are usually found at pedestrian platforms, raised zebra crossings, kerbless streets or shared spaces.

Design considerations

When designing kerb ramps, it is important to ensure that:

• if there is a kerb ramp on one side of the roadway, there is also one on the other to prevent pedestrians being ‘stranded’ on the roadway itself (for example a wheeled pedestrian)
• there are no low points where the ramp meets the road surface where water can collect
• if installed at a pedestrian crossing point, the whole kerb ramp is contained within the crossing pavement markings
• a shallow gradient is preferred.

Every kerb ramp comprises:

• the ramp, which is the area pedestrians cross to change their grade
• the landing, which is where pedestrians move between the ramp and the footpath
• the approach, which is the section of footpath next to the top landing
• the gutter, which is the drainage trough at the roadway edge.

Perpendicular kerb ramp

The general form of a kerb ramp is illustrated below.

Typical perpendicular kerb ramp.

Parallel and combination ramps

The use of parallel and combination ramps may be appropriate when the path is also used by cyclists or high volumes of people using wheeled mobility devices however they are generally less comfortable for pedestrians as they require people on the through route to change levels.

Parallel kerb ramp.

Combination kerb ramp.

Horizontal geometric design for mobility scooters technical note

The Horizontal geometric design for mobility scooters technical note provides guidance on the radius or chamfer required to accommodate the turning envelope of a mobility scooter travelling between a kerb ramp and path.

Waka Kotahi technical advice note #21-06: Horizontal geometric design for mobility scooters

Design elements

Pedestrians, especially those with mobility impairments, pushing a heavy buggy or wheelchair, or carrying luggage are likely to experience difficulty in negotiating steep kerb ramps (gradients of 1:8) noting these gradients are relative to the horizontal and not the surrounding surface. In hillside areas it may not be possible to achieve these requirements, however due consideration needs to be given to the accessibility needs of all pedestrians. Many people pushing small wheels find it difficult to change direction while on the ramp. This means curved kerbs require kerb ramps with bottom landings as seen in the illustration below. 

Correct bottom landing arrangement.

Kerb ramps can be problematic for some people with impaired vision because they often use the kerb face as a tactile cue for the footpath edge and kerb ramps can increase the risk of inadvertently walking out into the roadway. To avoid this, all kerb ramps should incorporate appropriate tactile indicators. Warning tactile indicators should be arranged so that it is not possible to inadvertently bypass them and enter the roadway.

Warning tactile indicators shall be installed a minimum of 600mm deep and the full width of the kerb ramp, but need not cover the entire face of the kerb ramp.

Where it is desirable for users who are blind or have low vision, to detect that they are entering the kerb ramp from the side, flares with an abrupt change of grade steeper than 12.5% but no steeper than 17% are appropriate. This will be particularly appropriate where users entering from this direction could inadvertently enter the roadway by bypassing the warning tactile indicators. In most situations it will be desirable for the entry across the flare at the top of the ramp to be more gentle than near the kerb.

The figure below shows a typical kerb ramp design.

Typical kerb ramp design.

Table: Design elements of kerb ramps

Kerb ramps should comply with the general dimensions outlined in the table below.

Element	Key issues	Additional information
Ramp	Desired gradient is 5% where there is space. Normal maximum gradient 8% Maximum gradient 12%	A gradient of 10% should only be considered for constrained situations where the vertical rise is less than 150mm. A gradient of 12% should only be considered for constrained situations where the vertical rise is less than 75mm. Slopes more than 12% are very difficult for people pushing small wheels to negotiate. To avoid using these steeper gradients, lower the footpath as shown in the parallel ramp diagram
	Maximum crossfall 2%	Should be consistent across the whole ramp – avoid twist.
	Minimum width of 1.5m	Wider ramps may be necessary for higher pedestrian volumes.
	Maximum width: equal to the width of the approaching footpath	Wider ramps are difficult for people with vision impairment to detect.
Gutter	Maximum gradient 5%	Anything greater can cause some people to lose their balance at the transition.
	Transition between gutter and ramp	Should be smooth with no vertical face. Ensure that this does not inadvertently happen when the roadway has been resurfaced.   Typical gutter design
Landing	Maximum gradient 2%	To prevent people pushing small wheels overbalancing, or accidentally rolling, and to provide a rest area.
	Maximum crossfall 2%
	Width: equal to that of the ramp
	Minimum depth 1.2m (top landing)	A depth of 1.5m is preferred.
Flare	Maximum gradient 16%	Use the steeper value if a vision impaired person could inadvertently enter and leave the kerb ramp from the side and bypass the tactile indicators.
	Maximum gradient: as per the ramp section	Use these gentler values if mobility impaired people are expected to enter and leave the kerb ramp from the side due to the top platform being too small. For a kerb ramp perpendicular to a straight kerb this results in a splay angle of 45o.
Tactile indicators	All kerb ramps should incorporate appropriate tactile ground surface indicators.	Warning indicators shall be provided on all kerb ramps. Directional indicators are likely to be required unless the crossing point is on the continuous accessible path of travel. For installation requirements, refer to: PNG: Designing for blind and low vision people