Kerb extensions

Description

Kerb extensions are a localised widening of the footpath at intersections or mid-block, which extend the footpath into and across parking lanes or the road shoulder to the edge of the traffic lane. Kerb extensions are also known as buildouts, outstands or blisters. They reduce the crossing distance for pedestrians. Examples of kerb extensions are shown below.

Retrofit kerb extension, Brightwater. (Photo: Jeanette Ward)

Kerb extensions to support a zebra crossing, Christchurch. (Source: Canterbury maps)

When to use

Check whether a kerb extension is a suitable treatment for your site by referring to:

PNG: Crossing selection process

Kerb extensions should also be considered to support other crossing types to minimise the crossing distance.

Benefits

• Reduces crossing distance and therefore crossing time.
• Improves safety of pedestrians because they are more visible to oncoming drivers and can view approaching traffic better.
• Creates space for pedestrians to wait without blocking others walking past.
• Physically prevents drivers from parking and blocking the crossing point.
• Can help to slow vehicle speeds by narrowing the road.

Implications

• Does not give pedestrians priority so can be less suitable for some pedestrian user groups.
• Can cause issues for cyclists particularly on narrower roads.
• Can create an obstruction that may be struck by cyclists and vehicles.
• Where the kerb alignment is being altered they can create drainage issues and places where rubbish can accumulate (‘stick on’ extensions could overcome this if designed well).

Recommended parameters

• Primary Safe System treatment if operating speeds are below 30km/h. Supporting treatment if operating speeds above 30km/h[1]
• Should be a supporting treatment for other crossing types and aids to reduce the crossing distance.
• Operating speed 50km/h or less.
• Only appropriate on their own for low pedestrian demands and traffic volumes less than about 7500vpd.

The Crossing aids and pedestrian delay section discusses the effect of kerb extensions on pedestrian delay compared with other treatments.

PNG: Crossing aids and pedestrian delay

Kerb extensions on their own are most beneficial on roads with flows less than 500 vehicles per hour. They should also be used to support

• platforms
• zebra crossings
• signalised crossings
• and, where there is sufficient width, pedestrian or median refuges.

Do not use where any part of the kerb extension would protrude into a lane used by moving traffic or leave insufficient space for safe cycling.

Legal considerations

An RCA may provide a kerb extension to guide a pedestrian to a place at which to cross a roadway (TCD Rule, 8.8(4)) and the device must convey a clear and consistent message to road users (TCD Rule, 8.8(5)).

On its own, a kerb extension does not require a driver to stop their vehicle while a pedestrian crosses the roadway (TCD Rule, 8.1(2)).

Land Transport Rule: Traffic Control Devices 2004

Design considerations

Access to the crossing point on the kerb extension should be provided by kerb crossings installed partly or wholly within the kerb extensions. It is important to ensure sufficient width for cyclists past the kerb extension. Landscaping and street furniture must not obscure visibility for pedestrians or drivers, particularly on the upstream side, at any time of the year. A kerb extension can be co-located at a residential driveway to minimise on-street parking loss. Consider whether on-street parking spaces should be marked, and/or no stopping lines included around the kerb extensions to ensure vehicle parking occurs away from the crossing aid.

PNG: Landscaping at crossings

PNG: Street furniture

Design elements

Kerb extensions should comply with the general dimensions in the table and figure below.

Table: Kerb extension design elements

Example of a mid-block kerb extension. (TCD Manual Part 5 Figure 7‑1)

Note the curve radius of the figure above is dimensioned so street sweeper trucks are able to clean the kerb and channel.