What’s the purpose of traffic calming measures?

By Alicia Jarvis
Updated on July 30, 2021


What’s the purpose of road humps, chicanes and narrowings? 

To reduce traffic speed – In congested locations with walkers and children, traffic-calming measures help to keep vehicle speeds low. A pedestrian is significantly more likely to survive a collision with a car travelling at 20 mph than a pedestrian is to survive a collision with a vehicle travelling at 40 mph.


Psychological traffic calming 

Shared spaces are areas where road furniture, such as kerbs, traffic lights, signs, white lines, and other road markers, have been removed to produce ‘naked roadways.’

According to the hypothesis, eliminating the sense of security offered by road furniture induces the driver to be more cautious. This plan is currently being reviewed, and the Department of Transport has recommended local governments to halt the expansion of shared space schemes.


Road humps 

If road humps or cushions are put outside of 20 mph (32 km/h) zones, there will usually be warning signs at the start of the section of road where the hump or sequence of humps is installed. Triangle and edge line-markings at each hump will likely be installed too.

These can be humps with a round or flat top that are set across the carriageway. They are used on roads with a speed restriction of 30 mph (48 km/h) or less.

In certain places, the humps take the form of ‘cushions,’ which cover only a portion of the lane and are meant to allow heavier vehicles, particularly buses, to straddle them.


Road narrowings

Roads can be narrowed by constructing ‘build-outs’ on one or both sides.

As you approach the narrowing, don’t speed up, but be prepared to slow down or yield to approaching vehicles. Hold back and give bicycles and motorcyclists room to pass; don’t try to pass at the same moment.

If these are installed outside of 20 mph (32 km/h) zones, warning signs identifying which side of the road the narrowing occurs are usually provided. Give way road markers on one side of the road, together with signage indicating priority for oncoming vehicles are usually present.

If these are on your side of the road, you must always yield to traffic coming from the opposite direction. If no priority is provided in either way, all drivers must guarantee that they can pass through the narrowing without harming vehicles arriving from the opposite direction.