If a cyclist or a pedestrian is hit by a motor vehicle at 60kph the death rate is 90%. If they are hit at 30kph the death rate is 10%.
The death rate curve climbs steeply from 30kph so that in most Australian cities and towns where the urban street speed limit is typically 50kph many pedestrians and cyclists die needlessly each year.
For those that survive, injuries are also more serious as the impact speed increases.
The reason for this is simply due to a law of physics: F=ma or force equals mass times acceleration. The greater the speed, the greater the sudden acceleration of the victim’s body upon impact and therefore the greater the force.
This is why cycling advocates across the world including in Australia have been campaigning for years to have speed limits lowered to 30kph on any street with potentially high pedestrian and cyclist activity.
Although there has been little progress in Australia, in Western Europe 30kph is now the standard limit with 50kph the exception.
In the USA progress has been similar to Australia with only some cities in certain cases adopting 20mph (32kph). However New York City has widely implemented 20mph zones and is progressively re-engineering streets accordingly. Washington DC has also just announced a new 20mph limit for local neighbourhood streets.
Now Dublin, Ireland has become the latest city to adopt a city wide 30kph limit with the exclusion of major arterial roads.
Plans to cut speed limits to 30kph on residential streets throughout Dublin were approved in December 2016.
The lower limits will be introduced on a step-by-step basis from March 2017 and will apply on almost all roads in Dublin and its surrounding suburbs.
The council’s head of traffic and transport Dick Brady said the overriding principle in relation to a 30km/h default speed limit was road safety. “It’s in the interest of road safety we would be recommending these new speed limits. We are talking about setting speed limits adjacent to residential areas and school in order to try to ensure the safety of residents and children.”
Motoring groups opposed the plans, as is the case in Australia, although data shows that actual point to point travel time is only slightly increased, due to the length of time motorists already spend stopped or slowing for traffic lights etc.
Part of this story was first published by the European Transport Safety Council