Northern Ireland is uniquely placed to do this: the entire road network is under the control of a single highway authority - the Roads Service - which is responsible for every road, bridge and street light across the area. It is directly controlled by the Department for Regional Development, which means that decisions can be made at the national level over local streets.
Mr McDevitt has issued a consultation  to gauge interest in his proposals. He suggests that shifting the speed limit to 20mph would have a huge effect on safety and take up of active travel.
Many local authorities in Britain have already adopted 20mph as the standard urban speed limit, including Portsmouth, Oxford, Islington, Hackney. A recent pilot of 500 20mph streets in Bristol  found that cycling and walking increased in the areas with 20mph limits, while residents became more enthusiastic about 20mph over the course of the trial.