Case for 20mph speed limits being researched
The government has commissioned research into the effects of cutting urban 30mph speed limits to 20mph.
The research is to be led by London University Professor Michael Maher and is expected to take three years.
Transport Minister Robert Goodwill said the research will examine the impact on collisions, casualties and air quality.
In reply to a question from Green MP Caroline Lucas, Mr Goodwill said there were no plans to make 20mph the default speed limit.
In her question, Ms Lucas asked whether ministers had considered making 20mph the "national default speed limit".
In his written reply Mr Goodwill said: "Local authorities are best placed to determine the speed limits for their areas, based on local knowledge and the views of the community, and have the powers to do so."
He added: "The department is about to commission comprehensive research into the effects of 20mph limits.
"This will cover many aspects including effects on speed, collisions, casualties, and modal shift [i.e. whether people switch from cars to other forms of transport].
"The research will also consider air quality, best practice, road users' perceptions and effects on the quality of the environment, as well as relevant research from other countries."
A spokesman told the BBC that the research had now been commissioned.