Police in Wiltshire have been given new powers to carry out roadside tests on drivers they suspect have been taking drugs.

Previously there was no legal requirement for drivers to take part in impairment tests. Now a refusal is an offence, the same as refusing to provide a breath test.

Inspector Wayne Smith, head of Swindon traffic police, said: "People who use drugs be it prescribed or illegal, and drive, put both themselves and others at risk of being killed or seriously injured.

"In the past 12 months I am aware of at least two fatal collisions where the drivers were under the influence of drugs. One illegal substances, one prescribed drugs. In both cases this affected the abilities of the drivers. In both cases the driver died."

The tests, to be done by specially trained officers, are designed to show whether a drivers' balance, judgement and ability to do two things at once have been affected by drugs.

A number of officers in Wiltshire have been trained in anticipation of the change in law and more will be trained in the New Year.

Specific detection equipment is also being developed and will be ready next year.

This will indicate the presence of drugs in the same way that a breathalyser indicates the presence of alcohol.