The revised road transport bill means the police now have the power to detain a driver for up to 30 minutes if breath or drug testing equipment is not available.

The laws also restrict defence options for drug drivers, remove the requirement for police to arrange a medical examination for alleged drink drivers, and create a new offence of refusing to provide a screening test.

ACT Attorney-General Simon Corbell said the changes improved safety for all road users by strengthening ACT Policing's ability to enforce drug and drink driving laws. .

But the changes have attracted criticism in legal circles, with some lawyers expressing concerns that the changes could erode civil liberties.

Canberra Criminal Lawyers principal Paul Edmonds said it was unreasonable to let police curtail a law abiding person's right to liberty if they were not able to conduct a test on the spot.

Mr Edmonds said an innocent driver could be obstructed from urgent business, such as a traveller running late for a flight or a doctor on urgent medical business.

''[The government line is] that only drivers suspected of being under the influence will be subject to the new requirement to wait for up to half an hour if the police do not have any breath-testing equipment with them, or none in working order,'' Mr Edmonds said.

''But the act actually provides for all drivers to be subject to such a requirement, which is a clear breach of the right to liberty under the Human Rights Act, given most drivers will not be suspected of committing any offence at the time they are stopped for a RBT (random breath test).''

Mr Corbell said police always had a common law right to detain drivers, but the new rules now set a time limit on that delay.

In a media statement issued after the laws passed, Mr Corbell described the 30-minute wait limit as ''reasonable''.

''This government is committed to reducing the number of deaths and serious injuries on our roads,'' Mr Corbell said.

ACT Policing statistics show that impairment was the major factor in almost 40 per cent of all fatal crashes in the ACT.

A driver with a blood alcohol concentration of 0.05 is twice as likely to crash as a driver who has not had a drink.

''An impaired driver represents a threat to themselves, their passengers and to other road users,'' Mr Corbell said.

''Every drink or drug driver we take off the road reduces the risks of death or serious injury to members of our community.''