The ACT government says the revamped roadside alcohol and drug testing regime will improve road safety for all road users in the ACT.

But some lawyers are concerned the new rules could erode civil liberties and could cause unnecessary delays for people on urgent business, such as surgeons on their way to hospitals.

The new laws, due to be debated in the ACT Legislative Assembly next week, will give the police the power to detain a driver for up to 30 minutes if breathalyser or drug testing equipment is not available.

The law applies to all motorists, even if they are not suspected of drinking. The amended road-transport bill will have other changes: restricting defence of honest and reasonable mistake; removing the requirement for police to arrange a medical examination; and it will create an offence of refusing to undertake a screening test for alcohol or drugs.

Police currently have the power to conduct roadside alcohol or drug tests either as part of random breath testing, where a driver is involved in an accident, following a routine traffic stop, or where the vehicle was stopped for another purpose.

But officers have no legislative power to require that a driver remain for a test if a screening device is not immediately available at the scene, or a device is not working. Not all police vehicles are equipped with breathalyser equipment, and only the Belconnen-based Road Safety Operation Team currently carries drug-screening test kits.

ACT Attorney-General Simon Corbell said the change would provide certainty on police powers to temporarily detain a driver to undertake an alcohol or drug screening test.

Mr Corbell said 30 minutes would be the maximum time a person could be detained, but in reality the delay would be shorter.

"The 30 minutes maximum detention period was chosen as an appropriate compromise between the rights of drivers not to be detained for longer than necessary to ensure that the road transport legislation is being complied with, with the time needed to source a replacement screening device," Mr Corbell said.

"Thirty minutes will allow a drug screening device to be sourced from the Traffic Operations Centre in Belconnen … and delivered to any part of metropolitan Canberra where the driver has been directed to remain."

The Attorney-General said similar regimes currently operate in Victoria and Tasmania. "The amendment currently before the Assembly makes no change to the existing grounds upon which the police can require a person to undertake a screening test, i.e. the situation will remain that police do not need reasonable suspicion about the driver being under the influence of alcohol or drugs," Mr Corbell said.

But Paul Edmonds, a defence lawyer from Canberra Criminal Lawyers, said the statutory basis which allowed authorities to randomly stop drivers for a breath test was based on the police being in a position to administer the breath test there and then.

Mr Edmonds, who is a member of the ACT Law Society criminal law committee, said motorists accepted the personal inconvenience of being tested for the greater good of detecting drunk drivers.

But he said the amendment eroded the right to liberty recognised by the Human Rights Act. "This is not simply a matter of personal inconvenience, but rather the power of police to curtail a law abiding individual's right to liberty," Mr Edmonds said.

"It is an unreasonable inroad into the right to liberty to allow the police not only to require a driver who has not committed any offence, and who is not reasonably suspected at that point of having committed any offence, to not only submit to an 'on-the-spot' breath test, but to also make them wait at the roadside for up to 30 minutes just because the police do not have a breath-testing device available or in working order.

"It will be interesting to see what happens if a surgeon on the way to hospital is stopped by police and told to wait for half an hour, or someone running late for a flight."

Mr Edmonds said the laws should have only empowered the police to detain those drivers suspected of driving under the influence for the 30-minute period.