Gardaí will be able to conduct roadside tests on motorists suspected of being under the influence of cocaine, cannabis and heroin under legislation introduced in the Dáil.

Minister for Transport Shane Ross said it was time to do strengthen the law on drug driving in a manner similar to current drink driving legislation.

Exceptions will be made for a “small proportion of multiple sclerosis patients” likely to be prescribed a recently legally licensed form of cannabis, a medication called Sativex, he said.

Introducing the Road Traffic Bill, previously passed by the Seanad, the Minister said the legislation would also allow local authorities introduce speed limits of 20 km/h.

The lower speed limit would not be mandatory as the Jake’s Legacy campaign had advocated in the wake of the death of Jake Brennan (6) in a road traffic incident on the Kilkenny housing estate where he lived.

Mr Ross said the 20km/h limit would not be appropriate to all housing estates and would be difficult to enforce but would be suitable in densely inhabited areas where children might be playing.

The Bill will also give effect to an agreement between Ireland and the UK on mutual recognition of driver disqualification.

And the legislation will introduce a provision for a “third payment option” for fixed charge notices. It will offer a third chance to people to pay fines before having to appear in court.

Motorists who have failed to pay a fixed penalty notice within 28 days, or to pay a higher charge after a further four weeks will receive a third payment notice along with a court summons, allowing court proceedings to be dropped if they pay not more than seven days before the scheduled hearing.

Mr Ross said it would “put an end to cases of people turning up in court and claiming they never received a fixed charge notice”.

Stressing the need for strong drug-driving legislation, Mr Ross said the latest available report of the Medical Bureau of Road Safety showed 58 per cent of the 1,158 specimens tested for drugs were positive for at least one drug and 53 per cent tested positive for two or more drugs.

“What kind of person gets behind the wheel in that state? As we cannot trust such persons to act responsibly, we must act to give An Garda Síochána the tools to protect us from them and them from themselves.”

The Minister said the Bill focused on cannabis, cocaine and heroin, the most prevalent illicit drugs found in specimens. The levels proposed for each of these drugs were chosen based on scientific advice and the experience in other jurisdictions, Mr Ross said.

Fianna Fáil transport spokesman Robert Troy, whose party fully supported the legislation, said it was a “weakness” in the Bill that it ignored the misuse of legally prescribed drugs because there were many people misusing such drugs.

“Sedatives that are used for the treatment of anxiety disorder and insomnia have become increasingly common as recreational drugs, unfortunately.”

Sinn Féin transport spokeswoman Imelda Munster welcomed the introduction of drug driving offences for motorists and lower speed limits but said it had to be backed up with sufficient resources.

“Otherwise it’s not worth the paper it’s written on,” she said.

Ms Munster also said the optional 20km/h speed limit did not go far enough. “We have to ensure that local authorities are properly resourced to ensure all types of traffic calming measures are provided for in housing estates and residential area,” she said.

Debate on the Bill continues.