The federal government’s pledge to legalize marijuana by the spring of 2017 has local police agencies questioning the potential impact the move may have on road safety.

The Calgary Police Service has concerns the legislation could be in place before the force can adopt new testing methods for pot-related impairment.

“Canada has to wait to find out what law has passed in order for us to then research and determine what tools we’re going to be able to use to enforce whatever laws are passed,” said Sgt. Richard Butler of the Calgary Police Service alcohol and drug recognition unit.

South of the border, some states have adopted a zero tolerance policy for drivers while others allow up to five nanograms of tetrahydrocannabinol (THC). “With alcohol, we can say everybody is impaired at a level of 100 milligram per cent,” explained Butler. “The levels haven’t really been established yet for THC.”

While the Canadian standards for marijuana-related impairment have not been determined, police say there are tried and true detection methods for impairment including standardized field tests.

“Signs of impairment are not unique to any one drug.” said Butler. “We’re not just using one tool to determine impairment.”

Saliva tests are being considered for THC detection but some question their reliability.

“They just don’t tell you anything,” said Dr. Mike Lynn, CEO of Hound Labs Inc. and the developer of a THC breathalyzer. “It doesn’t differentiate what you did an hour ago versus five days ago.”

A number of companies have pitched their THC detection devices to the Calgary Police Service. The service will not consider testing any technology until the federal government enacts legislation establishing a threshold of impairment.

Butler says the decriminalization of marijuana will likely result in a greater number of drivers on Calgary’s streets impaired by marijuana use.

“We’re certainly expecting those numbers to increase once the new laws come into effect which allows the legalization of marijuana,” adds Butler. “That’s one of the reasons we’re not looking forward to the new law here.”

According to Butler, marijuana-related impairment is as problematic as alcohol impairment and results in nearly as many crashes and deaths where pot has been legalized.

With files from CTV's Rahim Ladhani