I never know how much is safe to drink if I’m going to be driving, how long to wait before driving or whether I should be drinking at all if I’ll be driving. What are the rules? Is one drink still okay? – Emma, Ottawa
If you plan on drinking or using cannabis, plan ahead so you don’t have to drive, safety experts said.
“You don’t want to be out with your friends sitting there trying to do math in your head after you’ve been drinking to figure out if you’re good to drive,” said Robyn Robertson, chief executive officer of the Traffic Injury Research Foundation (TIRF), an Ottawa-based non-profit. “I think the reality is, if you have to ask yourself if you’re okay to drive, the answer is no.”
The Criminal Code of Canada defines impaired driving as having a blood alcohol concentration at or above .08, which is 80 milligrams of alcohol for every 100 millilitres of blood.
But every province and territory except Quebec and Yukon has administrative laws that allow police to suspend your licence on the spot if your BAC is more than .05 (.04 in Saskatchewan and .06 in Nunavut).
While there are online charts and apps that can roughly estimate how high your blood alcohol level might be after a certain number of standard drinks, they’re not accurate for everyone, Robertson said.
“We know there are biological factors that influence how alcohol impairs you,” she said. “It depends on how often you drink, what you’re drinking … whether or not you’ve slept, how much you’ve eaten, whether you are taking cold medication. ... And then men metabolize alcohol faster than women.”
There is also the difficulty of knowing whether your drinks are of a standard size. A standard beer, for instance, is considered to be 12 ounces, but a standard pint contains 20. A standard glass of wine is five ounces but many wine glasses hold considerably more than that. And a standard serving of spirits is 1.5 ounces, but who knows how accurately your host is pouring?
It’s even harder to predict how long your driving will be impaired by consuming cannabis, said Steve Sullivan, chief executive officer of Mothers Against Drunk Driving (MADD) Canada.
“If you smoke a joint, the impact is immediate and then it feels like it wears off really quickly – but you might still have the signs of impairment,” Sullivan said. “And edibles take even longer [to wear off].”
Since THC (tetrahydrocannabinol), the molecule in cannabis that causes intoxication, affects individuals differently, experts say it’s difficult to predict how long you’ll be impaired.
You could face impaired driving charges if you’re tested by police and shown to have more than two nanograms of THC in your blood.
Generally, experts say you shouldn’t drive for at least four to six hours after consuming any amount of cannabis – but the best advice is to just avoid driving entirely, Sullivan said.
Perhaps not surprisingly, consuming alcohol and cannabis together is more impairing than having both separately.
“We know that combined they’re even more risky,” Robertson said.
Sober second thoughts?
Because it’s tough to tell whether you’re impaired while you’re impaired, it’s a good idea to plan in advance for some other way home – whether it’s a taxi, ride-sharing service or a designated driver – or have somewhere to stay until you’re safe to drive, TIRF’s Robertson said.
“As we’re trying to figure out if we’re okay to drive, the question we really should be asking ourselves is: ‘Am I okay with hurting or injuring someone else because I need my car tomorrow, or because I don’t want to pay for a cab, or because I’d feel better sleeping in my own bed?’” Robertson said.
In TIRF’s 2023 survey of drivers, almost 6 per cent of those surveyed admitted driving when they thought they were over the legal limit during the past year.
That’s down from during the first three years of the pandemic, when the number rose every year. In 2022, 10.5 per cent reported driving when they were likely over the limit. In 2021, it was nearly 10 per cent and it was 7.5 per cent in 2020.
“Last year was the highest it has ever been,” Robertson said, adding that it’s not clear why people self-reported driving impaired more often. “There could have been a perception that enforcement wasn’t out there while we’re going through lockdown periods.”
So did more drinking and driving last year mean more crashes and deaths? We won’t know for a while – 2021 is the most recent year with national impaired-related crash statistics, Robertson said.
That year, 391 Canadians were killed in road crashes involving a drinking driver, down from 433 in 2020 and 400 in 2019. Generally, the numbers have been hovering on either side of 400 for the past decade or so after years of substantial declines – from 875 in 1996 to 562 in 2012.
“There have been reductions, certainly from the ‘80s and ‘90s – I think [now] there has been a bit of a plateau,” Sullivan said. “We certainly don’t want to leave anyone with the feeling that alcohol-impaired driving is a problem that’s been solved.”
In surveys, most people who say they drink and drive do it because they think they won’t get caught, Sullivan said.
”Their biggest concern is seeing a police officer; it’s not about getting into a crash and hurting or killing somebody,” he said. “They’re asking themselves: ‘Can I get home without seeing those red lights?’”
Sullivan thinks there needs to be high-visibility enforcement, including alcohol testing any time someone is pulled over for any traffic stop.
Canada’s impaired-driving law changed in 2018 to allow mandatory alcohol screening, which lets police demand a breath sample during any traffic stop – without needing a reasonable suspicion that the driver may be impaired. But Sullivan said police haven’t significantly increased testing, despite the new rules.
“We know from other countries that to be really effective and change people’s behaviour, police need to test about one-third of licensed drivers every year,” Sullivan said. “So every lawful stop – if you were speeding, if you came to a rolling stop at a stop sign, if you have a broken tail light – we would like to see police demand a sample.”
Sullivan said the goal isn’t more arrests and more charges – it’s to keep people from ever driving drunk or high.
“It’s really about changing people’s behaviour,” he said.
Have a driving question? Send it to globedrive@globeandmail.com and put ‘Driving Concerns’ in your subject line. Emails without the correct subject line may not be answered. Canada’s a big place, so let us know where you are so we can find the answer for your city and province.