It's the key principle of a police checkstop: the locations are kept under wraps, so drunk drivers can't easily avoid them. But in a social-media era, that's not always the case.
Police officers across Canada continue to grapple with Twitter users revealing the location of impaired driving checkstops, which ramp up during the holiday season. An Edmonton bar was under fire for revealing one such location, and last week, Alberta's Minister of Justice and Solicitor-General Jonathan Denis took to Twitter himself to berate the user behind an account dedicated entirely to revealing locations of Calgary checkstops.
"What you're doing could potentially result in injury or death of innocent people," he wrote the anonymous user, who fired back, saying the account is meant to empower drivers who may be on the cusp of the legal limit.
But Mr. Denis doesn't buy it.
"It's not illegal to do it. I'll tell you that it is wrong. The checkstops are there for a reason, and that is to protect every one of us," he said in an interview.
It was Edmonton's Treasury Vodka Bar that revealed a checkstop location one night this month. Management later deleted the tweet, blamed an ex-employee and responded by advertising $20 cab-ride vouchers to customers during the rest of December. "We do not condone drinking and driving in any way," the bar said in a statement.
Calgary police said it's "frustrating" that people undermine their efforts by revealing checkstop locations. It's different than information about speed traps, which are often shared on Twitter and on radio stations, police say.
"And we have no problem with that as it has the desired effect of slowing drivers down," Calgary Police spokesman Michael Nunn said in an e-mail, adding: "When people tweet locations they are giving impaired drivers the option to avoid detection and potentially put themselves and other public in danger."
Some departments move checkstops around, to render such tweets obsolete, but lose valuable time in doing so – and all because of messages from accounts with a relatively small following (such as the Calgary account, with 2,000 followers). Altruistic Twitter users have urged others to broadcast fake checkstop locations to muddy the waters of those revealing actual checkstops.
But there's nothing legislators can do – Mr. Denis says Alberta has tried – as any law would inevitably bump up against a person's right to freedom of expression. "I don't think there's anything we can do legally about this," the minister said.
Others agencies say it's a new twist on an old problem.
"At this point, we're looking at it basically as an updated version of people flashing their lights," said Constable Tammy Lobb, a spokeswoman for the Halifax District RCMP, which arrested four drivers and suspended six others in checkstops on Saturday.
Mothers Against Drunk Driving chief executive officer Andrew Murie said publicizing a checkstop location is "appalling," but regrettably widespread.
"The one I really worry about is more people saying, 'Well, if I know where all the sobriety checkpoints are, because people are tweeting them out, then I can go out and drink and I don't have to worry about getting pulled over by police,' " he said.
Most police agencies across Canada frown upon the practice, although the Saskatoon Police Service, for example, has said it's not a big deal. "There is no point in ignoring the fact that people are going to spread the word amongst their friends," spokeswoman Alyson Edwards told the CBC last year.
Mr. Murie praised those who "flush people out" when they reveal checkstop locations, and said police have adapted. "The police are being clever about it, but we shouldn't have to."