A grisly slaying on a Greyhound bus has prompted calls for tighter security on Canadian bus lines, despite the company and Canada's transport agency calling the stabbing death a tragic but isolated incident.

Greyhound spokeswoman Abby Wambaugh said bus travel is the safest mode of transportation, even though bus stations do not have metal detectors and other security measures used at airports.

"Due to the rural nature of our network, airport-type security is not practical. It's a very different type of system," Abby Wambaugh said from Greyhound's corporate offices in Texas.

In a release Friday, Transport Canada said the slaying was a "tragic and unique case in Canadian history," and added it has developed a policy for maintaining security for rail and transit operators.

But the agency also said Greyhound buses don't pose the highest security risk, and that any plan would have to involve all levels of government, law enforcement and industry.

"In general, Transport Canada has adopted risk-based approach to security in all modes," the release said. "This means the risks are evaluated and mitigation measures are put in place.

"On this basis, Greyhound buses do not present the highest risk area."

Metal detectors 'impractical': Motor Coach Canada CEO

But the union that represents Greyhound bus drivers in Canada is calling for passengers to pass through some form of metal detection to protect those on board buses.

"Maybe airport screening is not feasible per se," said Jim Higgs, president of Amalgamated Transit Union Local 1374 in Calgary. "There has to be some method now put in place so we can check for metal."

Some bus passengers, like Bert Hausauer, said they agree with the union that more needs to be done.

"There should probably be some enhancements in the security for sure, making sure people aren't getting on with weapons and stuff," he said.

Brian Crow, president and CEO of Motor Coach Canada, said bus companies across the country will definitely examine their security and training policies in the wake of the slaying.

But Crow called demands for metal detectors at bus stations "rather impractical," as the vast majority of passengers are more likely to board buses at gas stations, convenience stores and other roadside stops than central terminals.

"The security at the bus terminal is important, but that would only reach a few of our passengers," he said, noting that Wednesday's attack could just as easily have occurred at a movie theatre or a sporting event.

"Metal detectors aren't going to give us that assurance that incidents like this, while very, very rare, won't ever happen again."

With files from the Canadian Press