Drivers in Canada can be pulled off the road for being too fast or too slow. But what about the sensitive issue of being too old?

Researchers with Candrive, a group that studies the driving habits of older adults, are trying to answer that perennial question with a new, nation-wide study.

The study aims to come up with a dependable method for doctors to figure out how long a senior should be on the road.

Currently, Canada has no national standard for evaluating older drivers who may have poor eyesight and slower reflexes.

While provinces such as Alberta and Ontario require driver re-testing at age 80, doctors in other regions typically decide who is or isn't fit to operate a vehicle.

Though 81-year-old Victor Derksen said he considers himself a safe driver, he admits that not all seniors are.

"I have personally seen people on the road who shouldn't be on the road," he told CTV Winnipeg.

Derksen's cautiousness appears to be paying off. He has 55 crash-free years of driving under his belt.

Seniors are the fastest growing segment of Canada's driving population, according to the Canadian Association of Occupation Therapists. It's been estimated that the number will double by the year 2040.

While the number of elderly drivers in Canada continues to climb, researchers stress the Candrive study isn't about finding a standard re-testing age for seniors.

Researchers say they're trying to come up with a series of tests that can be used by physicians to evaluate elderly drivers.

Study participants, who are all volunteers aged 70 and older, are having their driving and health habits monitored for five years. The study is currently in its second year.

About 1,000 seniors are being followed in Victoria, Winnipeg, Thunder Bay, Ontario, Toronto, Hamilton, Ottawa and Montreal.

With a report from CTV Winnipeg's Jill Macyshon and files from The Canadian Press