OTTAWA — It’s the annual crunch time at tire shops and garages throughout the province of Quebec. Drivers must fit passenger vehicles with four winter tires by Dec. 15 and keep them on until March 15, or risk fines of 200 to 300 Canadian dollars.

Despite the threat of financial penalties, the tire law enjoys considerable popular support in Quebec, largely because its potential penalties would affect so few drivers. Before the law was enacted in 2008, 90 percent of motorists already used winter tires. An analysis of accident data over the law’s first two winters, however, suggests that the measure nevertheless contributed to reduced accident rates across the province.

The study (PDF, in French only) by the Quebec Ministry of Transport concludes that all winter accidents fell by 17 percent compared with the five winters preceding the enactment of the law, while accidents causing deaths or serious injuries fell by 36 percent. In Montreal, which held the lowest rate of winter tire use before the law was enacted, serious accidents fell by 46 percent.

The report’s authors noted that since the tire law came into being, road accidents in all four seasons had declined for a variety of reasons. But even after controlling for the factors that improved year-round road safety, the ministry attributed a net accident reduction of 5 percent to the winter-tire law.

The results did not surprise the Transport Ministry.

“We noticed before that the 10 percent of motorists using all-season tires were implicated in 33 percent of accidents in winter,” said Caroline Larose, a Montreal-based spokeswoman for the ministry. At temperatures below roughly 45 degrees, the rubber compounds in all-season tires harden, reducing both traction and tire handling, whereas the winter tires remain supple. The study attributed the reduction of the accident rate to the better handling characteristics afforded by winter tires, even on dry roads.

Ms. Larose said that several other Canadian provinces have contacted Quebec about the efficacy of the tire law, but no inquiries have come from state or federal government agencies in the United States.

The specialized tires are mandatory for all passenger cars and taxis registered in the province, as well as rental cars picked up from locations in Quebec, irrespective of their registration. Motorists with cars registered in the United States are exempted. Quebecers who flee to the American Southeast each winter can receive a permit exempting them from the law for seven days if they return home without snow tires during the mandatory period.

While the law may make motorists safer, Quebecers are faced with an aesthetic issue. Owners of cars that ride on alloy wheels may opt for less costly, and more robust, steel rims for the winter, and may economize further by not buying wheel covers.

Some drivers, particularly those with all-wheel-drive crossovers, did not rush immediately to comply with the law. Ralph E. Warner, the director of operations for the Rubber Association of Canada, an industry trade group, said that although all-wheel-drive vehicles can often start in snowy conditions when shod with only all-season tires, after the vehicle gets going, “you need winter tires to remain on the part of the road you want to be on.”

As of 2014, only tires that carry a symbol of a snowflake inside a three-peaked mountain will qualify as winter tires. These tires must provide at least 10 percent more grip in medium-packed snow than an all-season tire, although most models generally exceed that requirement while also providing improved ice traction. The ministry will not accept models labeled “M+S,” indicating mud and snow, on the sidewall.

It does not appear that there are any immediate plans to enact similar laws elsewhere in Canada. Last month, the government of Saskatchewan, a particularly wintry province, rejected a similar mandate.