Car-deer crashes are rarely fatal for the motorist, but they are numerous in South Dakota, especially during autumn months.

The state Department of Transportation reports that a vehicle hitting an animal - almost always a deer - was the second most common cause of highway accidents in South Dakota in 2005. Slightly more than 30 percent of car crashes statewide that year were attributable to deer.

Nationally, there are an estimated 1.5 million crashes involving deer and vehicles every year, with more than 200 human fatalities and 29,000 human injuries annually.

In South Dakota, no one has died in a deer-car collision since 2004, when four people were killed in a crash precipitated by an animal, but last year there were 5,013 car accidents caused by animals in the state.

Never are the risks higher than in the two coming months. Fall is upon us, and drivers have good reason to be vigilant about deer.

In 2006, October saw 597 car accidents and November saw 1,062 accidents involving deer in South Dakota, according to state accident records. Deer-car accidents typically range between 200 and 400 most other months of the year.

Decreasing hours of daylight and increasing numbers of deer can be a potentially fatal combination. The numbers rise as more deer migrate to mate and find winter range in the fall. In mountainous areas, deer move to lower ground, descending to places where it is easier to find food and, unfortunately, crossing roadways in the process.

The state DOT is analyzing the effectiveness of deer reflectors - roadside reflectors installed a series of posts - that are thought to create a "fence" of reflected light that deer avoid. TheDOT should continue to explore other methods - from high-tech infared lights and lasers to low-tech fencing options.

In the end, however, preventing deer-car collisions will continue to be the responsibility of drivers who must be alert and responsive to deer behavior - especially at this time of year.