PITTSBURGH - When fall comes around, a buck's fancy turns to mating and that means an increase in collisions between deer and motorists.

While accurate numbers are hard to come by because not all police departments track collisions and many accidents are not reported, the Insurance Institute for Highway Safety estimates that about 1.5 million collisions occur each year.

About 150 people are killed in deer collisions annually, and collisions cause more than $1.1 billion in vehicle damage, according to the institute.

Pennsylvania's deer population numbers between 1.3 million and 1.5 million, according to the Pennsylvania Game Commission. A commission study found 90 percent of all deer are conceived between mid-October and mid-December, which also coincides with the increase in deer-vehicle collisions.

During mating season, a male deer "will be oblivious to everything else around it. They'll walk out in the middle of a highway with an 18-wheeler. They're focused on that (doe) scent trail," said Jerry Feaser, a commission spokesman.

But mating pressure alone doesn't account for all accidents.

People enjoying the outdoors, farmers and hunters all move deer, Feaser said.

The switch from daylight-saving time to standard time on Sunday also means the evening rush hour will coincide with dusk or just after dark - one of the times deer are most active, Feaser said. Deer are also active around sunrise.

In Pennsylvania, which has a high deer population, 14 people were killed last year in deer collisions. The number has been increasing over the past five years, from two in 1999 to 12 people in 2002, according to the Pennsylvania Department of Transportation.

Between 1997 and 2001, the most recent figures available, the number of reportable accidents - those involving either injury or damage severe enough to warrant a police report - increased from 2,079 to 2,532. In 2000, 2,566 reportable accidents occurred.

"Obviously, the number of deer struck each year is dramatically higher than that," said spokesman Steve Chizmar. The Game Commission estimates between 45,000 and 60,000 crashes a year.

Chizmar attributes the increase in part to more people living in more rural areas. "For that reason, the possibilities of encountering a deer on the road are going up," he said.

Erie Insurance Group has studied deer-vehicle collisions and warns customers to be alert around this time of year, though Darrin Birtciel, an actuarial analyst, can't say if that's responsible for a recent slight decrease in claim frequency.

"We look at it from the standpoint that the more information we know about the claims that are occurring, the better job we can do to trying to reduce their frequency" to keep rates down, he said.

Last year, Erie Insurance paid out nearly $60 million for 29,000 claims filed by customers - about $2,040 per claim. Erie Insurance insures 2.4 million vehicles and deer claims account for nearly 40 percent of its comprehensive losses.

"You can be the most careful driver and the deer can come out and run into the side of your car," Birtciel said.

Drivers, however, can reduce the likelihood of hitting a deer. Erie Insurance advises motorists to use high beams when possible, which will at least illuminate deer.

Chizmar also said motorists should also heed "deer crossing" signs. "Those signs are put there for a reason," he said.

One thing that isn't believed to work, anecdotal claims to the contrary, is the deer whistle.

"There's isn't any evidence that they reduce crashes at all," said Russ Rader, a spokesman for Insurance Institute for Highway Safety, which has studied their effectiveness.

He said it's unclear if deer can hear them, and even if they can, "there isn't any evidence that they react to them."

In Pennsylvania, motorists aren't required to report a collision to the Game Commission, though Erie Insurance suggests it.

Pennsylvania residents may keep a deer carcass, but must call the commission to receive a free permit within 24 hours of picking up the deer. Antlers from bucks must be turned over to the commission.

Motorists are more likely to hit a deer from mid-October to mid-December. Some tips to try and avoid collisions:Wear your seatbelt and stay alert for deer, especially during the peak hours from sunset to midnight and the hours shortly before and after sunrise.Use high-beam headlights when there is no opposing traffic. The stronger lights will illuminate the eyes of deer, but won't necessarily scare them away.Deer whistles, deer fences and reflectors don't always deter deer. Don't rely on them to keep you safe.If you see a deer in the roadway, slow down and blow your horn. If the deer doesn't move, stop and don't drive until the deer moves. Also, try not to slow down or swerve into the opposing lane; many accidents happen when someone swerves to avoid a deer, but ends up hitting another car.Deer frequently travel in groups. If you see one on the road, be alert for others in the area.Do not approach an injured deer. The animals have sharp hooves and can cause injuries.If you do hit a deer, report the accident to the Pennsylvania Game Commission or local law enforcement officials.SOURCE: Erie Insurance Group.