The wrong mix of winter weather and traffic along the Wasatch Front can spell disaster - and does frequently - as motorists face the uncertainties of ice and snow on interstate highways and other thoroughfares.

Commuters who travel the same stretch of road day in and day out become better acquainted with some traditional trouble spots, but Utah Highway Patrol troopers say commuters also may become callous to warning signs and speed pell-mell into a pileup on a stretch of road they travel hundreds of times a year.Veteran Utah Highway Patrol troopers confirm there is a reasonably well-defined list of trouble spots in Salt Lake and Davis counties where pileups and deadly accidents are most common.

Most of the troopers the Deseret News talked to identified overpasses - like the I-15/I-215 interchange in Murray and the Beck Street overpass south of the Salt Lake/Davis county line - because bridges are the first to freeze and be covered with black ice when the weather is bad.

All of U.S. 89 in Davis County worries law enforcement officials. Most other specific locations on the troopers' lists have particular engineering quirks or are in locations where fog or ice crystals are a recurring problem. (See chart.)

Fog is a problem on I-215 in Murray where an overpass east of the Redwood Road exit crosses the Jordan River. Some 67 cars piled up in the fog there on Dec. 28. McKinnon said that's also the fastest section of interstate in Salt Lake County. The most recent speed check there showed the average speed is 62.5 mph.

Sixteen cars were involved in three adjacent accidents in thick fog on the 21st South freeway when a semitrailer truck pulled out of the truck stop at 6381 West and was pelted by vehicles whose drivers couldn't see it blocking both of the eastbound lanes.

UHP Sgt. Les Langford said the problem there is so frequent that troopers plan to lobby the Utah Department of Transportation to restrict the intersection and reroute trucks to the overpass at 56th West.

Two Davis County intersections that carry a heavy volume of traffic were left off the troopers' list:

-The Hill Field Road and U.S. 89 intersection, a T-intersection at the top of the hill above Weber Canyon, has been earmarked as one that should be replaced with a full interstate-style interchange. Although it carries heavy traffic and cars that turn north into Ogden from Hill Field Road line up for a half-mile sometimes, the accident rate is fairly low. Most drivers are afraid to take chances.

-The U.S. 89-Burke Lane and I-15 intersection in Farmington. The overpasses ice up in the winter and traffic is heavy, but accidents there are usually limited to one or two cars, mostly sliding off the road.

The exceptions, though, can be spectacular. The freak October 1985 snowstorm that dropped 18 inches of snow turned the whole interchange into a skating rink, resulting in a 95-car accident and a pile of accident report forms that stacked 18 inches high. And, wind gusts at its location at the mouth of Farmington Canyon regularly top 100 mph during canyon wind sieges - gusts that have blown freight trains off the tracks.

The biggest pileup Langford has handled in his 17 years on the road was on the south side of the Point of the Mountain when 243 cars tangled in both the northbound and southbound lanes. Black ice and fog were blamed.

Langford said he got an idea of how that mess got started when he visited the area the next day and clocked cars driving through the fog and on black ice at anywhere from 25 mph - which was probably too slow - to 75 mph - obviously too fast.

"You just hope the two don't meet in the same lane."

Trouble

Utah Highway Patrol Sgt. Les Langford says motorists could help by knowing the signals.

A trooper will activate the patrol car's flashing yellow warning lights while on a routine traffic stop or when helping a disabled motorist. But red and blue overhead lights or flares on the road mean trouble ahead.