Two Carnegie Mellon University scientists are warning people that there's much more to daylight-saving time than just setting your clocks back an hour tonight.

You need to get your mind right.

Professors Paul Fischbeck and David Gerard have made a study of traffic fatalities that shows pedestrians walking during the evening rush hour are nearly three times more likely to be struck and killed by cars in the weeks after the fall time change.

The problem, they suspect, is that pedestrians and drivers have gotten used to more than six months of visibility during those hours and are slow to adapt to the danger of the darkness.

"The change that's going to occur on Sunday is going to have some pronounced effects on your risks of walking between 5 p.m. and 7 p.m.," Dr. Gerard said last night. "Basically, these are the hours when it's just getting dark. Next week at this time, it will be pitch black. But people walking and people driving won't have adjusted. The baseline risk for getting killed is almost tripled."

Their study of pedestrian fatalities from 1999-2005 shows that there is an average of 37 more U.S. pedestrian deaths around 6 p.m. in November compared to October. That amounts to an increase of 186 percent.

No such jump was seen for drivers or passengers in cars.

"It's astonishing," Dr. Gerard said of the data. "It's particularly worse right at the switch date, [when the average increases] two people a day for the next couple weeks, until the adjustment is made."

Dr. Fischbeck, of Oakland, regularly walks with his 4-year-old twins around 6 p.m. He said he is worried enough that he'll be more cautious starting Monday.

"A three times increase in the risk is really dramatic, and because of that we're carrying a flashlight," he said.

"I cross the street at Beechwood over to Frick Park twice a day," said Dr. Gerard of Squirrel Hill, "and I really think people don't adjust. That's just my observation."

But the statistics back it up.

"There's no significant difference at noon, but there is at 6 p.m.," Dr. Gerard said.

After spiking sharply in November, the number of pedestrian deaths at 6 p.m. begins to drop in December. The danger declines each month.

Once everyone "springs forward" to daylight-saving time in April, there is a 78 percent drop in risk at 6 p.m., they said.

"Our goal of the project is to educate people about things so they can act to reduce their own risk," Dr. Gerard said. "We want people who are now walking at dusk or driving at dusk to keep this in mind and make adjustments and think about what they're doing. It might save somebody's life.

"You can't go about your business in the same way when people can't see."

This isn't the first study of pedestrian deaths during the switch from daylight-saving time to standard time. Research by The Insurance Institute for Highway Safety of Arlington, Va., has calculated that going to a year-round daylight-saving time would save about 200 deaths a year, spokesman Russ Rader said.

"Benjamin Franklin conceived of daylight-saving time as a way of saving candles," Mr. Rader said yesterday. "Today we know it saves lives."

The risk at 6 p.m. in November, after daylight-saving time ends, is 11 times higher than the risk for the same hour in April, when daylight-saving begins, according to the Carnegie Mellon researchers.

Pedestrians also appear to be safer when walking in the morning.

Dr. Fischbeck and Dr. Gerard used federal traffic fatality data that they've incorporated into a searchable database for different risk factors. Their analysis was not peer-reviewed and is not being published in a scientific journal.

But it does jibe with other peer-reviewed studies that looked at raw fatalities.

A 2001 study by John M. Sullivan at the University of Michigan looked at national traffic statistics from 1987 to 1997 and found that there were 65 crashes killing pedestrians in the week before the clocks fell back and 227 in the week after.

But overall for the evening rush hour, turning the clock back is a killer. In seven years there have been 250 more deaths in the fall and 139 fewer deaths in the spring.

"This clearly shows that both drivers and pedestrians should think about this daylight-saving adjustment," Dr. Gerard said. "There are lives at stake."

First Published: November 3, 2007, 4:00 a.m.