Image: Car accident © Robert J. Bennett, age fotostock

The Fourth of July may be the most hazardous day on U.S. roads, but Aug. 1 kicks off the deadliest month of the year for American motorists.

According to National Highway Traffic Safety Administration records going back to 1994, more Americans die in car crashes in August than at any other time of the year. Though the number of people killed in U.S. crashes in August 2009 dropped by almost 400 from 2008, 2,864 still died during the month. (The total for 2010 isn't yet available.)

The traffic safety agency reports that per 100 million miles traveled, August has an average fatality rate of 1.09, compared with 1.08 for September, the second-deadliest month, and 0.94 for March, the safest month. July, at 1.04, is the third-deadliest.

In 2009, the agency says, an average of 93 people died each day in U.S. motor vehicle crashes -- an average of one death every 16 minutes. And according to the Insurance Institute for Highway Safety, from 2005 to 2009, seven of the 25 deadliest days overall occurred in August.

The odds of a fatal crash increase in August "because more people are out on the road driving more miles than other times of the year," says Russ Rader, a spokesman for the institute.

The deadliest day and the safest day

For the same reason, the deadliest days are on the weekends. Since that's when Americans tend to run extra errands, visit family members or take more day trips, and when drunken driving increases, it's no surprise that weekends are a more dangerous time to be on the road.

Saturdays have the most crash-related fatalities, with Saturdays in 2009 averaging 123 deaths a day nationwide, according to insurance institute data. Sundays were the second-deadliest in 2009, with an average of 107 deaths, followed by 102 on Fridays.

By contrast, Tuesday is the day you're least likely to die in a crash, with an average of 69 fatalities occurring each Tuesday.

The rest of the daily averages:

  • Mondays, 79 deaths.
  • Wednesdays, 78.
  • Thursdays, 84.

The deadliest and safest days of the week

The Insurance Institute for Highway Safety says 32% of crash deaths occur between 3 and 9 p.m. But the National Highway Traffic Safety Administration has narrowed down the deadliest hours to between 6 and 8:59 p.m. That's when more than four people die each hour, according to the traffic safety administration.

"A large proportion of crashes happen in late afternoon and early evening in general, but especially in August," Rader says. That's when the roads fill up both with commuters and vacationers.

It's no surprise that from 3 to 5:59 a.m., when most people are snuggled in their beds, is when the fewest deadly crashes occur. But that doesn't mean it's entirely safe on the roads: A little less than an average of two people die each hour.

The morning commute is only slightly more deadly, still averaging between two and three deaths per hour between 6 and 8:59 a.m.

Middle of the day, middle of the road

The insurance institute says 23% of all U.S. crash-related deaths -- an average of three per hour -- occur between 9 a.m. and 3 p.m.

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One reason for the nation's death rates: Despite decades of safety campaigns, millions of motorists don't always buckle up. For example, less than half of drivers and passengers between ages 13 and 54 use seat belts, according to numbers crunched by the traffic safety administration.

"If everyone buckled up on every trip, we would sharply reduce the number of fatal crashes that we expect to happen this summer," Rader says.

Who's most likely to die in an accident?

According to the insurance institute, 33,808 people were killed in crashes on U.S. roads in 2009:

  • Ages 13 to 15 constituted 2% of all traffic deaths.
  • 16 to 19, 9%.
  • 20 to 34, 31%.
  • 35 to 49, 23%.
  • 50 to 69, 22%.
  • 70 and up, 12%.

Children under age 13 accounted for less than 1% of traffic deaths, which can be attributed to the increased use of infant and child safety seats in recent decades. In 1975, 8% of all traffic deaths involved kids under 13.