Deaths on the nation's highways, which have been going down for years, appear to be on the rise again following a trend already firmly established in Sacramento County.
Traffic deaths in California and the United States have fallen every year since 2005. Sacramento County had seen declines, too, but deaths increased nearly 30 percent between 2008 and 2010, the last year for which final numbers are available.
Of the top 10 most populous counties in the state, Sacramento was the only one to show an increase each year between 2008 and 2010, California Highway Patrol data show. Most of those counties saw steady declines each year.
Now, preliminary data show that traffic fatalities for the state and nation may be on the rise again, too.
"Based upon the still-preliminary stats for 2011, we anticipate that there will have been an increase of 3 to 3.5 percent in overall traffic fatalities in California last year," said Chris Cochran, spokesman for the California Office of Traffic Safety.
And nationally, preliminary data from the National Highway Traffic Safety Administrations for January through March 2012 show that 7,630 people died in car crashes on the nation's roadways a 13.5 percent increase from the same period in 2011.
The increase represents the second largest year-to-year quarterly increase the NHTSA has recorded since it started tracking auto fatalities in 1975.
The recent increases have law enforcers and traffic researchers asking why with no easy answers at hand.
"We can't point to alcohol or drugs or motorcycles or red light runners or anything else specific that may have taken a jump," said Cochran. "We can only see the big, and still preliminary, picture. The telling will hopefully be in the details, when we can get them."
Typically, preliminary and final figures do not differ drastically. However, a clear picture will not be evident for at least a year.
Cochran cited a common explanation that declines and rises in traffic deaths are related to changes in the economy.
"If you look back in history and compare earlier crash declines to the national economy, you will see an almost quarter-to-quarter correlation, with crashes declining and picking back up again slightly behind recessionary ups and downs," he said.
Cochran said some of the declines would likely be a result of fewer miles traveled during a bad economy, but would not account for the whole decline.
"While we were seeing miles traveled declining in the 3 to 4 percent range, we were seeing fatalities dropping in the 10 to 12 percent range," Cochran said. "Plus, the decline in miles traveled only really lasted about two years, roughly 2007-2009. California's declines (in traffic deaths) started before and continued after."
The economy was also cited by Offer Grembek, researcher at the Civil and Environmental Engineering Institute of Transportation at UC Berkeley.
"The 2012 NHTSA data is a significant increase," said Grembek. "It's difficult to say what is causing it because we have not yet had a chance to look deep into the data."
Grembek studies how drivers adapt to safety and injury protections introduced into new cars by taking additional risks. He does not believe that technological and safety advances, and the risks they may spur, are at play in the early 2012 NHTSA data, or in the three-year fatality rate rise on Sacramento County roads.
Instead, he also suspects the rising fatalities stem from an increase in miles traveled as economic conditions improve.
"If more people drive, the number of fatalities will go up even if the individual trip is safer," he said. "The number rise does not suggest that the recession is over, but it has been shown in the past the these drops and increases happen around economic recessions."
Indeed, studies by the Federal Highway Administration and others have shown that recessions and increases in the price of fuel have affected fatality rates on U.S. roads. One well-quoted study concerning fatalities during the energy crisis found that during the 1974 oil crisis California traffic fatalities declined 25 percent more than researchers had expected.
For the CHP, one of the most troubling aspects in the rise in traffic deaths is that some of the fatalities may have been avoidable.
"During our enforcement periods we find that at least half of those killed were not wearing seat belts at the time of a collision," said Fran Clader, CHP spokeswoman. Last year 29 people died as a result of Labor Day weekend vehicle traffic accidents in California. Of those, 19 were not wearing seat belts, the CHP said.