The number of people killed in vehicle crashes in the United States declined last year, except in the areas of Arizona, California and Hawaii.

The reasons for the decline seem to have more to do with the economy than any particular focus on safe driving. This comes despite a series of calls to ban distracted driving nationwide and efforts ate increasing teenage driving awareness and safety.

The fact is, during a down economy and with gasoline prices rising, people are naturally driving less. The less they drive the fewer opportunities they have to be involved in a serious (or any kind) of vehicle crash. The fewer crashes, the fewer deaths. The math isn’t hard to calculate.

There is also something to be said for the increase safety of today’s vehicles and improvements being made to roads, intersections, bridges and highways which create a safer environment for drivers.

It is a little bit more difficult to understand why these three areas have outpaced the national average however. What forces are at work in these three states which have caused traffic fatalities to increase while nation wide traffic fatalities are down?

That is a question California traffic experts are trying to figure out:

Last year’s national decline in traffic fatalities — to 32,310 — came as motorists drove about 36 billion, or about 1.2%, fewer miles, perhaps because of high gas prices and a still-difficult economy that might have discouraged pleasure road trips.

The 2011 fatality rate is projected to decline to the lowest on record, to 1.09 fatalities for every 100 million vehicle miles traveled, according to the National Highway Traffic Safety Administration.

Traffic deaths have fallen by about 26% since the 43,510 fatalities reported in 2005; highway fatalities peaked in 1972, at 54,589. In 1949, there were 30,246 fatalities, but the rate was 7.13 fatalities for every 100 million vehicle miles traveled.

Traffic safety experts attributed the decline to a number of factors — “probably people driving less, safer vehicles, safer roads and an improvement in the safety culture across the United States,’’ Jacob Nelson, director of traffic safety advocacy for the AAA national office, said in an interview.

Jonathan Adkins of the Governors Highway Safety Assn. cited increased seat belt use, safer cars, better roads and an improved emergency medical service response effort. “Also, the economy continues to keep traffic deaths lower than normal,” he added.