Arizona's streets and highways grew deadlier last year, a reversal of historic declines in roadway fatalities. New state data show that 825 people died in traffic crashes in Arizona in 2011 -- one every 11 hours. The new numbers, released this week by the Arizona Department of Transportation, are sobering because they come just a year after both the state and country logged their lowest fatality rates ever.

Arizona's numbers had declined from 1,193 in 2005 to 759 in 2010. The 825 people killed in 2011 represents a 9 percent increase. In addition to the human toll, ADOT officials estimate that motor-vehicle crashes resulted in $2.9 billion in economic losses in Arizona.

Nationally, the number of deaths in 2011 fell by nearly 2 percent from the year before to 32,310, an all-time low that is nearly 26 percent below the 2005 number of 43,510 deaths, National Highway Traffic Safety Administration projections show. Historically, crash rates tend to rise and fall with the economic tide.

When times are good, more people take leisure trips and buy vehicles. Businesses deliver more goods. It adds up to more vehicles on the road and a greater chance of a crash. In rough times, activity ebbs, bringing crash rates down.

Safety experts say, however, that a variety of other factors have contributed to the most recent declines. They credit everything from tough laws and better enforcement to better engineered roads and cars. Decades of engineering progress has succeeded in making crashes more survivable as safety features in cars and on roads have improved, they say.

Although experts caution against reading too much into one year's worth of data, they say Arizona's 2011 numbers are alarming. Arizona's 2011 fatality record comes despite the fact that there were actually fewer people driving and fewer crashes. Alberto Gutier, director of the Arizona Governor's Office of Highway Safety, said the leading causes of fatal accidents are speeding, impaired driving, unused seat belts and inattention -- in that order. "The answer is enforcement, but you need officers to do that," Gutier said.

In 2011, the Arizona Department of Public Safety put fewer Highway Patrol officers on the road than in recent years, DPS spokesman Bart Graves said. "We're very concerned about fatal crashes going up," Graves said, adding that staffing shortages from retirements, hiring freezes, transfers and military duty all made 2011 a challenging year. DPS officials say enforcement saves lives because each ticket or stop is an opportunity to teach good driving habits.

There's logic to the argument, because four of the five leading contributors to fatal crashes stem from human behavior. As Graves says, highways and cars don't kill people; driver error does. The vast majority of Arizona's fatal crashes happened on straight, flat roads, in the daytime or on clear days, according to ADOT statistics. Graves and others cite distracted driving and fatigue as major problems. Mobile phones are more prevalent and smartphones offer more distractions.

Although Arizona does not track the number of texting-related deaths, some studies have likened the risks of texting behind the wheel to driving drunk. The types of crashes are similar, said AAA of Arizona spokeswoman Linda Gorman, explaining that texting crashes involve people going too fast or too slow, drifting out of lanes, or involved in rear-end collisions. "AAA believes that it's the mother of all distractions," she said, explaining that texting takes the eyes, hands and mind off driving. Other distractions affect fewer functions. Arizona is one of 11 states that does not have a texting ban, but research is mixed on the effectiveness of such restrictions. The NHTSA claims a quarter of all crashes are caused by inattentiveness, but those estimates are hard to verify.

Arizona also has no primary seat-belt law, meaning patrol officers cannot cite seat-belt noncompliance without suspecting another violation. And Arizona is among 39 states that don't require all motorcycle riders to wear helmets, according to the national Governors Highway Safety Association. ADOT's 2011 statistics show that in crashes where the drivers were wearing seat belts, only one-tenth of 1 percent of those drivers were killed. However, in crashes where the drivers weren't wearing seat belts, slightly more than 5 percent were killed. Meanwhile, 26 states saw increases in motorcycle deaths in 2011, the association found, and Arizona followed that trend, as well, increasing 55 percent, from 85 to 132.

"Motorcycle deaths continue to be a big part of the problem in Arizona," said Jonathan Adkins, the group's deputy executive director. "It's the one area where we really aren't making any progress." In attention from both cyclists and drivers is also the key factor here.