CEDAR RAPIDS — Midway through the year, 41 fewer people have died in Iowa traffic crashes than a year ago.

As of July 1, the Iowa Department of Transportation daily traffic fatality count showed 136 people died on Iowa streets and roads in the first six months of the year, 33 fewer than the mid-year average of 169 for 2007-12.

It’s hard to pinpoint a reason for a year-to-year increase or decrease, but Denny Becker of the Governor’s Traffic Safety Bureau thinks general improvements in the way cars are built are a significant factor.

“Cars are made better,” he said. “They hold up better in crashes. They’re stronger, especially the cab areas, than they were in the past. People are buying cars that are safer.”

Sgt. Scott Bright of the Iowa State Patrol points to Iowa drivers’ 94 percent compliance rate with state seatbelt laws. Better vehicles and better roads certainly are factors, too.

“You can’t really focus on any one thing,” Bright said.

Steve Gent of the DOT’s traffic and safety office agrees.

He attributes the decline, in part, to the economy. Instead of steady increases in the number of miles traveled on Iowa roads, he said online shopping and telecommuting are having an impact.

“It’s the overall economy,” he said. “We’re not driving more.”

Also, Gent said, it’s important to understand that the numbers are relative. Compared with last year, the numbers look great, but the July 1 number is just six less than two years ago.

“Remember, fatal crashes are very rare occurrences, and the number of fatalities can vary greatly from month-to-month and year-to-year,” Gent said. “You have to look at the trend, and it’s looking good.”

Both Bright and Becker mentioned distracted driving as a growing problem.

“People are tweeting going down the interstate,” Bright said. “I see people reading emails on their way to work. I tell them that email will be on their office computer if they get there.”

More than half of the difference between this year and last occurred in May when crash-related fatalities fell from 48 in 2012 to 24. Bright speculated that rainy, cool weather may have kept people closer to home and many motorcycles in garages rather than on roads.

A fatality is considered “crash-related” when death occurs within 30 days of a crash, the DOT said.

In January, there were 17 fatalities compared with 39 in the same month of 2012. The number of fatalities was higher in April and June of this year than the same months last year.

The DOT said the “Life Toll” — the number of people who have escaped serious injury or death because they were buckled up at the time of the crash, as determined by the investigating law enforcement officer — was 65 for the first six months of the year.

In roughly a third of the fatalities, the victims were using seat belts, according to the DOT. In another third, they were not.

Although last year there were no fatalities on the Fourth of July, the holiday typically is the second or third deadliest holiday on Iowa roads. Labor Day weekend is the deadliest.