The number of people killed in U.S. traffic accidents fell by 4.2 percent during the first six months of 2013, according to data released by the National Highway Traffic Safety Administration (NHTSA).

The agency says 15,470 people died in motor vehicle crashes during that time, compared with 16,150 fatalities during the first half of 2012. That works out to a rate of 1.06 deaths per 100 million miles traveled, as opposed to 1.10 for 2012.

Unexpected figures

Those figures were a surprise to transportation experts, who’d predicted that fatalities might rise as the economic recovery continues and Americans participate more in activities that require them to go places. Traffic deaths hit a peak in 1972 and declined in the following years, only to experience a 4.4 percent surge in 2012 – to 33,780 deaths.

Government officials say the recent drop could be related to technological improvements in:

• Airbags
• Collision avoidance systems
• Passive safety systems
• Vehicle design and
• electronic stability control, which is now required in all new vehicles

Motorcycle fatalities way up

One exception to the trend: a dramatic rise in motorcycle deaths that corresponds to the elimination – in some states – of mandatory helmet laws. Michigan, for instance, saw an 18 percent increase in total motorcycle fatalities in 2012.