The number of deaths from motor-vehicle crashes declined by 5 percent during the first six months of 2013 compared with the first six months of 2012, according to preliminary data collected by the National Safety Council.
The council estimates that 16,620 traffic deaths occurred from January through June, compared with 17,430 deaths during the same period last year.
The council said it has not identified "definitive reasons" for the drop in traffic fatalities.
"The council will be keeping a close eye on our monthly traffic-fatality estimates to determine if this decrease is just a blip on the radar," said Janet Froetscher, president and CEO of the National Safety Council. "We are encouraged to see this downward trend and will remain vigilant to keep our roads as safe as possible."
In addition to the loss of human lives, the cost of motor-vehicle crashes includes lost wages and productivity; medical and administrative expenses; and property damage.
The cost of motor-vehicle deaths, injuries and property damage through June was $127 billion, according to preliminary data from the National Safety Council.
The council estimates that there were 1.8 million medically consulted motor-vehicle injuries during the first six months of 2013, up 2 percent from 2012.