A series of back-and-forth shifts in highway fatality rates over the last several years is highlighting, to a degree, the inverse impact of weather conditions on crash risk as well as concerns that the effect of distractive driving on fatality rates may be underreported.

“We’ve seen this before when we’ve looked at fatality data; milder winter weather usually results in a sudden ‘shooting up’ in highway crash fatalities,” John Ulczycki, vice president of strategic initiatives at the National Safety Council (NSC), told Fleet Owner. “That’s because more people drive in milder weather compared to snow storms, thus their ‘crash exposure’ risk increases.”

That’s why the 3% increase in deaths on U.S. roadways from 32,479 in 2011 to 33,561 in 2012 analyzed by National Transportation Safety Board (NTSB) -- which led Deborah A. P. Hersman, NTSB’s chairman, to declare the U.S. “has serious public health and safety epidemic on our highways” two weeks ago – then dropped 3% from 2012 to 2013, according to NSC’s research.

“The worse the weather is, the less people drive and thus the less exposure to the risk of a crash,” NSC’s Ulczycki said. “It’s kind of counterintuitive as one would expect more fatalities in bad weather. That’s what that spike in fatalities for 2012 we believe is a one-year aberration due to the weather conditions.”

More troubling, though, is that the NSC’s analysis indicates that while highway fatalities declined 3% in 2013 from 2012, they remain 1% above the fatality numbers recorded in 2011.

“More than 90% of crashes are due to human error,” Ulczycki pointed out. “Drivers are taking a lot of risks on our roads today; people are speeding, driving impaired from alcohol and drugs, not wearing seat belts, talking on phones, reading or sending email and texts, and parents are letting teens drive before they are ready.”

Yet he added that the impact of distracted driving may be muted due to the way law enforcement agencies “code” the cause of motor vehicle crashes.

“The cause of the crash may be coded to running a red light or to speeding, but were ‘distractive behaviors’ the reason why the driver ran a red light or was speeding? That’s one reason why we think while fatalities declined in 2013 from 2012, they still remained higher compared to 2011.”

That reasoning is also why NSC is voicing concern over the rapid growth of what it calls “voice-operated in-vehicle infotainment” systems.

“The rapid advancement and adoption of communications technology has resulted in a new and dangerous level of driver distraction,” noted David Teater, NSC’s senior director of transportation initiatives during a day-long summit on distracted driving hosted earlier this month by the U.S. Senate’s Commerce, Science and Transportation Committee.

“It is likely that technology can go a long way in reducing distraction; however, if we continue down the current path of enabling drivers to engage in all sorts of infotainment and communications activities, we may be normalizing a dangerous practice that will be difficult to unwind in the future,” he stressed.

Teater added that motor vehicle crashes remain the leading cause of death for a large portion of the U.S. population, with approximately 100 people are killed every day in such crashes. Vehicle crashes also present a significant national cost in lost wages and productivity, medical expenses, administrative expenses, employer costs and property damage, according to NSC; a cost that reached $267.5 billion in 2013, a 3% decrease from 2012, according to the group‘s data.

“We recognize there is a mad rush toward communications technologies and we don’t want to stop any kind of technology development,” Teater emphasized. “We simply want them to be used at the right time and place, and driving a vehicle is not the right time or place to do anything not related to driving.”