“[O]ur results provide strong evidence that the primarily enforced texting laws seem to be reaching the intended subpopulations who are most at risk for texting while driving,” they write.
The team examined 11 years worth of data from the 48 contiguous states for the study. They controlled for other factors that may influence crash risk, such as economic, legal and population-specific indicators. (Unemployment, for example, can influence risk because fewer workers means fewer drivers on the road. Income and gas prices can affect how much people drive, again exposing them to more risk.)
Just having a texting law was linked to a 2.3 percent decline in overall traffic fatalities for all drivers. But there’s a lot of variation in such bans. From 2000 to 2010, 31 states passed texting-while-driving bans, 24 aimed at all drivers and seven aimed at young drivers. Delaware’s was first — its law went into effect in April 2005 — while Wisconsin’s was last, going into effect in December 2010. And some laws only allow enforcement of the ban if officers have another reason for the stop, which is known as secondary enforcement.
The first of the researchers’ three main findings was that primary enforcement really matters.
“Our results indicated that primary texting bans were significantly associated with a 3 percent reduction in traffic fatalities among all age groups, which equates to an average of 19 deaths prevented per year in states with such bans,” one of the authors, Alva O. Ferdinand, said in a statement.
The second main finding is that targeting primary bans at subpopulations seems to be effective — primary bans aimed at teens reduced deaths among that group by 11 percent. Finally, they found that banning all handheld devices — i.e. laws that don’t specifically call out texting — were most effective at reducing traffic deaths among adults ages 22 to 64.
While 31 states passed texting bans during the 10 years studied, 44 ban texting among all drivers today, according to a late-June count by the bipartisan National Conference of State Legislatures. Thirteen states ban handheld devices.