The current lack of consensus about distracted driving in the US has one advantage, say scientists at Temple University - it means it'll be easier to work out which laws make sense and which don't.
"We know that distracted driving is dangerous, yet despite the diffusion of distracted driving laws, there is evidence that driver use of mobile devices is increasing," says Jennifer Ibrahim, an assistant professor of public health in the College of Health Professions and Social Work.
With cellphone distractions accounting for more than 300,000 car crashes each year, most states have put some sort of legislation in place to limit or prohibit the use of mobile devices while driving.
But unfortunately, says Ibrahim, there's a widening gap between the evidence on distracted driving and the laws being passed to address the problem.
Ibrahim and her team analyzed distracted driving laws passed between January 1, 1992 and November 1, 2010, and found there was an enormous variation from state to state.
Some base their laws on the type of mobile device being used - whether a cellphone, laptop or tablet computer - with others making distinctions on the category of drivers, such as by age or by driving permit type, and still others basing their laws on the type or location of mobile device use.
Enforcement and penalties also vary from state to state; as of November 2010, 39 states plus Washington DC have one or more laws restricting use of mobile devices while driving, while 11 states have no laws at all.
And the researchers point out that there is no systematic review currently in place to evaluate distracted driving laws or provide evidence on their effectiveness.
However, says Ibrahim, from a research standpoint, the variation is helpful – it means it's possible to compare legislation from state to state to identify for future research which restrictions are the most effective.
"Our study is the first step toward understanding which laws really do reduce distracted driving, and thus can reduce related crashes and associated injuries and fatalities," she says.