Cellphones present one of the thorniest problems that lawmakers must deal with, according to information from the Insurance Institute for Highway Safety (IIHS). Once simple communication devices, they’re now cameras, GPS navigators, web browsers, game consoles, diet trackers, payment portals, stock-trading platforms, social media spaces and more. In general, states have taken two approaches to deal with the expanded potential for distracted driving, either attempting to enumerate all the forbidden operations or drafting broad prohibitions against holding or using a phone or similar electronic device while in the driver seat on a public road.

It’s common knowledge that texting while driving is illegal in most places. But what about tapping the screen of your cellphone to accept a faster route suggested by Google Maps? What if your phone is mounted on the dashboard? What if you’re stopped at a red light? Is tapping the screen of your phone different from tapping your car’s touch-screen infotainment center? Drivers have varied interpretations of what is acceptable — and so do state laws and the police who enforce them.

“Technology is moving much faster than the laws,” says Ian Reagan, a senior research scientist at the IIHS. “One solution may be to make them broader, rather than trying to come up with an exhaustive list of banned behaviors.”

In a recent paper, IIHS researchers examined crash rates in three states that adopted the latter strategy to determine if such broad laws are having the intended effect. The answer?

“As my daughter might put it,” says Reagan, “it’s complicated.”

Rather than look specifically at crashes attributed to distracted driving, which tends to be underreported in police records, Reagan and his colleagues examined the laws’ effect on police-reported rear-end crashes. Rear-end crashes were chosen because past research has shown that cellphone use is associated with a much larger increase in the odds of those crashes than any other type.

They found that monthly crash rates per 100,000 people dropped substantially in Oregon and Washington after those states adopted laws against holding a phone while driving. However, California failed to achieve the same gains.

“The mixed results suggest that broader cellphone laws can work, but the specific wording and other factors like the severity of the penalties seem to make a difference,” Reagan says.

California, Oregon and Washington all broadened their laws in 2017. Each state added language that ensured that the only acceptable cellphone interaction was via hands-free systems that required minimal manual input. Oregon and Washington banned any “holding” of a cellphone and specified that the bans apply to times when the vehicle is stopped temporarily because of traffic or other momentary delays.

California’s law used similar general language, but it did not state whether its ban applies to times when the vehicle is stopped temporarily. Also, by prohibiting “holding and using” a cellphone, rather than simply “holding” one, it made it possible, at least theoretically, for a cited driver to argue that they were holding their phone but not using it, and therefore weren’t violating the law.

Now you can see how difficult a task lawmakers face in wording traffic laws.