WASHINGTON

One night several years ago, my mom slipped and broke a bone in her neck. I stayed late at the hospital with her. Driving home on a mostly deserted road, I checked my cellphone messages.

I didn’t notice either the red light coming up or the car stopped at the light. I banged into the back of it, and even though the damage was minor, it was a scary moment.

I admitted that I was upset and distracted, took the blame and swore to myself I’d never use a cellphone in a car again. But, of course, I did. D.C. police will pull you over if they see you using a cellphone that you’re holding up to your ear, but not if you’re hands-free.

Ominously, research by the National Highway Traffic Safety Administration  suppressed for years and released on Tuesday after petitions were filed by advocacy groups  shows that there are “negligible differences” in accident risk whether you’re holding the phone or not. Hands-free devices may even enhance the danger by lulling you into complacency.