It's no secret that distracted driving causes accidents. Most of the focus on distraction has been on texting and cell phone use. Now there's evidence that having your dog on board also leads to more car crashes, at least among the elderly.

Distracted driving is anything that could potentially remove your eyes from the road, your hands from the wheel, or your concentration from the task of driving. Dogs in cars would definitely fall into that category.

People who always drove with their pets had a crash risk nearly double that of people who didn't drive with a pet.

There's certainly anecdotal evidence that pets can cause car crashes by distracting drivers. Author Stephen King was struck and nearly killed by a van when its driver was trying to restrain his dog and lost control. But until now, there haven't been any studies testing whether such accidents are merely isolated incidents or are common enough to pose a significant hazard to drivers and pedestrians.

Researchers from the University of Alabama at Birmingham School of Medicine looked at the habits and driving records of 2,000 licensed drivers, 691 of whom were pet owners. They found that people who always drove with their pets had a crash risk nearly double that of people who didn't drive with a pet. Crash rates for people who sometimes or rarely drove with pets were similar to those of non-pet owners.

According to the authors, the elderly are more likely to be affected by pets in the car because their reaction time is slower than that of younger drivers. Previous studies have found that the elderly react more slowly when confronted with an increased physical or mental workload while driving. It's expected that this would also be true of their response to an active, moving animal.

Most of the pet owners who rode with their pets had them unrestrained in either the front or the back seat. Earlier research indicates that only about one in six people who drive with their pet use any type of restraint on them in the car.

In a 2010 survey by AAA, 20% of the respondents admitted to letting their dog sit on their lap while driving. Fully 31% said they were distracted by their dog while driving.

Currently, Hawaii is the only state with a law specifically restricting driving with a pet. That law prohibits driving with a pet in your lap. Should there be more laws like it? Well, that's asking a lot from the results of a single study. But the authors do suggest more study, among both the young and the old, to see of such laws are needed.

Until then, there are many products sold, including harnesses and doggie seat belts, that help keep a dog from becoming a distraction while still allowing them the freedom of the road. Like human seat belts, they also protect pets, stopping them from turning into guided missiles if a crash does occur. They're available from pet stores and online pet supply retailers.

An article on the study was published online in Accident Analysis & Prevention and will also appear in a future print edition of the journal.