Man’s best friend is not a driver’s best friend. While lawmakers have been banning drivers from texting or using cellphones, many motorists are riding around with another dangerous risk -- their dogs. Experts say an unrestrained dog -- whether curled up on a lap, hanging out the window or resting its paws on the steering wheel -- can be deadly. Tens of thousands of car accidents are believed caused every year by unrestrained pets, though no one has solid numbers.