"They become flying projectiles and when the car rolls, they're ejected just like humans are," says Dr. Marty Becker, with vetstreet.com.
Becker says having an unsecured pet is dangerous for the pooch and distracting to the driver.
"They need to either be in a carrier that's secured or they need to be in some kind of harness that secured to a seatbelt for their protection and for yours."
The safest place in that vehicle for your pet is the back seat. It's for the same reason it's the safest place for your baby: it's away from the passenger-side front air bag that explodes with such force that it can hurt a small child or pet in the front seat.
We all know dogs love to ride along with the heads out the window. Becker says that's a no-no.
"You've got to think of this: anything that's in the air - it doesn't have to be a rock, it can be a bug - when it hits their eyes at 60 miles per hour - it causes serious eye damage. So you can't have their heads sticking out the window."
Looking for a new vehicle? The editors at Edmunds.com just released a list of the Top 10 Pet-Friendly Vehicles for 2013.
For more information
Does My Dog Really Need a Seatbelt?
Pet Travel 101: What Every Savvy Dog Owner Should Know