Thanks also for the info about the dog harness! I should check that out. She used to ride in a crate but then she got too big for our crate, and our cars were too small for a larger crate.
Sorry, this is totally not the right forum for this but since it was asked... I have a small dog and I have a seatbelt for him. They make them for big dogs, too and I would HIGHLY recommend them!!!
The one I have wasn't sold as a package, I bought the harness separately from the 'leash' part, but you can get some packages from PetSmart or similar stores that would probably work. I just liked that this harness had a chest-protector component.
This is the harness I have:
http://houndsaroundtown.com/travel/dog-seatbelt.html -it can be used for more than just the car, but I leave it in the car, actually attached to the seatbelt clip! (I got this from Pet Planet, not sure if you have one near you; they don't carry this at PetSmart. Manufacturers website which you can find a retailer through:
http://www.rcpets.com/rcpets/index.php)
And then because I didn't want to have to buckle up the seatbelt everytime or use the seat-belt latch (I didn't like the fact that with the seat-belt latch the attachment point is BESIDE the dog, he'd still be a projectile in a crash), I got this:
http://www.petsmart.com/product/index.jsp?productId=2755288 -my car doesn't have latch so I've rigged it so it is attached under the seat and comes up between the back & seat. Depending on the size of your dog, using it through the actual seat belt (as in the picture of the vest) might be a better option - my dog weighs only 12 lbs so I'm comfortable with our set up (oh, I should mention that my dog rides in the passenger front seat - he has separation anxiety and doesn't cope well with the back seat, but as with kids, the back seat is the safest place for dogs).
Whatever you do, be sure that you NEVER EVER EVER restrain a dog in a vehicle by a collar or a harness/leash not meant for this use. You could seriously injure or kill your dog or experience failure in the equipment which means the dog isn't restrained at all.
With the right equipment, and depending on your vehicle, you may be able to safely restrain your dog in the 'cargo' area of a vehicle such as an SUV or minivan, even if a kennel won't fit, which allows for more options with human passengers/car seats. But my personal preference is to put all passengers (human and otherwise) into a designated seat, with proper restraint.
Good luck!
Melissa
PS: What's interesting about the 3-in-1 Safety Harness is that it HAS been crash-tested (each size) at road speeds of 30mph (50km/h), which exceeds (in most cases) the testing on human car seats. The things that make you go hmmmmm.