Somewhat related to this thread, but certainly to dogs in cars... I've always been concerned about what would happen to my dog in a collision. Not just to him, but also to me or other passengers if he was bouncing around the cabin. After some research, I came to the conclusion that most of the doggy seat belt devices out there are pure garbage... except for one. The Center for Pet Safety wrote up their test results here:
http://centerforpetsafety.org/wp-content/uploads/2013/07/2013_cps_harness_study_summary_final.pdf
The only harness that passed the test was the Sleepypod Clickit Utility.
They have since updated the 'utility' with the 'sport', which is apparently easier to get onto the dog... an requires less fiddling with the belt etc (no child seat tethers any longer). I bought one a few months ago and am happy with the construction. My Dood?? Not so much... he liked the freedom to roam around the back seat! But he's stuck wearing it now.
Obviously, I have no connection with the supplier. Just wanted to share in case others want to get their dog into a harness system.