|Steve Baker -- this traffic is for the dogs (Flikr)|
One thing to realise, however, is that the current products being sold as "dog seat belts" are not subject to any real performance testing, and when tested many show catastrophic failures. That is to say, they break when subjected to a sudden force. Most manufacturers report that their products pass some kind of "crash test", but these are whatever the maunfacturer deemed sufficient, not an independent test against empirical standards.
The only brand to acceptably restrain the dog on comparsion testing by the Center for Pet Safety (Subaru) was the Sleepypod Clickit Utility (not an affiliate link). But consideration should also be given to how the design of the harness and point of attachment of the tether can cause more serious injuries ot the dog than of the were unrestrained even when the product does successfully restrain the dog's motion.
Currently most canine vehicle restraints are not tested for either their effectiveness or their actual safety for the dog, and use of properly anchored travel crate may be safer.
- Zeleny, M., and K. Grusova. "A car accident involving a restrained dog within the vehicle: a case report." Veterinarni Medicina 60, no. 7 (2015): 399-402.