How about some crash test results?
2013 Harness Crash Test Videos2015 Crate Study ResultsSecuring Pet Carriers –
While it is intuitive for most people to “buckle up” their pet’s carrier – DON’T! – unless the manufacturer provides you with crash test video to illustrate structural integrity. Using a seatbelt to secure a carrier can actually crush the carrier if you get into an accident.
Instead – put the small carrier on the floor of the vehicle behind the front passenger or driver seat.
Source: Center for Pet Safety