7.5" AR pistol with Sig Brace travels with me most frequently.
Built from used parts, I'm not out much money if it gets stolen.
Longer trips, I bring the Tavor.
These short rifles fit nicely behind the passenger seat with the rear seat folded forward in my truck.

In the traffic jam scenario, I would be concerned with the guy three cars behind me, shooting me in the back if I stepped out and started firing on the beabs.