Yes you can fit a double bass in your car.

First, put the front passenger seat all the way back, then tilt the seat back.

Put the bass in neck first, strings away from you. Work the neck around so it sticks out over the back seat or shelf. The bass stays on its side, bridge facing the driver.

Manoeuver the lower bout so that it is fully supported on the seat, and then raise the front seat-back up to support the upper bout shoulders. The neck should not actually touch the back seat or shelf.

Wonderful. Now get in to the driver seat, adjust the bass so that it leans slightly over against the passenger window and won't tip on you when you go around a corner.

See you tomorrow!