You would think the trigger lock would suffice, but then you would live somewhere else! It is a forgivable mistake in that common sense moved to a free state years ago. The above posts are correct as to high cap / low cap transport. Even if your in compliance, who wants to go through the ordeal that's coming if the vehicle were broken into and the rifle stolen!
If you live somewhere else, you don't own trigger locks. Again, I ask what this mass obsession with trigger locks is. Just amazing. As was already pointed out, they serve no purpose during transport and very little purpose even at home, other than simply making you compliant with a stupid law.
I will occasionally leave a rifle in my car for a few days in the hope I'll get time to stop by the range. But I only do that because my specific situation is very low risk.
My car is parked in a locked, alarmed, garage when I get home from work.
At work, my car is parked in a campus with guards.
Also, my car has a trunk, and its trunk can be completely secured. The rear seat fold down release is in the trunk and if I lock the glove box, the car disables the electric trunk release. So the only way to get into the trunk is to crow bar it open. For what its worth, the security of this car's trunk was one of the reasons I bought it.
When I had a hatch, I wouldn't ever have a gun in it unless I was going to the range, in which case all the guns were in the drivers side rear seat.