My rides are mostly out and back so locking is not an issue - though when riding alone I do carry a key lock and a chain, cut to belt length, around my waist. If I really need to stash the bike and walk back to the car, at least the bike has a ghost of a chance. That 1.5 lb chain is also good weight for training. When I drive a bike to work (going to ride after work, on the way home) I lock the bike to the trunk rack while it waits for the fun to begin. I also am in a parking lot off the beaten path and I park just outside the main entrance and the CCTV. No worries there either. If I'm heading to more worrisome places the bike goes inside the car, across the back seat.