It looks like I-PASS is a good investment for occasional tollway users. The deposit on a transponder is only $10, and with the cost of tolls cut in half, you'd recoup that investment quickly. More significantly, it's a lot more convenient than fiddling with cash, changing lanes at 70-plus MPH to get to the cash lanes, etc. Also, you can have multiple transponders under a single account and replenish your account automatically, which would simplify payments. My question is that the probability of my using different cars is pretty good. I have two cars, and although I probably don't use the tollway enough to justify it, I suppose that I could get a transponder for each one. But what if a friend comes over and says, "Let's take my car." Would we be able to use a transponder in my possession for the trip?