Well that's a very good question Colin! Not having been there lately, that's something I've been thinking about especially. If it's wet he'll have to take the car.
If I do it in Rossi colours I shall have to attempt both front and rear mudguards, plus perhaps a complete fairing to keep everything dry!
Looking at it again, if Batman tries to back up anywhere the cape will get caught in the rear wheel!
The other answer is the movie people didn't think of that either!