We've had them on both sides for the last 15' after our dryers. Yes they need cleaning on a regular basis (our driver's side stays much cleaner than our passenger sdie mirrors).
Truthfully I think they are sexy as hell, they put an exclamation point at the end of your wash adding sizzle to the steak, and allow people to look at both sides of their vehicle before they exit. I honestly would place their value against any of the on-line extra services you offer.
As for the danger of collision? In this day and age, any exterior only tunnel with no employees at the end, that does not have an anti-collision system in place has already had lots of vehicles bump each other without mirrors.
BTW, we are a 150' front wheel pull conveyor which is the reason for the extra conevyor after the dryers. At the end of the conveyor we also have a large illuminated sign the spells out the word R-E-L-A-X from top to bottom as the come out of the dryers. The two bottom sections of the sign then come on when the vehicle reaches the end and say "Thank You" and "Please Exit" The we also have a sign about 5-6 feet outside the building as the vehicle comes out that says "Put Car In "D" Now and Pull Out." Even with all these signs, the anti-collision still goes off from time to time. That will occur no matter what you do.
Go for it, they are great and your customers will love them, I guarantee it!
