Now and then a transit agency tries some kind of "on time or we pay" guarantee. In the Montréal suburb of Laval, for example, the buses are equipped with Global Positioning System (GPS) technology, and the deal is that if your bus is more than five minutes late (a fact that the agency can verify via GPS), you can demand a free bus ticket, which is nice but not much of an incentive for the agency. It seems to me the same GPS-driven approach could be used to implement a policy if "when we're more than x minutes late, we stop collecting fares." That would actually help a late bus get back on time, because fare transactions are so time consuming.
There are excellent reasons not to do this, of course, or to do something more subtle. For one thing, lateness has so many causes beyond the agency's control that it could cause substantial unavoidable payouts that would ultimately come at the cost of service.
For very frequent urban routes, a better GPS-driven scheme would be based on actual headway (time between consecutive trips, i.e. maximum wait time) rather than timetable, for reasons I discussed here. You could stop collecting fares on any bus that is more than __ minutes behind the one ahead of it. I'd suggest x be something like 3 times the published headway or ten minutes, whichever is less.
Still, we'd have to remember that the lost revenue, if substantial, would come out of service, sooner or later.
I'm curious if any readers have encountered an effective one. By effective I mean one that actually helps motivate good system performance, rather than just shifting scarce funds from service into claims.