All depends on what problem you are trying to solve. IMO, the problem is "how do we allocate road so that high utility use gets precedent over low value use, w

All depends on what problem you are trying to solve. IMO, the problem is "how do we allocate road so that high utility use gets precedent over low value use, without defining high/low value as 'rich/poor person wants to get from a to b'" Expiring credits is an idea, as are a lot of options. Designed markets are a devil-in-the-detail endevours. A market is a good tool for this job, that's why economists and wonks like tolls. But, not every market needs to be the market. In this case, The Market is probably worse than the no market free-for-all.