In conflict-free routing a set of agents have to traverse a common infrastructure without interfering with each other. Maza and Castagna [1] showed how route plans can be repaired by maintaining the priority of agents on infrastructure resources. They also developed an algorithm that allows agents to change priorities to avoid long waits. We extend the work of Maza and Castagna by (i) specifying an algorithm that allows more priority changes, and by (ii) defining a graph structure that can predict exactly which priority changes will lead to a deadlock, and which will not. Our experiments show that our algorithm performs around twice as many priority changes as Maza and Castagna's algorithm. Also, the average delay produced by our algorithm is lower in our experiments, although there is no clear relation between the number of priority changes and the delay: priority changes seem the most effective when the system is not fully congested, and when there are few incidents that cause d...