Hunsaker and Savelsbergh have proposed an algorithm for testing feasibility of a route in the solution to the dial-a-ride problem. The constraints that are checked are load capacity constraints, time windows, ride time bounds and wait time bounds. The algorithm has linear running time. By virtue of a simple example, we show in this work that their algorithm is incorrect. We also prove that by increasing the time complexity by only a logarithmic factor, a correct algorithm is obtained.