We propose an incremental algorithm for the problem of maintaining systems of difference constraints. As a difference from the unidirectional approach of Ramalingam et al., it employs bidirectional search, which is similar to that of Alpern et al., and has a bounded runtime complexity in the worst case in terms of the size of changes. The major challenge is how to update the solution efficiently after the bidirectional search discovers a region that needs changes. Experimental results show that our approach is much faster in runtime and generates much smaller changes than the algorithm in Ramalingam et al. We also perform an experimental study on the edge value heuristic Alpern et al. and results show that a simpler method may be faster in practice.