“…Numerous scholars, including Newell (1979) and Baaj and Mahmassani (1991), have pointed out that traditional mathematical programming has difficulties in generating an optimal transit network due to nonlinearity and nonconvexity of the model, combinatorial explosion, multiobjective nature, and spatial layout of routes. With the improvement of search algorithms and computer technology, important heuristic research has been done (Hasselström 1981;Baaj and Mahmassani 1991;Shih, Mahmassani, and Baaj 1998;Ceder and Israeli 1998;Pattnaik, Mohan, and Tom 1998;Chien, Yang, and Hou 2001). All of these studies are based on the combinatorial search approach.…”