Every one relies on some kind of transportation system nearly every day. Go ing to work, shopping, dropping children at school and many other cultural or social activities imply leaving home, and using some form of transportation, which we expect tobe eflicient and reliable. Of course, efliciency and reliabil ity do not occur by chance, but require careful and often relatively complex planning by transportation system managers, both in the public and private sectors. It has long been recognized that mathematics, and, more specifically, op erations research is an important tool of this...