The final topic in this chapter is known as Arc Routing. This is the term used to apply to a family of problems in which all links within a defined service area must be visited. It is thus a specialized routing problem.
Common variants of the problem include: those in which not all links need to be traversed; cases where some or all links are directed; cases in which links have variable traversal costs depending on direction; cases where the links and/or vehicles have capacity constraints; cases where demand varies along the links or between links; and hierarchical problems, in which one set of edges must be served before another. A thorough review and explanation of arc routing problems and their solution may be found in Moshe et al. (2000).