Hrmmm.

The Vehicle Routing Problem considers the delivery of goods to a set of customers using multiple vehicles. The aim is to deliver (or pickup, or pickup and deliver) the goods as efficiently as possible.

In the real world, the routes are always constrained. In the OR literature, some of these constraints have been examined (capacity, time windows, etc). However, the diversity of constraints seen in the real world is truly staggering - vehicles can't fit under eaves, complex 2D and 3D loading constraints, complex work/rest rules, connections to ferry timetables, and (my favourite) the "affairs" constraint that limits which customers a driver can visit depending on whether he is currently having, or has had in the past, an affair with staff at the customer (apparently updated weekly).

- blurb for an upcoming lecture. At least that's one thing I haven't been asked to include in our work so far...