This article deals with the vehicle routing problem with time
windows (VRPTW). This problem consists in determining a least-cost
set of trips to serve customers during specific time windows. The
proposed solution method is a memetic algorithm (MA), a genetic
algorithm hybridised with a local search. Contrary to most papers
on the VRPTW, which minimize first the number of vehicles, our
method is also able to minimize the total distance travelled. The
results on 56 classical instances are compared to those of the
best metaheuristics. The efficiency of the MA is similar for the
classical criterion, but it becomes the best algorithm available
for the total distance, being much faster and improving 20
best-known solutions.