SND problems are furthermore partitioned into static and dynamic
problems. While in both groups one determines the frequency
of the service, the capacity allocation, the equipment
planning, and the routing and flow of commodities, in the former
it is assumed that all problem aspects are static over the time horizon,
and in the latter, at least one feature (e.g. demand) varies over
time. Table 2 shows a growing body of literature in SND problems
compared to NFP problems. This trend indicates that decision makers
take the fixed cost of employing services into account and look
for cost-efficient solutions.