  When delivering items to a set of destinations, one can save time and cost by
passing a subset to a sub-contractor at any point en route. We consider a model
where a set of items are initially loaded in one vehicle and should be
distributed before a given deadline {\Delta}. In addition to travel time and
time for deliveries, we assume that there is a fixed delay for handing over an
item from one vehicle to another.
  We will show that it is easy to decide whether an instance is feasible, i.e.,
whether it is possible to deliver all items before the deadline {\Delta}. We
then consider computing a feasible tour of minimum cost, where we incur a cost
per unit distance traveled by the vehicles, and a setup cost for every used
vehicle. Our problem arises in practical applications and generalizes classical
problems such as shallow-light trees and the bounded-latency problem.
  Our main result is a polynomial-time algorithm that, for any given {\epsilon}
> 0 and any feasible instance, computes a solution that delivers all items
before time (1+ {\epsilon}){\Delta} and has cost O(1 + 1 / {\epsilon}) OPT,
where OPT is the minimum cost of any feasible solution.
  We show that our result is best possible in the sense that any improvement
would lead to progress on 25-year-old questions on shallow-light trees.
