The vehicle routing problems presented so far have presented an ideal situation: continuous availability of vehicles. However, in real-world problems, the people driving these vehicles need to occasionally interrupt the trips. These interruptions might include coffee and lunch breaks, and if the trips are longer than one working day, overnight breaks. In Dispatcher, these interruptions are modeled as vehicle breaks.

A vehicle break is performed by a vehicle on a particular dimension (usually time), has bounds for the start time, and possibly a variable duration with bounds as well. Breaks can interrupt visits or not, but by default visits are unbreakable. Note that breaks themselves cannot be interrupted.

Breaks are created as constraints on vehicles. More than one break can be specified per vehicle, and breaks can be involved in metaconstraints. Constraints can be applied across a number of breaks to ensure that drivers take an appropriate amount of time off.

The problem considered in this lesson is a PDP problem. Pickups and deliveries are considered over a five-day period, with vehicle breaks taken each day for morning and afternoon coffee, and lunch. Overnight rest periods are modeled as breaks with a minimal number of rest hours to take between two consecutive night breaks.

The first step is to write a natural language description of the problem. A good way to start this process is to analyze the variables and objectives.

What are the constraints in this problem?

The objective is to minimize the cost of the delivery of all the parcels, while meeting all the break requirements.