PTV Group - Logistics Forum

Hi there,

as the tour optimization model seems to be one of the more challenging ones (compared to other PTV APIs such as geocoding) I'd like to provide a special view to the topic which is supposed to help you understanding our model. Therefore I wrote this article about "constraints" in tour optimization. Here we go: usually I define tour optimization as follows from a meta perspective:

• give us a set of orders you'd like to fullfil (aka workload)
• give us a fleet we can utilize for that (aka ressources)
• define the required constraints
• we then let you know "what ressource takes care of which order in what sequence"

And here's the view to the constraints - we offer different categories:

• quantity based :
  • orders may occupy a specific capacity
  • ressources may be able to handle a specific capacity at a time...
• time based
  • opening times at locations (or service start times, to be more precise)
  • drivers availabilities (operating hours)
  • break- and rest rules
• skill / equipment
  • orders may require a specific set of equipment or a drivers skill set
  • ressources may offer a set of equipment or skills
  • An order can only be served by a ressource which offers all required skills/equipment
• Structural dependencies
  • an order may have to be served as first or last stop on a tour
  • an order of a specific category of goods may not be server with another category of goods at the same time
  • a tour may be enforced to be based on a single trip
  • a tour may be served only by a single depot
  • a customer site can only be approached once within a tour plan
• Maximumm values :
  • maximum number of customers per tour
  • maximum driving time, travel time, distance
• Handling of routing restrictions related to underlying distance matrix:
  • approach customer stop in driving direction
  • acceptance of routinhg violations / reachability violations
• level of fixation of an (optional) input plan:
  • orders assigned to a specific vehilce can't be shifted to another vehicle
  • a trip that has been assigned to a vehicle can't be shifted to another vehicle and the inner structure of the trip can't be changed (no additional orders, no change of stop sequence)

Some of these restrictions may have to deal with several of the categories at a time, e.g.

• loading patterns are dealing with quanitities and structure
• maximum travel times belongs to maximum values and time based constraints