Re: Mix Fleet VRP

John Skoa wrote:
> Hello all
>
> I have a VRP problem where there are multiple type of vehicles (with
> diff capacity, and costs -> fixed & variable) available. Availability
> of vehicles is not a constraint.
>
> There are number of drop points in the space where goods needs to be
> delievered from the depot. There is only unit demand at each of these
> points. Distance, and time to travel between these points are known.
>
> There is restriction that the route should not be beyond a certain
> time limit.
>
> The problem is to determine a good mix of vehicles which one should
> have to minimize the overall cost (both fixed, and variable).
>
> Has this problem been looked at somewhere? Any leads on the problem?
>
> Are there MIP/CP constructs available of such a problem? Even if we
> have an MIP/CP model here, won't solve time be an issue using them in
> case of large size problems? So there will be need of heuristics?

Are you interested from an academic point of view, or do you have a real 
problem to solve? There are a number of commercial packages which 
'solve' problems of this type using heuristics of various kinds.

Mark Thornton

Optrak Distribution Software Ltd.
http://www.optrak.co.uk