Re: Mix Fleet VRP

john,

Please refer a paper by chein et al published in Transportation
Science(1989 vol 23).
Where they tried solving integrated Inventory allocation and routing
problem. Where the cost component has both fixed and variable parts.
 They have tried solving problem using Lagrangian relaxation and used
a heuristic for getting feasible solutions.
I think by adding time window constraints in their model you can also
solve your problem in similar fashion.
They have solved problems up to 30 nodes and quality of solution is
also good.
Thanks,
Sharad Gupta
SUNY-Buffalo



> I am interested from academic point of view, and interested in knowing
> what exactly is available in solving this type of problem.
> 
> Can you direct me to some heuristics/methods where this "mix fleet
> problem" has been looked at? References will also be helpful.
> 
> Thanks, and Regards
> John.
> 
> Mark Thornton <[EMAIL PROTECTED]> wrote in message news:<[EMAIL PROTECTED]>...
> > 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