# Introducing slack or wait time into passenger routing problem using VRP

1887
2
10-20-2010 04:50 AM
by
New Contributor
I am trying to schedule transportation for passengers to appointments at a facility.  I am having problems controlling the wait time on the resulting route effectively.  My test problem consists of 3 passengers located at various locations within 10 minutes of the single facility.  One of the passengers has a 7:00 am appointment and the other two have a 10:00 appointment.  I constructed the problem with six total orders and three order pairs as follows:

Orders:
Passenger 1 - pickup quanity 1 located within 10 minutes of facility, service time .5
Passenger 2 - pickup quanity 1 located within 10 minutes of facility, service time .5
Passenger 3 - pickup quanity 1 located within 10 minutes of facility, service time .5
Facility 1 - delivery quanity 1, TimeWindowStart1 = 7:00, TimeWindowEnd1 = 7:05, service time .1
Facility 2 - delivery quanity 1, TimeWindowStart1 = 10:00, TimeWindowEnd1 = 10:05, service time .1
Facility 3 - delivery quanity 1, TimeWindowStart1 = 10:00, TimeWindowEnd1 = 10:05, service time .1

Order Pairs:
Passenger 1,Facility 1, MaxTransitTime = 60
Passenger 2,Facility 2, MaxTransitTime = 60
Passenger 3,Facility 3, MaxTransitTime = 60

I have also included a depot and a single route.

When I solve this problem, Passenger 1 and Facility 1 are unassigned.  The route created is:
Passenger 2 - Arrive at: 9:46
Passenger 3 - Arrive at 9:56
Facility 2 - Arrive at 10:04
Facility 3 - Arrive at 10:05

If I increase the MaxTransitTime in the order pairs to 240, the problem will solve with the resulting solution:

Passenger 1 - Arrive at: 6:51 - Depart at 6:51
Facility 1 - Arrive at 7:05 - Depart at 7:05
Passenger 2 - Arrive at 7:16 - Depart at 7:17
Passenger 3 - Arrive at 7:27 - Depart at 7:27
Facility 2 - Arrive at 7:35 - Depart at 10:00 - Wait time 145
Facility 3 - Arrive at 10:00 - Depart at 10:00

I need to control the location of the wait time.  It is obvious that my original set of constraints can easily be met if there is a mechanism to ask the vehicle to wait between Facility 1 and Passenger 2.  How can I accomplish this?  Am I missing some type of configuration that allows slack or wait time?
Tags (2)
2 Replies
by
Occasional Contributor
Hi,

You need to add the pickup time window to avoid the wait time between Facility 2 and Facility 3. VRP solver will only apply the wait time in front of the orders with time windows. You may try to add the pickup time window for passenger 2 and 3 (i.e. [9am, 10am]) and see whether the solution meets your expectation.

Please let me know if you have more questions.

Thanks.

Anna
by
New Contributor
Thank you Anna, your solution worked well for me.