A new consistent vehicle routing problem for the transportation of people with disabilities

Abstract

International audiencen this article, we address a problem of the transportation of people with disabilities where customers are served on an almost daily basis and expect some consistency in the service. We introduce an original model for the time-consistency of the service, based on so-called time-classes. We then define a new multiday vehicle routing problem (VRP) that we call the Time-Consistent VRP. We address the solution of this new problem with a large neighborhood search heuristic. Each iteration of the heuristic requires solving a complex VRP with multiple time windows and no waiting time which we tackle with a heuristic branch-and-price method. Computational tests are conducted on benchmark sets and modified real-life instances. Results demonstrate the efficiency of the method and highlight the impact of time-consistency on travel costs. © 2014 Wiley Periodicals, Inc. NETWORKS, Vol. 63(3), 211-224 201

The Generalized Consistent Vehicle Routing Problem

“…In the ConVRP, Feillet et al (2014) demonstrate cost savings of up to 7.5% if driver consistency is relaxed. In the (2013) studies the driver assignment vehicle routing problem; the increase in cost decreases from 12% to 2.9% if a strict driver consistency is enforced only for 75% of the customers.…”

“…In Feillet et al (2014) and Groër, Golden, and Wasil (2009), drivers have to start their route at time 0. With this restriction, the reported cost of improving arrival time consistency is 5.9% in Feillet et al and between 6.6% and 15% in Groër, Golden, and Wasil.…”

“…An alternative approach to model time consistency is presented in Feillet et al (2014). In contrast to the ConVRP, where the maximum arrival time difference of each customer is bounded, the authors minimize the maximum number of time classes in which a customer is visited.…”

The multi-objective generalized consistent vehicle routing problem

“…Compared to the minimal cost routing plan, the maximum arrival time difference can be reduced by 50 percent at the cost of 1.58 percent longer travel time, on average; improving arrival time consistency by 70 percent costs 3.84 percent. Feillet et al (2014) report 5.9 percent higher routing cost when arrival time consistency is considered; the increase in Groër et al (2009) is between 6.6 percent and 15 percent (the results in Groër et al (2009) also include the cost of perfect driver consistency.) The vehicle departure time from the depot is fixed in Feillet et al (2014) and Groër et al (2009); with this restriction, a 60 percent tighter constraint on l max increases cost by up to 186.15 percent if departure times from the depot are fixed (Kovacs et al (2014c)).…”

“…Feillet et al (2014) report 5.9 percent higher routing cost when arrival time consistency is considered; the increase in Groër et al (2009) is between 6.6 percent and 15 percent (the results in Groër et al (2009) also include the cost of perfect driver consistency.) The vehicle departure time from the depot is fixed in Feillet et al (2014) and Groër et al (2009); with this restriction, a 60 percent tighter constraint on l max increases cost by up to 186.15 percent if departure times from the depot are fixed (Kovacs et al (2014c)). High levels of time consistency can be provided with small increases in travel cost when departure times are flexible (Kovacs et al, 2014a(Kovacs et al, , 2014c.…”