Urban freight distribution/delivery usually leads to traffic
congestion, safety concerns, air pollution, and high logistic
costs [1]. In recent years, more and more carriers and shippers
have recognized the importance of designing efficient distribution
strategies to improve the level of customers service
and reduce the financial and environmental cost of freight
transportation [2]. However, the extensive literature on the
classical vehicle routing problem (VRP) and its variants
have primarily considered the problem using static traffic
information with corresponding constant travel times. In
recent years, a number of studies take account of substantial
variation in speeds and improve the model by taking the time
dependency of travel times into consideration (see details
in Section 2). However, in urban transportation system, lots
of random factors, such as uncertain traffic volume, severe
weather conditions, and incidents, can lead to the uncertainty
of travel times during most of the day, especially during
the morning and evening peak periods. Those nonrecurrent
events can significantly affect the reliability of the
transportation system and contribute to a stochastic timedependent
(STD) congested transportation network. Urban
route designs that ignore these significant variations and
uncertainties of travel times are often found to be inefficient
within a congested traffic condition and may contribute to
higher operational costs or inferior customer service [1].
Therefore, in order to optimize the freight distribution
performance in urban settings, both the random and timevarying
properties of the link travel times must be considered.
In this paper, we refer to the stochastic time-dependent VRP
with hard time window (STDVRPTW). The aim of this study
is to devise good and computationally efficient approaches to
assist the fleet dispatchers operating in an urban congested
environment. To utilize available resources for serve timesensitive
customers, this paper takes into consideration of
Hindawi Publishing Corporation
Discrete Dynamics in Nature and Society
Volume 2015, Article ID 914309, 10 pages
http://dx.doi.org/10.1155/2015/914309
2 Discrete Dynamics in Nature and Society
the following travel-time properties:(1)for certain routes, the
travel times vary according to the time of day; (2) the travel
time is stochastic