Contents I. Introduction
Nowadays, transportation and distribution companies face ever increasing pressures to operate more efficiently to reduce the fuel consumption. Such pressures are fuelled by many sides of reasons. The first is the surging fuel costs. Fuel cost accounts for a large and increasing part of transportation costs. According to [1], for a long-haul fully loaded truck with a capacity of 20 tons, fuel consumption accounts for as much as 60% of the operating cost. It is reported that for road transportation company in Shanghai, China, its fuel cost accounts for 67.41 % of the total transportation cost. Therefore, numerous carriers in China are struggling to save fuels consumption so as to reduce their operation costs. The second reason is the raising pressure of saving energy consumption to reduce automobile exhaust and greenhouse gas emissions. Statistics show that transportation accounts for 20% of the world's energy consumption, and becomes one of the most important sources of haze and greenhouse gas emissions. In US the percentage of total greenhouse gas emissions from transportation sector rose from 24.9% to 27.3% between 1990 and 2005 [2]. More and more countries regard transportation as an important opportunity in goal of reducing energy consumption and greenhouse effect, and consequently charge higher prices for fossil fuel.
