OPTIMAL LOCATION OF BUS DEPOTS IN AN URBAN AREA.

Abstract

This paper deals with the so-called plant location and aims to set up a methodology for determining the optimal location and size of bus depots. Location and size of bus depots are usually not efficient, mainly because of: the subsequent growth of the city, or significant changes in location patterns (causing possible inefficiencies in terms of land use); the growing demand for public transport over time (causing ineficiencies in exploiting economies of scale). Nevertheless, any location is usually very difficult to change, due to: the lack of an appropriate methodology to find out better locations; the unpopularity of any decision concerning new locations for bus depots. The poposed methodology aims to investigate the overall costs connected with depots (land use costs + operational costs + journey-to-depot costs) and to minimize them by determining the optimal combination of number, size and location of depots, given the urban transportation network and the overall number of buses. A case study is then developed for the city of Genoa. The present scenario is analyzed with respect to several decision constraints, (geography, feasible depot sizes, resource allocation, bus types, time of investment and budget restrictions). Then, the shortest path between any pair of possible bus stops is computed together with the average number of trips for each bus line and the location, handling and managing costs for each depot. Finally. a Mixed Integer Programming (MIP) model is derived for solving the problem on the basis of the average daily traffic data in the city of Genoa. The model is solved using an optimization software library on a personal computer. 1 Purpose of the paper This papers aims to point out a methodology for optimizing size and location of bus depots in an urban transit company. Sizes and locations of bus depots are often a result of choices taken in the past, no longer efficient with respect to the present technological and market conditions. For example, after a significant urban growth the depot location Transactions on the Built Environment vol 30, © 1997 WIT Press, www.witpress.com, ISSN 1743-3509