Introduction

With the increase of the living standards in Istanbul, the population is asking for a higher service and quality. This requirement is also including the quality of the public transportation system. Istanbul Electricity, Tramway and Tunnel (IETT) General Management, which carries a huge part of the passenger density as a public transportation corporation, is the most important actor in Istanbul traffic. Serving in high quality is very difficult in Istanbul, when the constraints are considered, like road conditions, number of vehicles, and high density of the passengers especially in the peak hours. The number of the buses is increasing day by day in proportion to the population of the city. Besides, this increase brings extra problems caused by the ages of the buses, accidents in the traffic, lack of the road infrastructures, and overusing the buses. Maintenance activities, especially, have a vital importance on journeys to eliminate these problems and to ensure customer satisfaction without failures.

The difficulties in Istanbul for effective public transportation are rapid and unplanned public development, historical settlement texture, population, rapid increase in vehicle and transportation requirements, and geographical features (rough topography, Bosphorus and The Golden Horn). As an indicator, there are 13,532,745 average passengers in public transportation system of Istanbul and 2,039,837 of them use IETT. This is a very high number when it is compared with the world average. IETT carries passengers with a 334 bus fleet in bus rapid transit (BRT) system and with 2,279 buses in other lines.

In bus garages, the repair and maintenance activities and corrective and preventive actions are done. There are nine garages in IETT and the number of busses and the spaces are shown in Table 1.

Table 1 Specifications of garages.

Garage Number of buses per garage Total space (m2) Indoor space (m2)
İkitelli 528 192,000 28,000
Anadolu 404 58,200 10,000
Topkapı 125 17,588 7,100
Edirnekapı 400 60,000 6,720
Ayazağa 314 102,275 11,500
Hasanpaşa 368 37,000 4,000
Kağıthane 220 65,000 7,920
Beykoz Şahinkaya 147 13,000 2,300
Sarıgazi 137 15,000 1,420
Total 2,619 560,063 78,960

As a result of the traffic congestion and the number of travels in a day, lots of breakdowns and the maintenance requirements occur and the failure frequency increases in Istanbul. The maintained bus numbers per day within IETT are shown in Table 2.

Table 2 Maintained bus number per day.
Year Maintained bus number
(daily average)
2011 33
2010 35
2009 35
2008 37
2007 47
 * The data has been collected from the annual reports that are published on IETT website.

In this study, we try to determine the best locations for bus garages to operate the maintenance and repair activities. There are many important criteria that affect the location decisions, like cost, time, infrastructure, environment, accessibility, other macro factors, and so forth. Istanbul is a growing city and the land use is very important in terms of the city master plans. Therefore, probable places for bus garages are determined by the IETT authorities and best alternative is selected considering the above-mentioned criteria. These criteria are constituted considering EN 13816 standards which try to promote a quality transport operations and focus interest on customers’ needs and expectations.

An integrated MCDM technique, fuzzy AHP and fuzzy AD, is used for this purpose. Fuzzy AHP is used to weight the criteria according to the precise and imprecise judgments of the decision makers. Then the obtained weights of the criteria are utilized as an input data in fuzzy AD to determine the precedencies of the alternative locations.