Choose vehicles appropriate to the urban area, passenger demand and operating efficiency.
The bus manufacturing industry provides vehicles of various sizes, starting from mini-buses based on delivery vans up to three-section articulated buses with capacity characteristics similar to tramways. In regional and urban transport in medium-sized and major cities the standard bus with a length of about 12 metres is predominant combined with articulated buses (18 metres) and - to a smaller extent - buses with 15 metre length.
Managers should check carefully which type of vehicle is appropriate for the service intended. Major criteria are
Demand level in relation to the frequency intended,
Structure of the city (road network in areas served, e.g. medieval city centres).
In many medium-sized cities with a considerable demand level, standard buses might fit best.
However, in towns and smaller sized cities (< 50,000 inhabitants) medium-sized buses with a length of about 10 metres, or midibuses, might be more appropriate, because smaller vehicles have a number of advantages:
They are more suitable for narrow streets and / or historical centres.
If they are of the right quality they can be regarded as a marketing element for High Quality Public Transport (HQPT) as they ‘stand out’ from standard buses.
They may fit better to the actual level of demand.
Minibuses may also be appropriate but it is not always economical to achieve a high quality of vehicle with very small buses.
The latter principle (“It is better with smaller buses that operate more often than bigger buses that don’t operate that often”) has to be balanced with the fact that usually the driver accounts for approximately 70 to 80 % of all operating costs. Due to the ability to achieve lower costs by combining orders, resulting in easier maintenance and replacement of vehicles, there is a tendency towards standard buses (12 metres) in smaller cities.
Using too many minibuses can cause problems when demand increases. In some cases it may be appropriate to go for midibuses or even standard buses, because they can also be used on other routes.
Special size vehicles (e.g. double-articulated vehicles, 15m buses, buses with trailers) have special characteristics which can only be really tested in daily operation (e.g. minimum turning curves). It may be advisable to contact other cities to get information about daily operational experiences instead of “re-inventing the wheel”.
If the ticketing system makes this possible, it may be advisable to have two or more doors on the bus. The location of doors in the vehicle and the number of doors per vehicle influence both accessibility while getting on and off the bus, and the accessibility of seats. However, having more than one door may make it more difficult for the driver to control the door operation in a safe way.
When considering the size of vehicles, the maximum capacity of a vehicle (according to technical approval or manufacturer’s declaration) should not be used for calculation purposes, because in daily use the maximum capacity is needed to manage exceptional demand peaks (e.g. during peak hours, on rainy days, or in the case of delays). In Switzerland, Anderhub et al (2008) has shown that a maximum capacity of 3 persons/m2 in dedicated standing areas is accepted by users. Experience shows that about 70% of the maximum capacity can be used for calculations. If demand regularly exceeds capacity, either the frequency of the line has to be adapted or (more likely in small towns) additional services have to be established.
Furthermore, fleet management objectives have to be considered such as:
The vehicle should fit most of the lines and not only just one particular line.
Different sizes and different types of vehicles could increase maintenance expenditures.
Euskirchen (Germany): In Euskirchen, midibuses (10 metres) are in use because these fit better to the actual level of demand. However, replacements will be of the standard bus type (12 metres) due to obtaining lower costs by combining orders.
Firenze (Italy): 4 routes (A, B, C and D) operate in the old city centre using small electric-powered midibuses to avoid pollution and damage to the historic infrastructure. This example is not part of the PROCEED case study analysis.
Lindau (Germany): The urban bus system in Lindau (Lake Constance, Germany) uses medium-sized buses (10 metres) in order to access the historic part of the city centre. Large parts of the city centre are assigned to pedestrian zones; however, the city bus can still enter.
Anderhub, G., R. Dorbritz, U. Weidmann (2008) Leistungsfähigkeitsbestimmung öffentlicher Verkehrssysteme, Schriftsreihe 139, Institute for transport planning and systems (IVT), ETH Zurich, Zurichstudies