Decide your planning task based on the objectives for Public Transport in your city / town. Plan your system to be simple, attractive to users and efficient.
The major principles of high-quality urban bus planning in small and medium-sized towns can be summarised in the slogan “Think tram, use bus!” While the tram’s tracks always serve as the backbone of such a network, this feature is often missing in urban public transport systems which rely exclusively on buses. The network should have simple, attractive core lines.
User requirements of urban bus system users may be different, e.g. shoppers aim for a direct access to the shopping area (e.g. city centre pedestrian zone) while commuters aim for fast connections to the central business district or industrial areas of the town. Since ‘collective transportation’ of persons with different requirements is a main principle of public transport, the design of the network structure has to make selective choices and to solve important dilemmas. There are few simple and general answers.
If an existing network is being improved it is often fruitful to start the network planning process with an analysis of the strength and weaknesses of the existing network, thus defining challenges for network improvements. In this analysis it is useful to think of the various groups of customers that might use the system for different travel destinations and purposes (see guideline 1.2 User needs and expectations). The planners should also consider the network from a practical operational point of view.
The following work structure can be used to define the main network that is being aimed for in the long term:
Try to cover the origin-demand links with as few high frequency lines as possible, creating cross-city lines between corridors on each side of the city centre (trunk line network).
Look for suitable tangential lines or corridors that work together with the radial lines to form a more complete network.
Consider regional services as well, so as to be able to create an integrated city / regional network with smooth interchanges for users.
Study how access to the trunk line network can be improved; through bus service improvements, the provision of high quality stops and interchanges, and priority for bus services in interchanges.
For more information on available line types see ► Background information: Common line types in urban bus networks.
Further network performance criteria to take into consideration are:
Distance between stops: A longer distance between the stops makes the line faster but the accessibility lower. The distance between the stops is always determined by the respective land use in relation to the average walking distance of passengers to the stop. The distance between stops has to be adjusted with regard to travel speed and travel demand at different destinations and is usually at an average of about 400m in urban networks.
Walking distance: A longer walking distance makes it possible to have longer distances between the lines, which gives the lines a wider catchment area and the possibility of having a higher frequency. But the average walking distance cannot be too long if the bus system is to be accessible. An average walking distance of less than 600 metres (400 m as the crow flies) is considered good.
Routing of the lines: The lines should pass through both the central and residential areas, not around or along one side of the area. The lines should also be as short and direct as possible. Note that these two aims are often in conflict so careful planning is needed to achieve an acceptable compromise.
Hierarchy of Public Transport networks: The trunk line network is usually at the top of the hierarchy. Below this there are the tangential lines and other complementary lines (e.g. connecting business parks to the city centre) where the traffic demand is not that heavy. At the last level, there can be a service network designed to cover the special needs of the elderly and disabled (widespread in some countries, e.g. Finland and Sweden), an additional network for school services (widespread in some countries, e.g. Germany, France), or demand-responsive or flexible services for outlying areas of light population density or low usage.
Network planning in smaller cities: Especially for small cities the efficient use of a limited number of vehicles is a key issue in order to keep the costs of the service at an acceptable level. Hence, the length of the line (and the necessary running time) should always be in line with the circulation time of the vehicle, i.e. the vehicle should be back at the terminus within the fixed frequency interval. If this cannot be the case, the line would need to be accelerated because the operation of an additional vehicle would make the service somewhat inefficient.
Synergy with regional bus services: Selected complementary lines of the urban bus network (apart from trunk lines) may be served by joint operation and co-ordinated timetables of regional buses and urban buses. This can avoid ineffective parallel services and contributes to a better use of available resources. However, there are certain prerequisites for such an approach. In addition to similar service characteristics (comparable quality standards of vehicles, low likelihood of delays), a full tariff integration between urban bus services and the regional lines is necessary. Furthermore, the integration of local and regional services should not be in conflict, e.g. an unreasonable lengthening of travel times for regional passengers should be avoided.
The relationship between trunk line corridors and feeder lines from smaller communities will also impact the network planning. There are at least two different techniques for servicing trunk line and feeder line areas: the “Trunk-Feeder technique” and the “Convoy technique”. With the Trunk-Feeder technique, larger buses serve the principal corridors. At the end of these corridors (and / or along them) an integrated terminal station is placed to allow efficient transfer to smaller feeder buses that continue into smaller communities. The Convoy technique does not necessitate the need for transfer at terminal stations: instead a convoy of buses with different ultimate routes all ply the same main line corridor. At a certain point, each of these buses leaves the main corridor and continues onto individual routes.
Serving the needs of all passengers in the same system may result in the compromise of a network that does not meet all special needs of passengers and at the same time is not attractive to the majority of potential passengers. For example, it is difficult to fulfil the different needs of disabled persons in a regular network system or to offer direct services from home to school for pupils. Consequently, options to offer special services could be considered.
Almere (The Netherlands): The public transport network of Almere has a fairly dispersed grid (the average distance between the bus routes is about 800 metres, the average distance between the bus stops is 600 metres) oriented at the city centre / central station and where possible on one or two other railway stations / district centres. The lines are as much as possible cross-city (from one district via the City Centre / Central Station to another district).
Aalborg (Denmark): The public transport network of Aalborg (Denmark) is quite finely-meshed and most lines are oriented at the City Centre and the Central Station. The lines are as much as possible cross-city (from one district via the City Centre and the Central Station to another district). The metro bus lines are the backbone of the system and are characterised by a high speed obtained through priority at all intersections and by high frequency. The metro bus lines cover 50% of the dwellings and 60% of the workplaces in the city.
Cherbourg (France): The urban bus network in this urban area of 94,000 inhabitants on the Normandy coast was completely restructured in September 2008. The new network, strongly marketed under the name “Zéphir” is structured around two trunk bus routes called “Métronomes” with an 8 minute frequency on one and a 10 minute frequency on the other throughout the day, including Saturdays. Five additional main bus services in the second level of hierarchy have a clock-face timetable of every 15, 20 or 30 minutes dependent on the bus line. This is complemented by the “Domino” network which serves school traffic at specific times, and the “Itinéo” network which serves less dense outlying areas (generally with scheduled services in peak hours and a demand-responsive service requiring a reservation at other times). With the new network, 90% of the population is now within 300 metres of a bus stop, and the operator aims to increase bus use by 20% in the next five years (2008 to 2013).
Gävle (Sweden): The main network of Gävle consists of 3 rapid bus lines and 3 "local" lines. All lines are cross-city lines (from one district via the City Centre / Central Station to another district). The rapid bus lines are arranged in a dispersed grid pattern, while the local lines cover areas between the rapid lines and smaller districts, sometimes going along the same streets as the rapid bus lines. In addition to the main network there is a range of additional lines.
Lemgo (Germany): The urban bus network in the city of Lemgo (42,000 inhabitants with approx. 32,000 within the catchment area of the urban bus system) has 3 cross-city and 2 radial lines (8 radial line sections) and provides an example of an urban bus system in a smaller city. All lines are connected at the central stop ‘Treffpunkt’ (‘meeting point’) at the same time (‘Rendezvous’ of buses) in the core of the city. 7 of the 8 line sections have a standard headway of 30 minutes corresponding with a travel time of 30 minutes (round trip). The number of necessary vehicles per branch is minimised at exactly one vehicle. The 3 cross-city lines have additional runs (every 15 minutes) during peak-hours.
Münster (Germany): Münster’s bus line 22 provides an example of synergies with regional bus services. The line runs in a regular 20 minutes interval to a suburb with partly rural characteristics. The service is fully integrated into the urban bus network; however, only one bus per hour is an urban bus services – the two other runs per hour are actually regional bus services continuing to 2 different destinations in the region. The applied tariff is fully integrated and the service quality between both operators is comparable. Münster has about 270,000 inhabitants.
Rheine (Germany): 10 of the 12 radial lines have a headway of 30 minutes and the circulation time between the ‘Bustreff’ central bus stop and the terminus exactly fits into this pattern: The same bus is back at ‘Bustreff’ 30 minutes later, resulting in a demand for 1 bus per radial line.
Sint-Niklaas (Belgium): The bus corridor that crosses the city centre is not only served by urban buses, but by regional buses as well. This intensifies the service on the bus corridor to a high-frequency service (every 7 minutes).
Cross-city line: Line between two terminuses (e.g. suburbs or sub-centres) crossing the city centre. Very often used in urban bus planning, especially with trunk lines.
→ Advantages: Availability of additional direct connections without changing vehicles. No waiting time of vehicles in the city centre (which would create a loss of space by parking buses in the core of the city)
→ Limitations: Not always possible to create reasonable cross-city lines. Increased risk of delays.
Radial line: Line between one terminus (e.g. a suburb or sub-centres) and the city centre. Often used in urban bus planning especially with trunk lines.
→ Advantages: Limited risk of delays.
→ Limitations: Requires changing vehicles to provide additional connections. Results in waiting time of vehicles in the city centre (and therefore losing space by parking buses in the core of the city).
Loop line: Cross-city or radial line with a short loop at the end of the line. Often used in smaller cities.
→ Advantages: Very high coverage of the catchment area (e.g. residential area) at the end of the line.
→ Limitations: There is no real terminus; vehicles need to run the loop without any waiting time.
Ring lines: Line departing and ending at the city centre serving a circle in both directions, often only as a one-way service. This is sometimes used to integrate low-density areas of a city into the urban network or during evening hours and for provision of night buses.
→ Advantages: High coverage of the catchment area of the line with a limited amount of runs.
→ Limitations: Network structure is not easy to understand. With a one-way service there is also a high travel time for passengers joining the vehicle at the first stops of the line.
Tangential lines: Line between two termini (e.g. a suburb or sub-centres) without crossing the city centre. This sometimes used to create fast direct connections between major sub-centres, especially in bigger cities.
→ Advantages: Fast connections between sub-centres.
→ Limitations: Demand level of tangential lines often remains below expectation (the city centre, a major trip destination in urban bus networks, is not served).