A public transport system must accommodate a very large number of individual trips. It’s not possible to provide direct public transport routes to meet all requirements But it’s possible to go a long way towards achieving this by providing a network of routes , so that passengers can make complex journeys by using a combination of routes.
Many transport systems consist of routes planned in isolation rather than as parts of coordinated networks. This is usually unsatisfactory for meeting the requirements of a significant proportion of travelers. Poor route planning may result in poor route coverage, an excessive requirement for interchange between routes, and irregular frequencies.
Others route networks have been designed to provide convenient links between all points where there is demand. Some have been designed to meet predetermined standards or criteria such as a maximum number of interchanges between routes on any journey.
Route planning always lags changes in demand
In theory, market forces will eventually lead to an optimal transport system. But in practice this evolution, which effectively is by trial and error, would take considerable time. And since cities are constantly growing and changing, the ideal route pattern will never evolve.
Indeed, even with a sophisticated planning capability, development of transport services will always tend to lag behind changes in demand. Transport planning in cities in developing countries is especially difficult, because of the rapid pace of change. Plans must be kept under regular review, and revised as necessary.
Public transport planning may be based on transport demand and supply data, derived from operators’ own internal systems, and from surveys. Other planning data available to transport authorities may include overall transport plans and projections, land use plans, plans for private and public sector developments, traffic demand forecasts, and economic forecasts.
Regular route revisions are necessary
In some cities route revisions are carried out regularly as a matter of routine. But in other cities there have been virtually no changes for many years despite the city growing and changing considerably.
For example in Kingston, Jamaica, a new central business district, New Kingston, was developed about eight kilometers from the original central area. For several years there was very little change to the network of bus routes, which was still focused on the original central area. Commuters traveling to New Kingston had to change buses during the course of their journeys.
Alternative Approaches to Network Design
There are many ways of configuring a route network to meet passengers’ requirements, each has advantages and disadvantages — what is appropriate in one city may be unsuitable in another.
A route network may be designed to be operated on a fully commercial basis, with every route producing a profit, or there may be social objectives, requiring the provision of some unprofitable routes. The structure of the system, the degree of regulation and competition, and the extent to which regulations are complied with, will influence the type of route network that is most appropriate.
Walking distances and route frequency
In most cities, the main public transport corridors radiate outwards from the central area, with routes branching from these corridors to serve points on either side. The number of these branches will be partly influenced by the nature of the road system, and by policy and market forces. If people are not prepared to walk long distances, bus routes will need to penetrate further into residential areas than otherwise.
Similarly, if there are parallel roads along a corridor, a decision must be made whether or not to concentrate all routes along one road, or to split them between the two roads. The first alternative will give a higher frequency of service, and therefore less passenger waiting time. But it could mean greater average walking distance, and perhaps increased traffic congestion. The second will give lower frequency, and longer average waiting times, but shorter average walking distances.
Converging routes on a single focal point
In a city with a population of approximately 1 million or more the central area will normally cover a large area so that passengers’ destinations are widely dispersed. Where the distances between these exceed acceptable walking distances, it is inappropriate for all routes to converge at a single focal point. There may therefore be several points, each constituting the focus of a number of radial routes, and possibly requiring another sub-network of routes connecting them.
This will also apply in a conurbation comprising two or more contiguous cities, each with its own distinct centre.
Terminating in the city centre
An important choice is whether routes should terminate in the city centre, or continue across the central area to points on the opposite side of the city. Where most passengers travel to and from the city centre, and rarely travel between one outer suburb and another, the decision as to whether routes should terminate in the city centre or not is a purely operational one.
Disadvantages of routes terminating in city centers include:
- Buses can cause congestion while standing between journeys and when turning.
- Valuable land is often occupied with bus terminal facilities.
- Time is wasted by buses turning round (reducing bus utilization and increasing costs).
- Passengers wishing to travel across the city centre will have to change buses or walk for part of their journeys.
Advantages of routes terminating in city centers include:
- Schedules are less likely to be disrupted by congestion (since there can be provision for recovery time in the city center).
- Convenient interchange between routes may be provided at a common terminal.
- Fare structures are less complex.
On balance, the advantages of operating routes across the city centre usually outweigh the disadvantages, though each case must be assessed on its own merits.
Non-radial passenger trips can be handled in various ways. In a large city, it is often appropriate to operate a number of routes linking various suburbs, and not reaching the city centre, perhaps including circular routes linking outer points. Often these are operated by smaller vehicles than those used on routes serving the city centre. Sometimes inter-suburban movement can be catered for by extensions or diversions from the main radial routes.
A transport network may include a number of feeder bus routes, which feed passengers into trunk bus routes and to rail lines. These offer an alternative to operating a large number of different routes along a common corridor, each branching off to serve points off the main route.
Through bus services should normally be operated where demand from the outlying points is sufficient to justify them, but where demand is low, it is often more economic to operate feeder services, using smaller vehicles. Also, where road conditions prevent the use of larger vehicles over part of a route, it is usually preferable to operate small vehicles on this section, feeding into a service using larger buses for the main section. This eliminates the need for small buses operating alongside larger buses on main urban routes.
Hub-and-spoke route systems
In certain circumstances, particularly in smaller towns, a hub-and-spoke route system may be appropriate. This means all routes meet at a central focal point, and passengers are able to travel between any two points in the city by transferring from one route to another. Where journey times are relatively short, and service frequencies are high so that transfer times are minimized, such a system may be acceptable. But in general, particularly for regular commuter traffic and where traffic congestion is a problem, a high proportion of indirect journeys is unacceptable.
Types of routes
The bus routes themselves may take various forms. The basic and most common type of route is the end-to-end route, which operates between two points, following the same roads in both directions, except where one-way street systems necessitate minor deviations. Alternatively, a route may be circular, returning to the point of origin without traversing the same roads twice. Circular routes are often found in suburban areas, sometimes circling an entire city. Inner-circle routes around city center areas are also common.
Another option is a route combining straight and circular sections. At the end of the route the bus, instead of turning and returning by the inward route, operates in a loop. It rejoins the inward route after completing the loop, stopping in the central area for no longer than is required to set down and pick up passengers.
Such an arrangement can be particularly effective for a central business district as an alternative to operating across the city center. It can provide better service coverage than a terminal operation since passengers are able both to join and leave the bus throughout the circuit. This enables buses to serve a wider area than would otherwise be the case, and eliminates the need for city-centre terminal or turning facilities. Loops are also common at the suburban ends of routes, where buses operate in a circuit around a residential area to provide better coverage.
Another variation of the straight route is one that forks near one or both ends to serve different terminal points. These are sometimes regarded as separate routes, even though they operate in common for most of their length. Some routes may be dumbbell shaped, with a loop at each end. These are normally found where buses operate across the city center from one suburb to another, and operate in a loop around the residential areas at the outer ends.
A route network may comprise routes of several or all of these types.
Routes and artificial boundaries
Some networks suffer from artificial boundaries which bus routes do not cross. For example in Beijing, there are several points on the outskirts of the central area where inner and outer bus routes meet. Through passengers must transfer between vehicles. In Indonesia the manner in which public transport services are regulated results in a similar situation at city boundaries. Although convenient interchanges are often provided, the need to change vehicles increases journey times for passengers, and the additional turn-round times reduce vehicle utilization.