Principle 4: Simplicity

Concentration of public transport resources is fundamental to maintain the integrity of a frequent network core. To promote long-term public transport-supportive ridership and land uses, two or more parallel routes that are infrequent have to be streamlined into one single frequent route. Bus route fixity problem is a major challenge, and cross-agency implementation is required to fix bus and pedestrian routing permeability.


One section one line principle eliminates inefficiency

Special caveat to this rule: Network redundancy (refer to the left part of the above diagram) can work well in very high frequency Rapid Transit systems such as New York City Subway and Bogota’s Transmilenio BRT system, simply because the lines that form those systems can afford to be redundant as they already offer a timetable-free headway. These systems typically feature trunk lines that feed into each other, particularly as the lines merge in the urban core area.

  • Many lines that form the New York City Subway are quadrupled, providing multitude of express-local and merge-split network configurations.
    • Redundancy within the antiquated network is often tolerated to afford network reshuffling during regular track and tunnel repair shutdowns, but due to constrained resources (i.e. train breakdowns, reliability issues) there has been effort to simplify the service network as delays on one line can propagate to nearly the entire system
  • Permutation of trunk route segment combination, and local-express combination options resulting in 100+ trunk routes for Bogota’s Transmilenio BRT system
    • BRT buses stick to running within the right-of-way lanes, and trunk-to-local connections at many BRT stations mean congestion faced by local buses in the outskirt has no impact on the reliability of the closed BRT system


Through-routing or pendulum line is an approach of ‘stitching’ multiple short routes into one continuous route. This is an effective way to eliminate unproductive vehicle idling and congestion in urban centers, and increase travel time competitiveness for commuters who need to travel across one or more terminus point.


Through-routing stitches stubs of short ‘feeder’ lines into a long strand of continuous ‘trunk’ route

Types of Route

A route should have a label or name, and services on the route service should follow the same alignment and stop pattern.

Regular Route: Fixed bidirectional route, stops, schedule

Required for frequent network core routes.


Regular route

Express Route: Route with limited stops

Recommended to complement existing very high frequency routes.


Express route

Long and Short-Turn Routes: A set of uniformly-numbered routes with varying lengths and frequency segments

Recommended for segments with gradual change in frequency requirement.


Long and Short-Turn routes

Main and Detour Routes: A set of routes with one main route and one or more detour routes

Recommended for extending coverage to adjacent low ridership areas without impacting linearity of main alignment.


Main and Detour routes

Transfer vs direct service

A spur (or branch) line eliminates the need for transfer, only when there is a clear inbound or outbound travel pattern at certain period of time, in absence of trip-attracting land uses along the spur branches.

Spur lines may serve small-sized city that is surrounded by mostly low-density, non-mixed land uses, in which interlaced scheduling allows higher frequency along the urbanized segment where the lines overlap.

To ensure network simplicity, transfer opportunity between trunk lines must be considered when inbound and outbound travel demand pattern is less discernible. Spur lines aren’t recommended for high demand rail corridors, as they dissipate the effective frequency on the main line.


Complex travel pattern requires simpler network solution

Special caveat to this rule: Branching or spurring of a few number of frequent lines can work well in an open system BRT network,  resulting in even higher combined frequencies along the busway:

  • Main trunk lines are designed to run along dedicated BRT corridor to primarily provide direct, on-route transfer opportunities to local routes, without ever leaving the BRT right-of-way
  • Some trunk lines can be designed to split off from the BRT corridor to access off-route areas which are typically characterized as low density and low traffic areas, with lower chances of traffic delay impacting the regularity of the combined headways of all services that share the interlined segment of the BRT corridor

Bus route 83 utilizing the Auckland North Shore Busway is a fine example of simultaneous application of branching and through-routing principles.

Timed transfer or pulse

A pulse is a timed transfer across multiple routes. Pulsing encourages ridership on low frequency routes, and expands the connective network effect to low frequency routes. It is very useful on corridors with different frequency and vehicle capacity requirements.

Nonetheless, planning for a many-to-many pulse is a very challenging task, due to the following requirements:

  • Reliability (as delay in just one direction would impact others)
  • Schedule-ability (as synchronization of headways and travel time segments for all affected routes reduces flexibility in scheduling off-duty times)
  • Advance arrival-based trip planning (when pulsing involves transferring from high to low frequency routes)

One-to-One (End-to-End) Pulse

  • Recommended for corridor segments with change in frequency or vehicle capacity requirements
  • When both routes have similar low frequencies and vehicle capacity requirements, it is better to combine the routes together (through-routing)

End-to-end pulse

One-to-Many (One-Way) Pulse

  • Recommended when travel pattern is tilted to only one direction (i.e. inbound pulse during am peak, outbound pulse during pm peak)
  • Synced arrival delay can be avoided with extra few minutes buffer time allowance between feeder and trunk arrivals
  • Highly recommended when both routes have similarly low frequency levels

One-way pulse

Many-to-Many (All-Way) Pulse

  • Recommended when there’s bidirectional travel pattern along one or more routes
  • Synced arrival delay can be excessively long for routes with high headway variance

All-way pulse