Untangling Transit Spaghetti

Too often, public transit networks are too complex. On a map, these lines look like a plate of spaghetti. Spaghetti is delicious, but it doesn’t make for a good transit network design. Complexity results from having too many competing route choices. Too much route choice is inefficient, and is overwhelming for users.

A Recipe for Spaghetti

What leads to transit spaghetti lines? One-seat rides, and route-focused design.

The first source comes from emphasizing “one-seat rides.” Many bus networks create “one-seat rides” that connect as many origins and destinations as possible. This may seem like a good idea, but it creates a lot of routes.

Maximizing one-seat rides also means sacrificing higher frequency service because more routes means few resources for each route. Granted, having fewer one-seat rides means that passengers will have to walk more. It does however ensure that most passengers have access to frequent, reliable, and high capacity service.

Second, optimizing individual routes rather than the entire system also leads to transit spaghetti. Routes are usually designed incrementally, isolated from the larger transit network. As a result, some routes end up competing against each other.

For example, two routes may get you to the same place, but have different starting points. This means you must choose one route or the other, when ideally you could catch either. This duplication of routes is inefficient and not useful for transit users.

Alternatively, when two or more routes do share the same alignment, their schedules should complement each other. But too often, vehicles arrivals are scheduled unevenly or worse scheduled together, which increases wait times, and reduces the usefulness of having multiple choice.

A Straightforward Solution

When it comes to designing transit networks, simple is better. I’ll use Honolulu’s bus network as an example. Honolulu exhibits all the classic symptoms of transit spaghetti:

  • An abundance of routes. Currently, there are over 50 routes that all converge in Downtown Honolulu.
  • Competing route alignments. When traveling from Downtown to the nearby Capitol District, you must choose whether to board routes on Hotel St or on King St. If these routes were on the same street, you’d see a bus coming every 40 sec on average in peak periods.
  • Uncoordinated schedules. Routes 55, 56, 57, and 57A share the same alignment between Nuuanu, downtown Honolulu, and Ala Moana (Route 56 doesn’t always go to Ala Moana). Theoretically, when scheduled as a corridor these routes could come consistently every 5 min. However, these routes are scheduled independently, which means you may wait just 30 seconds or up to 30 minutes for the next bus.
A map of existing bus routes in Downtown Honolulu
Existing bus routes in Downtown Honolulu.

Honolulu’s urban bus network can easily be redesigned and rebranded into a simpler network. The map below reimagines Honolulu’s urban bus routes as three high frequency bus lines (5 min headways or less), one frequent bus line (15 min headways or less), and three urban circulators, which provide direct connect to nearby residential area and medical designations.

A conceptual map of high frequency bus routes in Downtown Honolulu
Downtown Honolulu high frequency bus map

This new bus network relies on:

  • High frequency bus corridors. All routes converge to share identical routing through downtown. Instead of having too many mediocre route choices, users now have one or two excellent route choices.
  • Synergistic scheduling. Fewer route alignments means that routes can be grouped together to produce higher frequencies. Frequent transit service reduces wait time, makes transferring easier, and alleviates a bunch of reliability problems.

This conceptual transit network, though not perfect, is achievable with current transit resources. In fact, it relies on a reduction in bus service through the downtown area. This downsizing becomes possible after Honolulu’s rail system becomes the primary transit mode between the central business district and outlying suburban areas.

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