Low-density suburbs present a unique challenge for designing an effective bus network. For reasons of geometry, it’s cost-prohibitive to run a direct bus between each suburban corridor and the center city, or to build a grid of ultra-frequent routes running along each arterial. Instead, suburban bus networks are generally organized on the “trunk-feeder” system. A high-capacity route runs between the center city and a suburban transit center, and a series of shorter and less frequent routes run between the transit center and the rest of the suburban area.
Metro has long used this principle to guide its service planning in Kent and Renton. Route 150 provides frequent all-day trunk service between the Kent Transit Center (TC) and downtown Seattle, via the Southcenter Mall (also an important connection point), while Route 101 acts as the trunk between Renton TC and downtown. A pile of other routes connect to one or more of these transit centers, including the 105, 148, 156, 164, 166, 168, 169, 180, and 183. In addition, Metro operates a handful of park and rides (P&Rs) that are also useful as connection points, most notably the South Renton P&R.
When Central Link opened in 2009, it instantly created a new super-high-capacity trunk line, running very close to the 101 and 150. Many people expected Metro to propose an extensive reorganization of Kent and Renton service, moving connection points from the existing transit centers to the new light rail stations. While Metro did reorganize some services, it made few changes in Kent and Renton. To this day, the 101 and 150 each have a long freeway-running segment that largely parallels Central Link.
Riders in Kent and Renton have been resistant to change; they like having a quick one-seat ride to downtown. However, the current network leaves much to be desired. Route 101 only comes every half hour, and it makes a time-consuming detour to South Renton P&R on its way to Renton TC. Route 150 does run every 15 minutes, but it spends 15 minutes slogging through Southcenter, a path that would take 5 minutes to drive. These deviations represent a significant time sink for the riders who aren’t using them.
To compound the problem, a significant number of riders aren’t stopping at the end of the route — they’re connecting to one of the feeder services. How many people are we talking about? Well, Routes 101 and 150 have a combined total of 12,100 daily riders, while the feeder routes have a total of 17,000 daily riders. The correlation isn’t exact; some of the riders on the feeder routes aren’t connecting to the trunks. However, it’s clear that a significant fraction of the people riding the 101 and 150 are already making a two-bus trip (and a slow one, at that).
I want to show you that it doesn’t have to be this way. I’ve put together a draft of a proposed all-day network reorganization for Kent and Renton. If implemented, this network would improve travel times for virtually every possible trip between Kent/Renton and points north. And it wouldn’t cost a penny more than what we’re already spending. In fact, in terms of service hours, it would be 4% cheaper than the current network.
The map (see above) depicts the ten routes that would be part of the new Kent/Renton all-day network. The three most important activity centers — Southcenter, Kent TC, and Renton TC — each have 10-minute service to Rainier Beach Station. Each route in the network operates at a multiple of the Link base frequency, with a timed outbound connection to designated trains. The full frequency chart is below.
The strength of a frequent network is its ability to accommodate spontaneous travel. Outside of peak hours, riders generally aren’t taking scheduled trips. Therefore, the best estimate of travel times also takes frequency into account. Since a rider is equally likely to want to take the bus at any time, their average wait time will be half of the scheduled gap between trips.
To illustrate the advantages of this network, I identified a number of sample trips, and calculated their average end-to-end time using both the old and new network. Since the network is focused on (spontaneous) off-peak travel only, I have included wait time in the estimates for each of the below trips, even for the first leg. For trips that use timed connections, I assume that it takes 2 minutes for a rider to switch vehicles. All trips are calculated based on roadway conditions at noon on a weekday.
Here are a few examples :
Southcenter to Westlake: 0:48 -> 0:46
Westlake to Southcenter: 0:45 -> 0:43
Kent TC to Westlake: 1:10 -> 1:08
Renton TC to Westlake: 0:58 -> 0:56
Kent TC to Beacon Hill: 1:03 -> 0:59
South Renton P&R to Capitol Hill (U-Link): 1:02 -> 1:00
Green River CC to Westlake: 1:55 -> 1:43
Renton Highlands to Capitol Hill (U-Link): 1:32 -> 1:13
The travel time between downtown and each of the major regional centers (Renton, Kent, and Southcenter) are essentially unchanged. The travel time between downtown and anywhere else is slightly shorter. But the real advantages are for the majority of riders who are currently connecting in Kent or Renton. The trip from Green River CC to downtown Seattle is 10% shorter; the trip from Renton Highlands to Capitol Hill (assuming the existence of U-Link) is 20% shorter. All current riders of Kent/Renton feeder services will see a similar advantage.
There are some other minor, but real, benefits of this change. For example, there will be fewer buses in the downtown transit tunnel, which will reduce delays for Link and the bus routes that remain.
So, what will it be? Will we keep running the inefficient network that we currently have? Or will we make a change that will improve 20,000 daily trips? I know what I’d choose.
A few notes:
- I am not proposing any changes to Metro’s peak network. The routes I propose to delete during the off-peak (the 101 and 150) would still survive as peak expresses, just like the 15, 17, and 18 expresses survived the RapidRide restructure.
- For the sake of focus, the map does not depict any routes or route segments north of Rainier Beach. In practice, just like today’s 106 continues north of Rainier Beach, one or more of the new Renton routes would probably continue north as well.
- Once again, I would like to put in a pitch for rerouting Sound Transit’s Route 578 through Kent, and for adding a Federal Way stop to the 594. While the 578 is not frequent, it would provide the fastest possible route between Kent and downtown Seattle, and at virtually zero cost.
Every 10 minutes
106+169: Rainier Beach – Renton TC
164+180: Rainier Beach – [I-5] – Southcenter – Kent TC
Every 15 minutes
A (red): Tukwila Int’l Blvd – Federal Way TC
F (red): Burien TC – Renton
Frequent (every 20 minutes, timed Link connection)
106 (grey): Rainier Beach – Renton TC – Renton Highlands
149 (orange): SeaTac/Airport – [SE 180th St] – Fairwood
155 (brown): SeaTac/Airport – Highline CC – Kent TC
164 (black): Rainier Beach – Kent TC – Green River CC
169 (green): Rainier Beach – Renton TC – [SR-515] – Kent TC
180 (purple): Rainier Beach – Kent TC – SE Auburn
Local (every 30 minutes, timed Link connection)
107 (blue): Rainier Beach – Renton TC
165 (blue): Burien – Highline CC
168 (blue): SeaTac/Airport – Kent – Maple Valley
184 (purple): Tukwila Int’l Blvd – [Military Rd] – Federal Way