Busway for SeaTac Airport

To accommodate growing passenger and cargo levels, the Port of Seattle plans to build new terminal for SeaTac Airport with their Sustainable Airport Master Plan. In addition, Concourse C will be expanded with 4 additional levels. There's a slew of other projects but this article will focus on the transportation aspects for passengers and travelers. While earlier plans had called for a new people mover, the latest plan will only build an elevated busway.

Proposals

The SeaTac website is not organized well, so below is an easier table to find their previous documents.

Description	Link
Draft NEPA (2024)	https://www.airportprojects.net/sampntpenvironmentalreview/materials-2/
SAMP Scoping (2019)	https://www.airportprojects.net/sampntpenvironmentalreview/2019-scoping-process/
SAMP Concepts (2017)	https://wstc.wa.gov/wp-content/uploads/2019/12/2017-0725-BP9-SAMP.pdf
SAMP update (2016)	https://www.scribd.com/document/335776181/Port-of-Seattle-Sustainable-Airport-Master-Plan-Update-July-2016
SAMP presentation (2015)	https://wstc.wa.gov/wp-content/uploads/2020/01/2015-0519-BP12-PortofSeattle.pdf

Near term project: New Terminal and Elevated busway

The draft NEPA (National Environmental Policy Act) Environmental Assessment outlines the 30+ projects and solicits the public's input by December 13th, 2024. Chapter 1 provides a quick overview.

SeaTac SAMP draft NEPA proposed action mapNew North Terminal (T01 and T02)

The new north terminal consists of two projects: the North Gates T01 concourse and the North Terminal Building T02 itself.

New Terminal map

The new multi-level terminal concourse and aircraft apron will accommodate up to 19 gates. The new concourse would have a footprint of approximately 203,000 square feet and contain three levels (approximately 609,000 square feet total) including:

• Ground/Ramp level: for baggage handling and aircraft support functions.
• Concourse level: consists of passenger areas, concessions, restrooms, and other
  passenger and airline support functions.
• Mezzanine level: holds office space.
• Elevated pedestrian walkway: provides access to the passenger terminal.

The other part is the Second Terminal and Parking. This includes construction of a new multi-level passenger terminal across the expressway. The new terminal would be approximately 575,000 square feet in size, with a footprint of approximately 166,000 square feet. The new terminal would include:

• Basement level: for baggage handling and screening.
• Baggage claim level: for arriving passengers.
• Open mezzanine level: connected to a new garage that provides commercial curbside space.
• Departures level: with passenger check-in and security screening facilities.
  The new terminal also includes a new multi-level parking garage to provide approximately 1,350 parking spaces.

Earlier 3D rendering of the new north terminal with larger terminal and people mover

Please note that the gates (west of roadway) and the terminal (east of roadway) are two separated buildings connected by the passenger bridge. Passengers will need to check in at the terminal before crossing the bridge.

Elevated Busway (L02)

Since the original terminal and the new Northern Terminal are disconnected, SeaTac plans to build a 6000 feet long elevated busway to connect them together. Note that the elevated busway is for pre-security passengers (before entering through security) unlike the existing airport people movers for post-security passengers (after entering through security).

The elevated busway will have three stops:

1. North end of the Central Garage
2. New North Terminal
3. Consolidated Car Rental Facility

Northeast Ground Transportation Center (L04)Top existing walk, bottom rendering of Northeast Ground Transportation Center from Port of Seattle

At the north end of the existing Central Parking Garage, the Port of Seattle will build a new NE GTC (Northeast Ground Transportation Center) for the new elevated busway connection. The NE GTC will also provide a sheltered walk from the Link light rail station to the airport terminals.

Level		Description
Four and Five	Office space	Approximately 52,000 square feet per level for office workers
Three	Passenger circulation and check-in facilities	Providing waiting space for passengers arriving / departing the elevated busway and Link light rail
Two	Shuttle bus platform	Southern terminus of elevated busway
Ground	Charter and cruise bus lot	Expansion of existing bus lot

Here's a map of the various additions annotated with the major projects. Initially the existing terminal concourse (beyond security) will not be connected to the new terminal concourse. Transferring passengers between the terminals may have to leave security and use the shuttle bus along the busway.

Stride Connection

Notably, the elevated busway's Consolidated Rental Car Facility stop is relatively close to the Tukwila International Boulevard Link Station (TIBS) and future Stride 1 freeway BRT station.

For airport travelers from Bellevue, it might make sense to use Stride 1 BRT to TIBS freeway BRT station, then walk south over to the Consolidated Car Rental Facility and then use the busway shuttle to get to the new or even the existing terminal instead of riding Link for one stop.

One major blocker for such a use-case is the lack of good pedestrian access to the rental car facility from the north east end. Currently few travelers use such a route.

Previous alternatives for New Terminal and Shuttles

Back in 2016/2017 (Urbanist article), the Port of Seattle was deciding between two larger alternative layouts for the new terminal. For now, the Port decided to only build out the southern wing, a northern wing may come later.

2017 Shuttle Options

In 2017 five different options were studied to connect the two terminals and the rental car facility: four people mover alignments and a busway.

Option Map Overview	Description
	People mover at (north 4th floor) central garage, new north terminal and rental car facility
	People mover at (middle 6th floor) central garage, new north terminal and rental car facility
	People mover at (south 6th floor) central garage, link station, new north terminal and rental car facility.
	People mover at (south 6th floor) central garage, link station, new north terminal and rental car facility.
	Elevated busway at south central garage, north central garage, new north terminal and rental car facility.

Chart of people mover options

Option 1 had the simplest construction given the few changes to the existing parking garage. Option 2 through 4 added an additional station in the central garage for easier pedestrian access though require larger changes to the central garage.

The option 1 alignment was converted from a people mover line into an elevated busway to reduce cost or to allow integration with other bus services.

Additional Ideas

Appendix L of the NEPA Environmental Assessment covers surface transportation. Unfortunately, very little is spent on transit connections, by far most of it covers road access and traffic implications. Only a few pages discuss access by public transit. The good news is that shuttle, charter, and Sound Transit buses have great access to the new terminal and won't get stuck in traffic anymore and the new ground transportation facility will allow both bus (whether they arrive via the busway or International Blvd) and Link riders to check-in at the new ground transportation facility. Hopefully this will include baggage drop-off. While Link riders can hop on the shuttle to get to the new terminal, they still need to walk a quite a bit to the main terminal, in particular to the International Terminal. If you arrive at the International Terminal and need to transfer at the new terminal or pick up a rental car, you will also need to walk quite a bit, possibly with luggage. This could be addressed by extending the shuttle bus route along the current shuttle route within the central parking garage and extending the new elevated busway on the east side of the parking garage to connect with the proposed busway towards the new terminal and rental car facility.

An elevated people mover loop like LAX airport is building would address such need, too:

People mover loop (SAMP map annotated by author)

The people mover could run above the sky bridges (between the main terminal and the central garage) and connect via escalator to the main terminal mezzanine. It may provide stops at the center of the main terminal (or at both ends), the new terminal, a stop at the north end of the rental car facility to allow access from TIBS, and at the airport Link station. Alternatively, the people mover could use the existing shuttle corridor within the central parking garage. Buses may not need to enter the airport but use International Blvd (as Metro buses currently do) to access the people mover. Munich Airport has been considering building a loop using TSB maglev technology. It might be fast enough to use a single direction loop rather than a bidirectional one as LAX is building.

Make sure you comment on the Port's proposal by December 13th.