Evolution of Urban Guideways

Sound Transit Link construction along I-5 (North Seattle by NE 145th St by author)

While traditional steel rail works well on the surface, Sound Transit and many other transit agencies favor elevated tracks in more semi-urban areas (tunnels in the urban core). To expedite construction of elevated guideways for the 1962 World's Fair, Seattle turned to Germany for trains to run on a prefabricated monorail. Now another German manufacturer is testing a prefabricated dual guideway system with integrated maglev propulsion.

While regional rail (e.g., Sounder) runs mostly at grade, for the metro area grade separation avoids conflicts with cars, bicycles, and pedestrians. Sound Transit's Link 1 Line would have far less service interruptions if it were grade separated in Rainier Valley. Going underground can help but construction is complex, time consuming, carbon intensive and expensive. Tunneling is often challenging because downtown underground infrastructure is complex (parking, foundations, utilities...). To avoid such infrastructure, the tunnel may need to go deep, complicating access for riders. Elevated guideways seem to be a good alternative. There is plenty of expertise building elevated roadways in the States, which construction companies have applied to rail. As seen on the picture above, Sound Transit is building towers, connecting them with 3 prefabricated girders, and then connecting and broadening them into a roadway". On top of the roadway, they construct the railbed, siderails and/or sound insulation panels on the side and the towers with overhead wire. The roadway is also used as a fire escape route. Many construction steps are required, so that construction typically takes several years to complete. To allow for construction equipment access, Sound Transit usually clears an 80ft corridor around the track.

MonorailSeattle Monorail (wikimedia by Klaus with K)

For the 1962 World's Fair, Seattle used prefabricated towers and monorail beams to quickly build the guideway, and Alweg provided two train sets. Each train has rubber tires: 16 wheels on top of the rail and 48 wheels to guide the train on both sides. The tires don't squeak as steel tires sometimes do, but are still audible. A power rail is attached to inside of the monorail track to power the train. While a monorail is visually far nimbler and faster to build, monorail systems are optimized for elevated lines. They cannot be used at-grade due to the exposed power rail and underground operation is difficult as it requires a larger than usual tunnel. For longer lines you also need to consider fire escape routes. Alweg licensed their technology to Hitachi. Bombardier and Hitachi still manufacture monorail systems. Bangkok just opened another line. BYD started to sell battery operated monorail systems.

TSB Dual-guideway Regional MaglevTSB guideway (by Max Bogl Group)

While Alweg ceased operation, several other German companies continued to develop rail alternatives. Transrapid developed a high-speed guideway system with integrated maglev (magnetic levitation) propulsion. While it did not get any traction" in Europe, Transrapid built a line serving the Shanghai airport, CRRC continues to refine and build trains, and others are using it to develop Hyperloop systems.

One of the manufacturers of the Transrapid guideway, Max Bogl Group, decided to use their expertise to develop a fully integrated regional transportation solution for moderate speeds of up to 100 mph called TSB (Transport System Bogl). Rather than surrounding a single track like a monorail or the Transrapid does, it uses two concrete guideways with are both open towards the middle for the propulsion arms of the train to glide through. The propulsion arms contain linear motors, which propel and lift up the train to allow frictionless travel except the connection with the power track below. When the train has stopped it rests on the power track. Each prefabricated guideway beam can span a distance of up to 120 feet. This configuration not only provides for a clean look, but also protects the technical components from rain, simplifies manufacturing and installation, and reduces site impact. A metal grate connects the two guideways and provides an escape route. Access is provided via emergency exits at the front and rear of the train. A single tower can hold two sets of guideways.

The TSB guideway technology can not only be used for elevated alignments, but also for bridges with up to 240 feet spans, at-grade, or tunneled sections. TSB's maglev propulsion allows for much steeper (10%) grades than steel wheels. That allows an elevated guideway to dip down for a station closer to the ground, or to hump up underground to a shallow station. Coming up from a shallow tunnel to an elevated line can be accomplished within 400 feet. TSB's guideways allow for fairly tight turns and branches which can switch a track in 15 seconds but do not allow for crossovers. Because TSB's train floats within the guideway channel, travel is smooth and quiet. There is no need for any sound barriers as traditional tracks require.

Vision for Berlin Hauptbahnhof Station (by Graft Lab)

Max Bogl Group has been testing the TSB for both transit as well as freight transportation for a few years. They also worked with a licensee in China to build a test track in Chengdu. Now Munich, Hamburg, and Berlin are considering building TSB lines to expand their existing transit network as building such a line is less carbon intensive, more affordable and faster to build than to expand their subway network, and less disruptive than laying tracks for a tram, while providing faster and higher capacity than a tram.

Some of the same considerations would apply to Seattle. While those three cities are mostly flat, Seattle has major hills. When Sound Transit built the first downtown line, it skipped building a station on First Hill as it would have to be very deep. It would be much easier to build it as a TSB line. How much faster could Sound Transit expand their network if it used more modern technology such as TSB?