Zurich Stadelhofen already runs at a tempo most buildings never meet. It is the canton’s third-largest station, with three tracks pressed between the old town and the Hohe Promenade. According to Baublatt, a train passes through roughly every 90 seconds. Daily ridership figures differ by year and by method. SRF reported about 83,000 people boarding and alighting in 2019 and “more than 80,000” in 2025. Drees & Sommer gives about 80,000 people and 770 trains a day, and SBB data for 2025 gives about 75,200. Every one of those numbers describes a station with no spare room.

SBB’s answer is to build into the hill rather than out into the city. Track 4 goes about 35 m into the slope, at the level of the existing shopping passage, and three new tunnels come with it. A second Riesbach tunnel of about 1.4 km runs towards Tiefenbrunnen, a second Hirschengraben tunnel of about 600 m towards HB, and a second Zürichberg tunnel of about 290 m towards Stettbach. SBB states the purpose plainly: «Mit dem Ausbau des Bahnhofs Zürich Stadelhofen wird der Engpass im Zürcher S-Bahn-Netz beseitigt». Baublatt reports a gain from 22 to 32 trains per direction per hour, and SBB gives +50% station capacity.

The topology behind the stone

Read Stadelhofen as a node, not as a building. The canton argues that a sensible increase in S-Bahn service is possible “nur gemeinsam mit einem Ausbau des Bahnhofs Stadelhofen um ein viertes Gleis”. PAZ covered the other half of that pair in the Brüttenertunnel piece: four tracks to Winterthur buy stability, not speed. If you widen the corridor and leave the station at three tracks, the queue simply moves to the old town. The ETH Zürich expert report behind the federal priority list, which the canton calls the “Gutachten Weidmann”, reasons in the same network logic.

The architecture follows that logic. “Elysion”, by Giuliani Hönger Architekten with Caretta, won SBB’s anonymous 2019 competition with a unanimous jury. The station grows inward and upward. The side wings gain new storeys, and the central entrance drops to forecourt level, so the Stadelhoferplatz door becomes the main door again. Three links tie track 4 to the passage. SBB praised the design’s «stimmige Verbindung von Erweiterung und bestehenden Strukturen». The building it extends is Santiago Calatrava’s 1990 station, built for the launch of the S-Bahn. A fourth track was left out at the time to save about CHF 50 M, which is why the hill still has room for one. On the city side, the Tiefbauamt is planning an underground pedestrian link to Heimplatz, the Kunsthaus and the university quarter.

←TODAY: A CHF 1,700 M estimate (±20–50%) sits in the 2027 Botschaft, conditional on extending the rail VAT levy.
→3012: Stations become layered hillsides: rail in the rock, plazas in the light, nothing widened.
Fulcrum: Capacity won by depth instead of footprint only works if each layer can be built while the one above keeps running.

The cost estimate went from CHF 900 M in 2019 to about CHF 1.1 bn, then to CHF 1,700 M in the UVEK fact sheet of 19 June 2026. That figure is at June 2025 project and price levels and excludes VAT and inflation. Its stated accuracy is ±20–50%, and the fact sheet labels it as an estimate. The Federal Council made construction depend on extending the rail VAT levy, which runs to 2030 and needs a popular vote, expected in 2028. On 3 September the Zurich Regierungsrat, under Carmen Walker Späh, asked for the project to go ahead regardless. Tsri reported on 28 September that SBB listed it among seven «dringend notwendigen» projects. The consultation closed on 9 October. The trade-off is plain: waiting on the vote keeps the federal finances honest, but it leaves the S-Bahn’s tightest node on a timetable that no engineering decision controls.

Some of the people who matter here will never appear in a render. As SRF reported, a crew drove an exploratory tunnel 23 m into the ground in early 2025, at about 2 m a week, while the buildings above were monitored to the millimetre. The tunnel will later serve as an emergency exit. Those surveyors and miners are the reason a hill under the old town can be read at all.

Atelier: An office that designs next to live infrastructure has to treat the operating rhythm as a design input, much like a fire code. With a train every 90 seconds, every crane lift, every façade panel and every temporary entrance has to be planned around the timetable. Monday move: add a “must keep running” layer to your Archicad template, and draw the access routes, escape paths and service windows on it before you draw any new volume.

Hack: Turn a capacity claim into seconds of headway, so you can check it at your desk. Trains per hour are an abstraction. The seconds between trains are what a platform edge, a door and a crowd actually have to absorb.

for tph in (22, 32):
    print(tph, "tph:", round(3600 / tph), "s between trains per direction")
print(f"service gain: {32/22 - 1:.0%}")

The headway drops from 164 s to 112 s per direction, a 45% service gain. SBB’s +50% is a station-capacity figure, so the two numbers measure different things. Know which one you are designing to before you size a stair.

Next time a client’s brief says “more capacity”, ask for it in seconds. Then draw the layer that has to keep running before you draw the one you want to add.