There’s a thread on Twitter by Stephen Smith bringing up Zurich’s S-Bahn as an alternative to extensive metro tunneling. It reminded me of something I’d been meaning to write about for a long time, about how S-Bahn tunnels, in Zurich and elsewhere, include not just the bare minimum for through-running but also strategic tunneling elsewhere to reach various destinations not on the mainline. Zurich’s S-Bahn includes about 19 km of tunnel built since the 1960s, which is similar per capita to the amount of tunneling built for the Washington Metro.
Such tunneling is important to ensure a regional rail network reaches destinations off the mainlines. Even cities with metro systems need to understand this as long as they have some mainline rail serving suburban destinations. For example, in the Center of Israel, Tel Aviv is getting a subway-surface light rail network, but outside the urban core rail transport will remain dominated by Israel Railways service; as Israel Railways avoids many city centers, such as Netanya, short strategic tunnels are critical.
Tunnels in Zurich
The core of the Zurich S-Bahn is three city center tunnels: the 2 km Käferberg Tunnel from Oerlikon to Hardbrücke, the 7 km combination of the Hirschengraben Tunnel and the Zürichberg Tunnel from Hauptbahnhof to the Right Bank of Lake Zurich and points northeast, and the 5 km Weinberg Tunnel from Hauptbahnhof to Oerlikon and points north. The Käferberg Tunnel is from the 1960s, the Hirschengraben and Zürichberg Tunnel opened in 1989-1990 as the core of the Zurich S-Bahn, and the Weinberg Tunnel opened in 2014 as a second S-Bahn route to add more capacity.
These 14 km of tunnel look like any standard picture of regional rail tunneling. However, Zurich has in addition built a 5 km tunnel for a loop to the airport. Without this tunnel, no regional or intercity rail service to the airport would have been possible, as the airport was at a distance from the mainline; only trams could have served the airport then.
In addition to these 19 km, there is some talk of building an additional tunnel of 7-10 km on the Zurich-Winterthur Line, called the Brüttener Tunnel, to speed up service between these two cities.
Tunnels on other regional rail systems
In Paris, the RER consists not just of legacy rail track and city center tunnels, but also outlying tunnels reaching new destinations. The RER B connection to Charles de Gaulle Airport is new construction, opening in 1976 as a commuter line just before the RER opened and incorporated it as a branch. It’s a mix of above- and underground construction, totaling 5.5 km of tunnel. Two more key RER lines, at both ends of the RER A, are new: the branch to Cergy, which opened between 1979 and 1994 and has 3 km of tunnel, and the branch to Marne-la-Vallée, which opened in stages starting on the same day as the RER A’s central tunnel and continuing until reaching its terminus in 1992.
All three new RER branches are busy. They have to be – if there weren’t so much demand for them, it would have been financially infeasible to build them and those areas would have had to make do with a bus connection to the existing mainlines. The Marne-la-Vallée branch carries about two thirds of the eastern branch ridership of the RER A, making it most likely the busiest single rail branch in Europe.
In London, the regional rail network is less modern than in Paris, Zurich, and other cities with extensive development of new tunnels. Nonetheless, the Crossrail plans do include a short outlying tunnel reaching Heathrow Airport. Moreover, one of the two eastern branches of the mainline has the characteristics of an outlying tunnel, namely the branch to Canary Wharf. Canary Wharf is only 5 km from the City of London and the tunnel connecting to it is contiguous with the central tunnel, but the branch is not really about improving connections to onward suburbs. Where La Défense was always on the way to western suburbs on the RER, Canary Wharf is only on the way to Abbey Wood. There are proposals among area railfans to extend this branch much farther to the east, but no official plans that I know of. In the currently planned paradigm for Crossrail, Canary Wharf is purely a destination.
In Munich, there is a new line toward the airport, with some tunneling on airport grounds as well as at two intermediate suburban stations. There is also a short above-ground spur connecting the airport to the western side of the S-Bahn, giving it two different routes to city center. Finally, there is a short tunnel slightly to the west of the main trunk tunnel to better connect S7 to the mainline.
Why are airports so prominent on this list?
The concept of using strategic tunnels to build new spurs and loops to connect mainlines to new destinations has nothing to do with airports. And yet, so many of these spurs connect to airports: Charles de Gaulle, Heathrow, Zurich, Munich. There are many more such examples, on regional or intercity lines: Schiphol, Arlanda, Ben-Gurion, soon-to-be Berlin-Brandenburg, Barajas. Why is that?
The answer is that the purpose of a spur or loop is to connect to a destination off the mainline. European cities for the most part developed around the railway or metro line. Virtually every important destination in London is on a legacy railway because during the city’s 19th and early 20th century growth period, the railway was the only way to get to Central London. Airports are consistent exceptions because they’re so land-intensive that it’s hard to site them near existing railways.
Where non-airport destinations somehow had to be developed away from the mainline, they’re attractive targets for spurs as well. Canary Wharf sits on the site of a disused dock, which generated some freight rail traffic but little demand for passenger rail. Cergy is one of several new towns built around Paris to act as suburban growth nodes, together with Marne-la-Vallée and Évry (served on a loop of the RER D).
In smaller cities than Paris and London, suburban growth often came together with a metro line. In Stockholm, the Metro was planned together with public housing projects, so many of the Million Program projects are right next to stations, facilitating high public transportation usage. There’s usually no need to build many new regional rail spurs, because such sites are close enough to the center for metro service to be quick enough.
The situation of regional rail in Israel
In Israel, urban development has ignored the railway almost entirely. The colonial network was weak and barely served the state’s travel needs. Investment was minimal, as the state’s political goals were population dispersal and Judaization of peripheral areas rather than efficient transportation. Towns were built around the road network, connected to one another by bus since people were too poor to afford cars.
Rail revival began in the early 1990s with the opening of the Ayalon Railway, providing through-service between points north and south of Tel Aviv. In the generation since, ridership has grown prodigiously, albeit from low initial levels, and the state has built new lines, with an ongoing project to electrify most of the passenger network. However, since the cities came first and the trains second, the new lines do not enter city centers, but rather serve them peripherally near the highway, often surrounded by parking.
Thus, Netanya’s train station is located to the east of the city’s built-up area, on the wrong side of the Route 2 freeway. Ashdod’s train station is on the periphery at a highway interchange, well to the east of city center. Ashkelon’s station is on the eastern margin. The under-construction line through Kfar Saba and Ra’anana passes just south of the built-up area.
In all of these cases, doing it right would require, or would have required, just short, strategic elevated or underground lines:
- Netanya is at the northern end of the Tel Aviv commuter rail network, and so it can easily be served by a spur. The existing station can be retained as a junction for intercity rail service, but building a commuter rail spur would not compromise frequency. Such a spur would require no more than 2 km of tunnel.
- In Ashdod and Ashkelon, there are north-south arterials that are so wide, 50-60 meters, that they could host cut-and-cover subways, effectively moving the line to the west to serve those cities better. In Ashdod there is a decision between going under B’nai Brith, which offers a more convenient through-route, and Herzl, which is more central but requires some boring at the southern end of the city.
- In Kfar Saba and Ra’anana, about 8 km of tunnel under Weizmann and Ahuza are needed, and could potentially be done cut-and-cover as well, but these streets are 30 meters rather than 50 meters wide. Such a route would replace the under-construction combination of a freeway and railway.
- In Rishon LeZion, a 6km route, not all underground, is needed to connect Rishonim with Moshe Dayan via city center and the College of Management rather than via the under construction freeway route avoiding these destinations.
Unfortunately, so far the state’s investment plans keep skirting city centers. It serves them with a cars-and-trains paradigm, which assumes the rail passenger is driving or riding a bus to the train station, never mind that in that case it’s more convenient to drive all the way to one’s destination. This suppresses ridership; not for nothing, the busiest station outside metropolitan centers is Rehovot, with 2.1 million annual entries, and not Ashdod, which is second with 1.9 million. Ashdod is a city of 220,000 and Rehovot one of 140,000, but Rehovot’s station is far more walkable. Were Ashdod not poor, few people would use the station at all – they’d all just drive.