Line S45 of the Vienna S-Bahn, also known as the Vorortelinie (lit. Suburban Line) or Wiener Vorortelinie (lit. Vienna Suburban Line), is an electrified commuter rail service operating in Vienna, Austria.
|Opened||31 May 1987|
|Line length||16 km (9.9 mi)|
|Number of tracks||2|
|Track gauge||1,435 mm (4 ft 8+1⁄2 in) standard gauge|
The S45 is the only S-Bahn route to operate entirely within Viennese city limits, and it is the most frequently operated single S-Bahn service, with intervals of 10 minutes during weekdays and 15 minutes during weekends and holidays.
The S45 opened on 31 May 1987. It follows the route of part of the original Stadtbahn and still bears the architecture of the original Stadtbahn. Drivers based in Wien Franz-Jozefs Bahnhof and Wien Westbahnhof operate trains on the route. Unlike the Pink line or the “Stammstrecke” (lit. stem route), it is the only line servicing the route. It terminates at Handelskai (on the Stammstrecke) and also crosses the U6 there, the U3 at Ottakring and joins both ends of the U4 at Heiligenstadt and Hütteldorf.
Due to the short platform lengths, only single 4024s (Talent EMUs) and 4020s can operate on the route. The 474X train sets were also tested on the route, but it was found that their extendable door step took too long for them to be able to maintain good time on the route.
The maximum speed of the route is 100 km/h, between Hütteldorf and Penzing; however this speed is not always reached due to the way the route is signaled (i.e. due to the limitations of PZB90, which however don't apply to all 4020 EMUs as most of them use the outdated Indusi60).
The original route was opened on 11 May 1898 by the Vienna Stadtbahn. Steam powered trains operated between Wien Hütteldorf and Wien Heiligenstadt on a single track line. On 11 July 1932, passenger service was ended and only freight trains used the line.
In 1975 freight service was discontinued and the line was abandoned. In 1979 the City of Vienna, along with ÖBB brought up plans to reactivate the line. In the following years the line was renovated, expanded to two tracks and electrified with 15 kV 16,7 Hz.
In 1984 a final plan of the new route was concluded. Service began on 31 May 1987, nearly 55 years after passenger service was discontinued, between Hütteldorf and Heiligenstadt.
Passenger traffic greatly increased when service was extended past Heiligenstadt to Handelskai in 1996, offering a connection to the Vienna Trunk Line and increased even more when the U3 U-Bahn line was extended to Ottakring.
In 2007 rush hour frequency was increased from 15 minutes to 10 minutes and in December 2012 frequency was increased to 10 minutes on weekdays.
From 15 December 2019, it is one of the routes where frequency have been increased with expected arrival every 10 minutes until 9PM. The move is expected to increase the connectivity within the city. 
ÖBB: R, REX, CJX
Bus: 43B, 47B, 49A, 50A, 50B, 52A, 52B, 53A, N49
|Opened in 1858 as part of the Western Railway, Stadtbahn section opened in 1898.|
Bus: 45A, 46A, 46B, 48A, N46
|U-Bahn connection opened in 1998.|
Bus: 42A, 44A, N43
Bus: 10A, N41
|Wien Krottenbachstraße||Bus: 35A, N35|
Bus: 5B, 10A, 11A, 38A, 39A
ÖBB: R, REX
Bus: 5A, 11A, 11B, N64
|Service extended in 1996.|
- Vorortelinie wird ab 1987 bis Hütteldorf fahren, Arbeiterzeitung, 23 March 1984 - 27 March 2010
- "Massive investments improve Vienna S-Bahn capabilities". www.themayor.eu. Retrieved 2020-04-09.