The rail line along the south shore of Lake Balaton was built in 1861 as the Budapest – Székesfehérvár – Nagykanizsa railway. Within the Kingdom of Hungary, it was a main line to Adriatic ports. Its current status is an international route to Slovenia and Croatia, but with many intermediate stations, serving the tourist resorts along the lake shore. The line is electrified, but it is only single-track, with a speed limit of 100 km/h.
The discrepancy between function and capacity is great. The line is part of the Pan-European Corridor V. It is the main route from Budapest to Zagreb, Ljubljana and northern Italy. Although a motorway has been built parallel to the lake shore (M7 motorway), the rail line still awaits improvement. Because of the constraints along Lake Balaton, improvement will be difficult, and construction of a new high-speed line (HSL) even more so. There is an alternative route via Kaposvár, but it is longer. (The existing line via Kaposvár is also single-track).
A high-speed route toward Zagreb would start at Érd, on the outskirts of the Budapest agglomeration. From there, it would run parallel to the railway or M7 motorway, past Székesfehérvár, to Lepsény. (It would have a connection into Székesfehérvár station, but the main HSL would bypass the city). Only the section after Lepsény, along Lake Balaton, is considered here.
East of the lake, the HSL would follow the railway and/or the M7, to Nagykanizsa. There it would join the Drava plain HSL, creating a high-speed route to Zagreb, and to Maribor / Ljubljana via Kotoriba.
The south shore of Lake Balaton offers the only straight and level route, south-west from Budapest. The shallow lake is 79 km long. On the south side there are ridges at right angles, which terminate at the shore. (The ridges are up to 250m high, the lake itself is at 105m elevation). The bays between the ridges have silted up, forming a relatively straight shoreline. The 1861 rail line follows it closely, mostly within 200 m. If it was further from the shore, it would have cut the ridges – like the later motorway.
The 1861 alignment is good, and its eastern half almost straight. However, Lake Balaton is the main lake resort of Central Europe, and its shores are built up. Next to the line is almost continuous sprawl, typically single houses 15-30 m apart.
The problem is therefore: how to fit a high-speed line, into this semi-urban area. Even upgrading the existing line will face many problems. It has unfenced track in urban areas and the unfenced tracks are crossed by footpaths. The line has many single-track stations, with no passing loop, and expansion is difficult because streets directly adjoin platforms.
A new HSL would carry European-level services. The Lake Balaton region is a major destination, but one station is sufficient. The logical choice is Siófok, the largest town on the lake. Siófok station has enough room for expansion, as a HSL interchange station. However, not all trains would stop there, and it is not necessary that they all run through the station. The main HSL can bypass Siófok, and that makes the route options easier.
There are several options for a HSL along Lake Balaton:
- build a HSL along the M7 motorway. However, west of Siófok, a high-speed line cannot follow this motorway exactly, because it is too curved.
- an inland route separate from the motorway: it would cross the ridges at right angles.
- strip the existing alignment, and construct a new four-track line. That would require the demolition of hundreds, possibly thousands, of houses. It would also create a barrier between the lake and the urban area.
- build the HSL in a cut-and-cover tunnel, on the existing alignment, and build a light-rail line on the tunnel roof. This option also has 4 tracks, but the barrier effect is much less. However, a shallow tunnel would act as a dam, blocking groundwater flow into the lake, along its entire length.
- build a 4-track line on viaduct, on the existing alignment. It would be less of a barrier, but it would be more intrusive than a 4-track surface line.
- a HSL on viaduct in the lake, parallel to the shore. Construction in a shallow lake is probably easier than construction in an urban area. However, the viaduct would be at least 10 m high to clear boats, and visually very intrusive.
The HSL alignment suggested here is a combination of the inland options. Apart from the sections alongside the motorway, the alignments shown are indicative only.
The first section from Lepsény would run alongside the M7 motorway, bypassing Siófok about 2 km inland. This bypass (Balatonaliga to Zamárdi) is the oldest part of the M7. (If the HSL followed the rail alignment through Lepsény, it would first parallel highway 7, and then join the M7 at Sóstó Lake).
To access Siófok station from the east (from Budapest) only a 3-km spur line is needed. It would follow highway 7, starting at Sóstó Lake. About 4 km of line into Siófok station would be used by high-speed trains, but not running at speed. At present, there are no intermediate stations on this section. West of Siófok, fast trains would again use the existing alignment for about 3 km, and then rejoin the HSL via another spur line.
Click to enlarge: spur lines (yellow) connect Siófok station to HSL…
At Zamárdi, a newer section of the motorway begins (opened 2007). It crosses the system of ridges and valleys, at right angles to the lake shore. The motorway alignment is curved to minimise gradients and avoid ridge tunnels, but a viaduct was also needed.
Kőröshegy viaduct from the lake: image under CC3 license by Kleszczu…
From Zamárdi, the HSL would have its own alignment,, about 1500 m inland. It would be an almost straight line, about 30 km long. At Ordacsehi junction, east of Fonyód, it would rejoin the M7, on more level terrain. The price of a straight alignment is a series of tunnels. Fortunately, closer to the shore, the ridges are lower. The tunnels will also avoid built-up areas south of the shore, since these are built on the ridges.
Click to enlarge: schematic alignment of a HSL with ridge tunnels, at Zamárdi. The site and length of the tunnel sections is indicative only…
The alternating valleys and ridge tunnels at Balatonszárszo: note how the villages extend inland along the ridges…
The HSL at Balatonboglar: here too the villages extend inland on the ridges, but they are only 10-20 high where the HSL cuts them, in shallow tunnel or in cutting
After Ordacsehi junction, the HSL can follow the M7, in a wide curve around Fonyód. This area is flat, former marshland on a silted-up bay.
Click to enlarge…
The remaining alignment is determined by where the HSL crosses the last main ridge. This ridge extends south from Balatonberény: the motorway crosses it away from the lake, at an elevation of over 200 m.
On the 1910 Austro-Hungarian military map, the relationship of rail lines and terrain is clearer. The marsh (Nagy Berek) is visible as such, and east of it the large ridge. The HSL around Fonyód is superimposed in red. The new line could cross the ridge in tunnel (2-3 km), on an alignment between Balatonkeresztúr and Vörs (shown in blue).
Click to enlarge…
At Vörs, the HSL would join the existing rail alignment (line to Nagykanisza). Alternatively, it could follow the motorway, and join the existing line further south. A tunnel is probably unavoidable. (The motorway does not need a tunnel, but its gradients are steeper).
The simplest option is to build the new line around the ridge, like the existing line. (The HSL would be about 500-1000m further south). A short tunnel would go under part of Balatonberény: the rest would probably not need tunnels, since the ridge is lower here.
Click to enlarge… new line around the tip of the ridge at Balatonberény…
The HSL alignment proposed here, would be about as long as the existing line. It would however dramatically improve capacity and speed. If transit freight is re-routed to the Kaposvár line, the HSL would allow rail services at Lake Balaton to be operationally isolated. They can then be restructured as a regional metro, more appropriate to an intensively developed resort zone. (The rail line on the north shore is not a through route, and can easily be isolated for local traffic).
The south shore line should also carry a regional service between Székesfehérvár and Nagykanizsa, connecting with high-speed services at both these stations. With some high-speed services also stopping at Siófok, that would offer good rail access to Lake Balaton, from both east and west.