A high-speed line (HSL) from Maribor to Zagreb would connect to the proposed HSL Wien – Maribor, and the existing line from Graz. The Zagreb HSL would share about 20 km of line, with the earlier proposed HSL Maribor – Ptuj – Koprivnica.
There never was a main rail line into Zagreb from the north. From Maribor, the easiest route is via the Ljubljana line to Zdani Most, and from there via the Ljubljana – Zagreb line. However, there is a new motorway: the A2 in Croatia is complete, the final section of the A4 in Slovenia (south of Draženci) is due for completion in 2013. There are no current plans for a new north-south rail line, although is an obvious addition to the existing network, and has been proposed earlier. The Croatian rail network is of poor quality: even the European corridor V and corridor X are mainly single-track. The only planned new line, Zagreb – Rijeka, has been delayed.
At the border, the motorway crosses the Macelj ridge, the main topographic obstacle. From Djurmanec, it follows the existing rail lines, along river valleys: Croatian local line L103 to Zabok, regional line R201 to Zaprešić 15 km east of Zagreb. These are local lines built to low standards, and not suitable for major upgrading.
Krapina Station: CC3 license by Kiki273…
Any new line Maribor – Zagreb would use this corridor, along the river valleys south of Macelj, and parallel to the motorway. There is no logical alternative. The alignment excludes very high line speeds (current maximum line speeds are 350 km/h for lines across flat terrain). Line speeds of 200 km/h would be reasonable, for the central section of the Maribor – Zagreb line.
The existing main line out of Maribor runs almost due south, to Pragersko. The HSL toward Zagreb and Ptuj would turn south-east, like the A4. However the motorway starts near the airport, to make a junction with the older Ljubljana motorway. The HSL could run further east, through the flat Drava Polje. It would pass east of Rogoza, and then run parallel to the Drava diversion canal. At Prepolje, the alignment would join the A4.
An alternative alignment (in black) would leave the main line further south, close to Rogoza. It would pass Maribor airport, and then turn to join the A4. This alignment could pass directly in front of the airport terminal, but there is no reason for a station. Like many other regional airports in Europe, Maribor airport is uneconomic, and will remain so. The terminal is designed for 600 000 passengers per year, but is currently handling only 3% of that.
The HSL toward Koprivnica would turn off, as the new line crossed the existing line (into Ptuj). The Zagreb HSL would continue alongside the A4 motorway. About 6 km further, at Jurovci, the flat plain ends abruptly, and the Haloze hills begin.
From here, the new line would share restricted space in valleys, with the old road and the motorway. As the motorway reaches the Macelj ridge, it follows narrow stream valleys – they had to be widened in places, to fit the road. The curving motorway alignment here is also incompatible with high speeds.
The only option for the HSL is a base tunnel, about 5 km long, with a southern portal near Djurmanec. However, the valley there is still narrow and winding. Like the motorway, several shorter tunnels would be needed between Djurmanec and Krapina. The alignments shown are indicative only, local conditions would determine the exact alignment on this section.
Click to enlarge…
The A2 motorway bypasses Krapina along an adjoining valley, using several tunnel sections. The HSL might use a similar option, but a tunnel connection to the existing station might be preferable. Some trains on the HSL could serve stations at Krapina (population 5000) and Zabok (population 9000), so long as there are through tracks for non-stop trains. The HSL could also be used by inter-regional trains on a re-routed Zagreb – Varaždin line.
South of Krapina, the rail alignment is straighter. However, neither the rail line, nor the motorway, is fully suited for a high-speed alignment. The HSL would need to switch between the two, to minimize curves, and maximize straight sections. South of Zabok, the valley (River Krapina) is wider, so this strategy is easier.
Click to enlarge: existing rail line highlighted in white, HSL alignment next to rail line or motorway, alternative alignment in yellow…
At Zaprešić, the Krapina joins the Sava, and the rail line joins the line from Ljubljana. There is a sharp curve here, as the river passes the edge of the hills: the railway and the old road are squeezed into the narrow strip between them. The motorway avoids this restriction by crossing the Sava and the Krapina: the HSL would use a similar solution, crossing the Sava twice.
After this curve, the line enters the built-up area of Zagreb, 12 km from the main station. The existing line would need reconstruction and quadrupling, but it is almost straight. There is one S-curve just before the station, followed by a flat junction with the line from Rijeka. Zagreb central station (Glavni Kolodvor) itself is relatively small, but there is some room for extra platforms.
Click to enlarge…
The line would be about 108 km long, and journey time between the two cities would be cut to 45-50 minutes. At Zagreb, the new line would connect to the officially planned HSL to Rijeka, and to a HSL parallel to the existing main line to Beograd (Belgrade). It would also connect to regional and urban services around Zagreb. On the new alignment, Zabok would be about 40 km from Zagreb, and Krapina 55 km, with a potential for fast regional services. No other settlements on the route is large enough to justify a station – not even for limited numbers of trains.