Both Maastricht and Liège are built on the river Maas / Meuse, and they are only about 30 km apart. The Liège agglomeration has about 600 000 inhabitants, and the Maastricht urban region about 180 000. Language differences (Dutch and French) probably counteract proximity to some extent: the Netherlands borders directly on Wallonia here.
The railway between Maastricht and Liège was built in 1861, along the right (east) bank of the river Maas / Meuse. The river has a broad floodplain with escarpments on both sides, about 50 – 100 m above the plain.
The line in 1901, click to enlarge: base map from Uni Greifswald, with some German place names…
From Maastricht to Visé, the line is in this floodplain, and generally straight. South of Visé, the river runs alongside the eastern escarpment, leaving just enough space for motorway, road and railway. The line is sharply curved in places, at the food of a cliff. The transition between the two landscapes is at Visé Station itself, which is also the border station.
Click to enlarge: river Meuse, riverside road, motorway, and Visé station…
The line is double-track and electrified at 1500 V in the Netherlands, 3000 V in Belgium. The voltage changes at the edge of Maastricht. Belgian trains can run under reduced voltage into Maastricht station, but Dutch trains can not run at Belgian voltage. Originally, the line stayed on the right bank of the river, terminating at Longdoz Station, opposite the city centre. Trains now continue past the centre on a connecting line, and turn north again across the Meuse, into the main Liège-Guillemins station.
For a few years, the city of Maastricht promoted a “high-speed” service to Brussels. In fact it was simply a Belgian Interciy, extended from Liège Guillemins to Maastricht over the existing line. There was no high speed, and no upgrading of the infrastructure. That train now stops at Visé: there is also an hourly Maastricht – Liège regional service.
Conversion of the line to an urban-regional metro line was proposed here, as part of an urban-regional network around Liège. The line would be re-routed into the city centre, with a new 4-km line across the river at the Ile de Monsin. That is compatible with a high-speed line, but neither project is a precondition for the other.
There are two general options for a high-speed line south from Maastricht. Either the new line follows the existing right bank line to Liège, or it crosses the Maas / Meuse and the parallel Albert Canal, and enters Liège from the north. More precisely, it would enter Liège-Guillemins from the north-west, sharing the approach tracks through Ans with the old main line from Brussels, and the high-speed line Brussels – Aachen. That requires a long tunnel from the river valley to the junction with the approach line, much of it under the built-up area of Liège.
In both variants, the existing line south of Maastricht would be doubled to four tracks, and upgraded for high speeds. Inside Maastricht no high speeds are possible: there is a curve just south of the station, and another at Randwyck, 1400 m further. Just before Randwyck station, the proposed HSL Maastricht – Aachen would diverge, requiring reconstruction of the curve, and probably relocation of the station.
The remaining line to Visé consists of two straight sections, with a curve at Eijsden. There is enough room for four tracks, and most of the line is in open fields. At Eijsden, the line cuts the village in half, and a cut-and-cover tunnel is preferable. That can be combined with a new curve: the station itself would remain on the surface.
The options for crossing the Meuse and Albert Canal are limited. On the west bank south of Maastricht there are quarries, cement plants, a preserved fortress (Fort d’Ében-Émael), and a nature reserve on the escarpment (Thier de Lanaye). Closer to Liège, both banks are urbanised. The most open section of the valley floor is south of Visé, and the tunnel on the west bank would then start near Oupeye. To cross the valley at the best angle, the new line would need to curve south-west, requiring another tunnel under Visé. That might be connected to a bypass of Eijsden (brown on the map).
The distance would be about 35 km, and journey time should be reduced to 15 minutes or less. The exact alignment can only be determined by detailed studies. An earlier proposal here, an alignment along the A13 / E313 motorway, offers no advantages.
The alignment through Oupeye is largely determined by the location of Liège Guillemins station, and the approach tracks through Ans. The line, the oldest railway in Belgium, was built well south of the historic city centre, because following the valley at Ans avoided a steep drop into the Meuse valley. In fact, the line here was originally an inclined plane. The inconvenient location of the main station is the result.
The tunnel alignment shown is indicative only. It crosses a valley, with the Ans line on the southern flank, and if this was not an urbanised area, a bridge would be more logical. However, the valley is not too deep for a tunnel on the approximate alignment shown. (The tunnel would be close to a similar exit tunnel for the proposed HSL Liège – Hasselt, but to avoid an underground junction both should have separate portals and alignments).
A new high-speed line along the Maas / Meuse valley, parallel to the existing line, would also require new tunnels. South of Visé, the line is too curved for high speeds, and, the line is often squeezed between the old main road and the motorway. The only option is a flank tunnel, or a series of flank tunnels, starting at Visé itself. The main issue is the last section into Liège Guillemins, to replace the inconvenient approach line.
The line through Visé Station is curved and for that reason alone unsuitable. Because the town is built on higher ground, a tunnel can pass under the centre, shortening the route slightly. In principle the tunnel would be level, at about 55 m elevation, but it might dip to clear buildings near the portals. It would rejoin the line near Richelle, so it would be about 4 km long.
A second flank tunnel, about 9 km long, would start near Richelle and emerge from the escarpment at Jupille, just north of the Jupiler brewery. Again the line would be ‘level’ in principle: more accurately, it would match the gradient of the river. Construction would be simplified by access ‘from the side’, since the tunnel will be close to the road. As with all tunnels in this region, construction must take account of former coal mining – shafts, galleries, and subsidence.
A single flank tunnel of about 14 km is also possible, but even in that case a junction with the old line at Richelle might be desirable. (At that point, the tunnel would be just behind the escarpment).
From Jupille to the railway yard at Bressoux, the line is straight. After that, it is double-track but curved: no alternative alignment is available since it cuts through residential areas. The HSL would require another tunnel, into the city centre.
One possibility is that the HSL would emerge from tunnel north of Jupille, and run parallel to the proposed Monsin link line. This link is intended to connect Line 40 to Line 34 across the Meuse valley, to create a regional metro line from Maastricht into central Liège.
On the opposite bank, the HSL would dive into the hillside in tunnel, and turn to run parallel to Line 34. This last section would not allow high speeds, but it is only 3 km long. It would run under the Parc de la Citadelle, and terminate at an underground station, alongside Liège-Palais Sation. This would allow easy transfer to a regional metro, at a station just north of the historic city centre..
Combined with the flank tunnels, this would shorten the route from Maatsricht to central Liége to just under 30 km. The last tunnel can be extended to Liége-Guillemins station, for interchange with the Brussels – Aachen high-speed route, and with Intercity services. The junction would be relatively close to the station, where the A602 motorway was built on pillars above the railway line, making it impossible to modify. Relocation of the motorway seems a precondition for this junction – and for doubling of the line, which carries all traffic west from Liège.
This is only one of several possible tunnel alignments. The shortest route is simply a tunnel under Outremeuse, from Bressoux to the centre, but there is no good site for a station, so it would be entirely underground. The station would have deep platforms, since the line must pass under the river, and the city centre is on higher ground. This route is also more difficult to connect to Liége-Guillemins station. The possible tunnel alignments into the city centre are not considered further here.