Work progresses on the RER network around Brussels

Works in progress in Ottignies, south of Brussels Frédéric de Kemmeter

Work on the Regional Express Network (Réseau Express Régional or RER) is progressing on the two lines to the south-east of Brussels. Ottignies station is undergoing a complete reconfiguration of its facilities, while the L124 line to Nivelles is undergoing major works.

The local and suburban network, known as the “Réseau S” in Belgium, is designed to facilitate and increase traffic on trains with frequent stops, such as the S-Bahn in Germany or the RER in Paris. While some lines around Brussels have not undergone many changes, most have been extended to four tracks, as is the case on lines L96 to Halle, L36 to Leuven and L50A to Denderleeuw (and Ghent).

Work remains to be completed on two other lines: the L161 to Ottignies (and Namur) and the L124 to Nivelles (and Charleroi). These two lines cross hilly terrain, which has required more civil engineering work. This work is almost complete on the L161 line to Ottignies but is still in progress on the L124 line to Nivelles.

Facilitating traffic

It is not possible to offer a frequent local train service if there is a mix of fast intercity trains. The two types of traffic therefore need to be separated by doubling the width of the lines from 2 to 4 tracks. Eventually, this will allow local traffic to run on the 2 adjacent tracks, while fast trains will occupy the central tracks.

Four-tracking was not always easy because of the extensive urbanisation of the south-east of Brussels, where houses and gardens are located virtually all along the tracks, both towards Ottignies and Nivelles.

In some cases, trenches had to be widened and straight concrete walls built. In other cases, embankments had to be widened and, here too, walls had to be built to hold them in place. All the bridges had to be widened to make way for four lanes, which was also sometimes difficult because of the highly urbanised environment in some places.

BrusselsA new Arc de Triomphe in Lillois, on the L124 line (photo Infrabel) 

As Infrabel is obliged to maintain SNCB traffic throughout the year, the infrastructure manager has to plan its worksites using a complex phasing system. Several times a year, the law allows a line to be completely shut down, but only at weekends.

L161 to Ottignies

On the L161 line to Ottignies, the major civil engineering works are almost complete. What remains to be done, however, is to lay the track, the catenary and the new signalling, and above all to reposition the two existing tracks in their correct position, which is a complex task.

To the south of Ottignies, a 2.5km worksite as far as the Louvain-la-Neuve’s junction was inaugurated at the end of 2023. With its 4 tracks, this is the first completed kilometres of the S network in the south-east of Brussels.

At the same time, Infrabel is completely reworking the Ottignies station’s tracks, with a completely revised layout and lengthened platforms. A new configuration of the station tracks – and therefore of the platforms – has been studied and is the subject of a major phasing programme that will last several years. Old yard tracks, which had become redundant over time, are being replaced by the new station tracks.

L124 to Nivelles

There are still major civil engineering works to be completed on this line. Some sections of the line are already four-track, and a major curve at the entrance to Nivelles is being reconfigured to increase speed, thereby improving traffic flow.

Further reading

Author: Frédéric de Kemmeter

Frédéric de Kemmeter is signalling technician and railway policy observer.

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