Final inspection of Lötschberg Base Tunnel



BLS AlpTransit AG

Task definition

Image and profile recording as proof of clearance. Clarification of whether the current profile is compatible with the future “Shuttle Profile”.


  • Recording with the TS3
  • Total length 51 km
Source: BLS

The project in detail

After an eight-year construction period, the Lötschberg Base Tunnel was opened in a ceremony held on 15th June 2007.
At 34.5 km, it was then the longest tunnel in Switzerland, the third-longest in the world, and an important part of the New Rail Link through the Alps (NRLA) construction project in Switzerland.
It runs from the Bernese Oberland to the Valais and is part of a broader concept which aims to reduce road traffic and promote rail transport in Switzerland.
The contracting authority, BLS AlpTransit AG, required several inspections to clarify whether specific clearance values and distances had been observed, e.g. between the current collectors on vehicles and fixed equipment.


As a basis for the profile checks, a full-surface scanner recording of all tunnel sections was made at a high resolution (10,000 pixels per 360° scan).

The SPACETEC TS3 tunnel scanner was used in combination with the SPACETEC rail-road vehicle. Four shifts were made available for the measuring in the weeks prior to the opening of the tunnel.

Source: Siemens


Using the scanner recordings, it was possible to carry out the individual profile checks within a short time. The owner, BLS AG, also has comprehensive technical documentation, which will be an important source of information for future tunnel inspections and assessing any structural changes.

The most important test was to confirm adherence to the minimum permissible distances between vehicles and the tunnel, including fixtures, as required by the regulatory authority for railways.

Plans exist to drive specialised vehicles, the Lötschberg Shuttle, through the tunnel at a later date. One inspection was carried out in order to establish whether any fixtures would protrude into the required clearance profile for these larger vehicles and would therefore require modification.

The total length of the LBT’s tunnel tubes is over 60 km. A huge number of fixtures which had to be inspected. It would have been extremely labour-intensive and time-consuming to carry out control measurements on site for each individual item.

The use of the SPACETEC TS3, on the other hand, has proven to be highly efficient, allowing the whole tunnel system to be scanned in just 4 days.

The SPACETEC analysis program TuView was used for the various clearances. This makes it simple to detect any breaches of the established clearance tolerances, as they are highlighted in colour on the scan image.

Suspicious areas identified in this way were then inspected in more detail using TuView’s analysis tools, enabling the cause to be determined with ease. This provided the operator with valuable information, allowing them to take remedial action.

The following screenshots demonstrate the various ways of visualising the results of the clearance profile inspection — full-surface clearance profile mapping as a development or in detail in TuView, or a 3D passage through the tunnel in TuDrive.


In the clearance profile mapping shown here, green indicates that the object is close to the boundary line but the required distances are observed.


During retensioning, components can approach or protrude into the area which is to be kept clear. This shows the guide pulley of a retensioning device.


In the clearance profile mapping shown here, green indicates that the object is close to the boundary line but the required distances are observed.