TMB 2025 Traverse Update

Case Study: The Mont Blanc Traverse Update

INTRODUCTION

Mont Blanc Tunnel (TMB) is a 11.6 km highway tunnel connecting Courmayeur, in the Italian region of Valle d’Aosta, to Chamonix, in the French department of Haute-Savoie. Built between 1957 and 1965, it is a strategic transalpine transport route for trade, tourism, and communication between Italy and France. Every year, over 1.5 million vehicles use the TMB to travel from Italy to France or vice versa. (Traffic statistics | Mont Blanc).

In order to ensure its regular use, the maintenance and safety of the Mont Blanc Tunnel are extremely important issues for Italy and France. Routine and extraordinary maintenance activities are carried out every year and involve numerous agencies and companies, which must operate in the same context but using completely different approaches and techniques. 

The need to standardize references, providing companies operating in the TMB, a series of known coordinate points inside the tunnel, led to the creation of the Mont Blanc Traverse.

HISTORY

The Mont Blanc Traverse Project was launched in 2016 with the aim of positioning approximately 600 points within the tunnel to be used as control points (200 planimetric control points and 400 altimetric control points). The Mont Blanc Tunnel Management and Maintenance Office has entrusted Studio Tecnico Goso with the task of creating the traverse and its subsequent maintenance.

Traverse Update of 2025

After the traverse was completed in 2016, Studio Tecnico Goso was also involved in maintenance and subsequent updating of the traverse, due to routine and extraordinary maintenance work inside the tunnel. In 2020, it was necessary to replace approximately 30 control points, while in 2025, approximately 40 pins, which had been removed or destroyed during work in the tunnel.

This case study concerns the updating of the 2025 traverse carried out by Studio Goso using a Stonex R180 robotic total station.

The use of a high-performance total station in terms of accuracy is a necessary condition for this type of survey. Surveys that are carried out in a complex environment, characterized by numerous interferences and disturbances due to construction sites and moving workers, and that must be performed quickly during the periodic and rare nighttime closures of the tunnel.

The Stonex R180 robotic total station was chosen by Studio Goso as the optimal solution in terms of precision, reliability, speed, and data stability.

The R180 is a highly accurate and fast Android Robotic Total Station. It features a rotation speed of 180°/sec and an EDM accuracy of 1 mm + 1 ppm in prism mode, with a range of up to 1000 m without a prism. The R180 is available in three versions, 0.5″, 1″ and 2″ second. For all models, the quietness and smoothness in prism searches and rotations are among the most observed and appreciated features.

Equipped with the Android operating system, the R180 has Cube-a as onboard software. This enables users to navigate online and interact with the touch screen in an easy and familiar way.

Following the traverse pattern visible in the image below, each point was measured several times in F1/F2 configuration from different positions. The high redundancy of data, necessary to ensure high-quality measurements and a robust solution from a statistic point of view, plus the high speed of automatic target centering/measurement, proved to be a key to the success of the project. Specifications completely satisfied by R180 robotic total station.

Example for station S26

Here below an example of R180 measurements in F1/F2 configuration of a control point from station S26. The same point was also measured from other station positions to ensure high-quality measurements and a robust solution from a statistic point of view.

CONCLUSION

The update of the TMB 2025 Traverse has proved essential in providing reliable and up-to-date data to all those working within this international infrastructure.

Precision and speed, fundamental aspects for this type of job, were achieved thanks to Stonex R180 robotic total station. A complete solution, that, with its flexibility, is able to satisfy every customer request and adapt to different survey conditions, maintaining a high level of measurement accuracy.

Precision, reliability, and speed: these are the keywords used by Studio Tecnico Goso to describe its experience with R180. Factors that made the difference in updating the traverse of the Mont Blanc Tunnel.

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This case study was made possible thanks to the work and support of:

Founded in 1964, Studio Tecnico Goso is a leading Italian technical firm engaged in the management and implementation of public/private works and large-scale topographic/cartographic surveys. The company, based in Savona (SV) (Liguria, Northern Italy), operates throughout Italy and has been responsible for the Mont Blanc Traverse and its maintenance since 2016 (https://studiogoso.it/).

The Gruppo Europeo di Interesse Economico del Traforo del Monte Bianco (GEIE-TMB), uniquely a management structure, was established at the same time as the implementation of the tunnel’s renovation and modernization program, which finished in 2002. It is a French Italian structure under Community law, which statutes were lodged by the ATMB (the concessionary company of the motorway on the French side of the tunnel) and the SITMB (the concessionary company of the motorway on the Italian side of the tunnel) on May 18th, 2000, at the Aosta Valley’s Chamber of Commerce. On 1 March 2022, its name was changed to Mont Blanc Tunnel – GEIE (TMB-GEIE). It has its registered office in Courmayeur, at the Italian tunnel entrance apron, and it has a well-established organization on French soil (https://www.tunnelmb.net/en-US).