The asset management of railway tracks is mainly driven by the analysis of track geometry parameters. Data are often collected by dedicated inspection vehicles and track maintenance procedures are based on historical experience-based thresholds. Over the last years, new approaches to monitor the track quality have appeared: several networks considered acceleration measurements (dynamic measurements) as a useful means to get interesting information on the network condition. Although the use of accelerometers presents undeniable advantages, for instance the reduced cost and the easy portability, its implementation in industrial maintenance processes is not trivial. Mainly, measured accelerations depend on very various factors that must be controlled in order to produce consistent thresholds for the maintainer.

That is why, at the end of 2018 SNCF Réseau (Ms Agathe Momas and Mr Danilo Sorrentino) decided to work with UIC (represented by Infrastructure advisors Mr David Mirayo and Mr David Villalmanzo Resusta) in order to set up a team for an international project to tackle this topic. After a first plenary meeting held in Paris in February 2019, where 12 international companies showed their interest, new companies coming from around the world joined this challenging project. Today, the UIC Harmotrack project (Harmonization of track quality description and assessment) is an international project bringing together more than 60 international railway experts from 28 different companies to study the use of accelerometers for dynamic monitoring of the tracks.

The first achieved goal for this project was the finalisation of an international benchmark report on the use of dynamic measurements. This interesting document made it easier to understand how the companies use accelerometers: current normative uses of dynamic measurements, values of the thresholds, technical specifications, localisation methods etc.
After this important milestone, project members understood that the harmonisation of measurement practices was important.

Thus, nowadays the project, led by SNCF Réseau (Mr Danilo Sorrentino and Ms Solène Estival), is organised into three sub-working groups (SWGs) listed below:

SWG1: Determination of thresholds for accelerations - Group leader Mr Danilo Sorrentino and Ms Solène Estival (SNCF Réseau).

• This group covers a wide panel of problems regarding the relation between acceleration measurements and safety, comfort, normative control of the rail and maintenance interventions. The original aim of this group is to recommend a method for developing sensible thresholds on accelerations that truly relate to the safety and comfort of the rail. This concern comes from the observation that there exists a variety of thresholds that are sometimes too permissive; originate from remote measurement campaigns and rarely account for the vehicle specificities.
• This group is split in two groups:
  • SWG1-A to study the correlation between measured forces and accelerations (Group leader - Mr Fatih Ünlü SBB CFF FFS);
  • SGW1-B to study the correlation between measured track geometry defects and accelerations (Group leader - Mr Danilo Sorrentino and Ms Solène Estival SNCF Réseau).

SWG2: Optimal use of axle box accelerations for the detection of short length defects - Group leader Mr Stanislaw Banaszak (SBB CFF FFS).

• The main topic of interest for the group is the detection of short length defects of the rail using axle box accelerations (ABA). The aim is to compare detection capabilities between accelerometers and other regularly employed detection devices (video inspection, ultrasonic, eddy-current), in order to know the extent of information that can be drawn from ABA measurements.

SWG3: Use of innovative and cheap devices – Group Leader Mr Franck Dadié (SNCF Réseau).

• This group focuses on the comparison of cheap measurement devices for car body accelerations with traditional measurement devices. In particular, members want to determine if built-in accelerometers from smartphones can provide signals that are reliable enough and which could replace heavier and more expensive devices.

This international project, which is a very enriching experience for all the project members, will lead the companies to define future international technical specifications (or recommendations) on the use of accelerometers for the track monitoring. The project is expected to end at the beginning of 2022 and the next plenary meeting is scheduled for October 2020.