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Rail Infrastructure Clearance Management

The aim of INFRACLEAR is to allow optimum use of the infrastructures ‘track clearance’ by means of an innovative approach for track gauging using operational monitoring technology and thus contributing towards increasing the capacity and safety of the infrastructure.

Tags: Rail


In the UK, Laser Rail is in the process of delivering a track clearance measuring system to Network Rail. The national gauging project (NGP) aims to upgrade the measuring platform by using modern ‘off-the-shelf’ equipment like a high-speed rotating laser.

In Germany, the consortium, made up of Metronom Automation, FTI Engineering Network and Fraunhofer Institute Physical Measurement Techniques, has developed a high-speed train-borne measuring system, THELIX, which aims to deliver clearance profiles at cyberspeed.

In France, this train is to be operated by Deutsche Bahn. OBSERVEUR (the last generation of PHOTOPROFIL 1 and 2) is at the acceptance phase from SNCF for operating inspections of civil engineering at between 5 and 120 Km/h

In Italy, FS is currently developing a new measuring vehicle from MERMEC, which aims to deliver clearance measurements.


The current technologies used for infrastructure gauging purposes are very simple:

  • the most common checking system is made of a piece of wood, shaped like a train, which is expected to run through the tunnels, and the gauging process consists of checking the breakage of that piece of wood after it has travelled over several kilometres of track: it is only a go/no-go process, with very poor measurement or location capability.
  • a more recent system is composed of a rotating laser scanner, mounted either on a lorry or a road-railer, and run at just a few kilometres per hour. These systems may provide digital processing of the clearance, but the track must be closed before starting a measuring run.
  • some other countries, like France, are operating a measuring wagon, travelling in the range of 5-10 km/h. Such a low running speed has the same drawback as manual inspection systems: the track has to be closed during the measurement run.

The objective of the present research work is to make it possible to run on the track to be inspected at a commercial running speed. This process would allow the clearance to be checked without stopping the commercial trains. The expected gain is very advantageous from a commercial and financial point of view of the global management of the infrastructure.

Description of work

The INFRACLEAR clearance sensor under development is based on laser sheet triangulation profiling techniques. It integrates the following technologies:

  • a laser sheet projector, with a fan angle close to 270° perpendicular to the axis of the track. The laser power is an 18 W continuous wave solid-state laser, with specific spreading optics
  • one set of high-speed and high-resolution cameras, installed separately from the laser, pan for clearance measurement
  • geometric stability of this arrangement is ensured by the implementation of a global rigid metallic frame supporting all the cabinets, including the lasers or sensors
  • a running track reference, based on the inertial principle, is provided by additional cabinets, including lasers, cameras and inertial sensor, which is attached under the main frame and looking closely towards the rail
  • the whole sensor frame, with all the sensor cabinets and the computers will be installed in a ‘comfortable’ container, well protected against the outside environment
  • the measuring container has to be mounted on a classical freight wagon, and fixed on it with the usual locks. This solution makes it possible to put the measuring container on any wagon, so it can be run on a specific track gauge.

This system will be composed of three sub-systems namely:

  • a measurement device, including a train-borne sensor and the measuring car
  • a processing device associated with an expert system to provide conditional maintenance programmes
  • a simulation tool making it possible to determine clear and safe ‘European routes’ for a given train gauge over borders.


The performance of the inspection device is summarised below:

  • an inspection should be carried out at least once a year on the entire railway network (inspection of single tracks is expected to be performed in a single operation)
  • the targeted measuring speed objective during inspection is 120 to 140 km/h.
  • the accuracy of the system must allow for detection of obstacles with a minimum thickness of 20 mm, i.e. 0.5 ms passing time in front of the sensor when the train is running at 140 km/h.
  • the dimension and space requirements of the device will be designed so that they are accepted on the different networks.

The potential market impact foreseen is based on the following forecasted costs:

  • Operation rate (with no operator): €5 000 per day
  • Stand-by rate: €500 per day
  • Modulate/demodulate rate: lump sum to be defined from time to time.