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Geofence technology is a solution against misplacement of ZKLs

27 September 2022

Dual Inventive introduces geofence technology for locating workforce safety devices, such as the Track Circuit Operating Device (TCOD). During Railcenter’s Rail Festival, on 28 September, will be the first opportunity for a demonstration of the international innovation that makes misplacements of TCOD’s a thing of the past.

Self-monitoring Track Circuit Operating Device

TCODs are used daily as a second layer of protection during work activities when the track is taken out of service. The TCOD creates a short-circuit in the track, and reports this section as occupied to the train protection system. This prevents collision hazards for track workers.

In the Netherlands, there are two categories of TCOD’s: namely those with and without a remotely switchable short-circuit connection. The remotely switchable self-monitoring TCODs (ZKL 3000 RC) are semi-permanently installed well in advance of the work at a suitable time. These can then be used again without entering the track. The so-called manual ZKL 3000 is installed in the track immediately prior to the work. Misplacements have proven to be a risk when using manual ZKLs.


The ZKL technology has the highest level of safety and it functions well, but due to increasing work pressure, manual ZKLs are regularly installed in other places in the track than intended. These are called misplacements. It also happens that a ZKL is installed on the wrong side of an electric separation weld or signal. The installer may make a mistake about the location or misinterpret the Workplace Extraction Drawing (WOT).

Due to insufficient available working hours, the installer is regularly under pressure, and therefore sometimes works too hastily and does not check sufficiently whether the ZKL has been placed at the planned location.

Collision Hazard

Every year, dozens of incidents are reported to Stichting railAlert, the actual number of misplacements of manual ZKLs may be higher. The track that has been taken out of service is then not properly protected against approaching trains, as a result of which it is not possible to work safely on the track.

This is not an issue with the remotely switchable ZKL 3000 RC from Dual Inventive; however, the internationally active technology company based in Brabant also wants manual ZKLs to work more safely. Forces have been joined with Tended from the United Kingdom in an attempt to avoid misplacements.


Tended has developed geofence technology that provides virtual parameters around a location that can be pre-set via an online platform, for example, based on the WOT. An accuracy of 14 millimetres is achieved with the help of a small, portable device including GPS.

The device indicates to the installer when he is at the planned location so that the workplace safety device, such as a ZKL, can be installed at exactly the right location in the track and is therefore within the pre-set virtual barrier. In addition, track workers can be warned via the portable device when they leave a safe zone or approach the border of an unsafe zone.

Lex van der Poel, CTO of Dual Inventive, says:

“With this international collaboration, we mitigate misplacements of ZKLs, create the basic idea for using a digital border guard and improve the safety of track workers.”

During the Rail Festival, Dual Inventive, also in collaboration with Railcenter, will present a new work zone application, including hardware (RSS 3000), for remotely switching work zones within train security. In the United Kingdom, this RSS 3000 is in the final phase of approval and can be used in conjunction with the ZKL 3000 RC for remotely switching work zones.

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