Deutsche Bahn

Provision of a device to prevent the over-speeding of trams

DB ESG wins a contract from Transport for London for the provision of a device that physically prevents the over-speeding of Trams.

(Derby, 17.January 2019) DB ESG is contracted to develop, supply, install and commission a physical prevention of overspeeding  (PPOS) device for the Croydon tram fleet. This protection system will operate independently of the other tram monitoring systems and will stop a vehicle if it is found to be travelling at excessive speed within pre-defined locations, with the flexibility to be introduced on other parts of the network.

DB ESG has sub-contracted Sella Controls, who will provide the equipment necessary for the PPOS system. The system consists of a PPOS controller fitted into the tram, together with Sella’s proven Tracklink III system, which communicates data from the rail infrastructure to the tram. The Tracklink III system consists of track beacons and an on-tram reader.

In the event of a tram overspeeding in a speed restricted area, the PPOS controller will interrupt the power to the PPOS safety relay. This will result in full service brake application and will bring that vehicle to a controlled stand-still.


Commenting on this order, Nick Goodhand, Managing Director at DB ESG, said: “This reliable protection system will not impact on the normal service delivery or performance of the tram network. It also has the added advantage of being flexible and adaptable, allowing the inclusion of tempory speed restrictions and further defined locations to be permanently protected in the future.”

Mark Davis, TfL's General Manager of London Trams added: "Awarding the contract for a new automatic braking system is a first for trams in the UK, and not only will it improve safety for customers in London, but we hope it will lead the way for other tram operators across the country.”


Roof mounted, Wi-Fi/3G/4G antennas will advise the operational controllers of any critical events. Communication will be via the public, mobile data network during tram operation.  A new dedicated Wi-Fi system will also be installed at the depot. The Wi-Fi system will be dedicated to PPOS and will communicate with a PPOS work station.

Iain Wilkinson, Business Development Manager at Sella Controls said:  “This project gives us the opportunity to implement our well proven products from other rail projects and apply it to this new tram overspeed application.”