Deutsche Bahn

Turnkey supply of a physical prevention of overspeeding (PPOS) system for London Trams network

(Derby, 18. October 2021) DB ESG was contracted to develop, design, install and commission the PPOS system for Transport of London.

A light rail network is operated around the Croydon area that is owned by London Trams (a subsidiary of Transport for London). There are several areas of the tram route that are subject to speed restrictions because of the curvature of the track. London Trams identified a need for a protection system of last resort that was independent of other tram monitoring systems and had a safety integrity of SIL2.

The PPOS system would automatically bring a tram to a controlled stop via a full-service brake application if the vehicle speed was found to exceed the speed limit set at pre-determined sections.

DB ESG was contracted to develop, design, install and commission the PPOS system.

DB ESG sub-contracted Sella Controls to provide the equipment consisting of:

  • Tracklink III beacons mounted on the track. 
  • Tracklink III readers mounted to the vehicle underframes.
  • PPOS controllers within the tram, which report data to a control room workstation.

In addition, the trams required roof mounted, 3G/4G antennae to facilitate direct communication to the control room located workstation, as well as PPOS dedicated WiFi for daily data download.
The London Tram Fleet consists of 36 vehicles of two main types – 12 Stadler Variotram vehicles and 24 Bombardier CR4000 vehicles.

Work Undertaken by DB ESG (2019-2021)

  • Vehicle and depot surveys.
  • Detailed designs were created for both vehicle types, with detailed design reports produced.
  • Human Factors assessments were undertaken to cover all cab components.
  • Modification procedures, detailing the installation of all new equipment, wiring and hardware, and changes to existing vehicle components, system testing and commissioning, were created.
  • Creation of an environment management plan to identify any environmental impact and outline the roles and responsibilities of all DB ESG and sub-contractor staff in relation to environmental management.
  • Installation, operation and maintenance manuals were produced for the PPOS system and each component.
  • Production of assurance documentation and provision of independent safety assessment of the developed system to demonstrate compliance with SIL2.
  • Material supply – DB ESG procured and supplied all necessary materials.
  • Fully managed the fleet and track-based equipment installations.
  • Training provided for all elements of the system.
  • Testing and commissioning of the system, including static and dynamic testing at low and high speed.