Train Protection and Warning System (TPWS)

TPWS was developed in the aftermath of the Slough and Ladbroke Grove accidents in the late 1990s, it enhances the functionality of the previous system, the Automatic Warning System (AWS), which had been fitted in various forms since the 1950s. The system interfaces between the lineside signals, the cab environment and the automatic air brake system, giving the driver audible and visual data based upon the colour of the signal aspect (or indeed the position of the semaphore arm in some areas of the UK network), preventing the passing of signals at red, ensuring adherence to speed limits approaching junctions or other restrictions, plus the more well known “bell” and “horn” sounds depending on the aspect of the signals being driven past. TPWS has itself evolved, and the current level of TPWS4 is now the minimum required for any new installation of TPWS on either a new vehicle or a heritage vehicle being put forward for main line operation. Our main line locomotives, 50007, 50044 and 50049 all have TPWS fitted, and 50031 also has the equipment fitted from its days operating on the main line in the late 1990s and early 2000s.