London Underground contractor invents the first permanent fail-safe device for detecting live currents

Tube Lines has developed a permanent trackside device to protect engineers from live currents when they are working on the Underground.

The permanent current rail indicator device (P-CRID) is a trackside fixture that allows engineers working at night to check the live rail is turned off while waiting from a place of safety.

Around 5,000 people work to maintain and upgrade the Underground every night, and work cannot start before passenger trains are taken out of service and the track current is off.

Currently engineers rely on certified Protection Masters who each use a handheld current rail indicator device (CRID) to check the 630 voltage traction current is switched off.

The contractor, which is rebuilding the Jubilee, Northern and Piccadilly lines, said the design is the first to test fail-safe.

It also constantly monitors its own condition and connections and in the event of a disconnection or internal fault it will warn workers not to go onto the track.

Tube Lines said the CRID can be easily damaged and needs to be overhauled each year, whereas the P-CRID has a design life of more than 20 years and the battery only needs changing every two years.

Gary Downie, Delivery Manager of Lifts, Escalators, Structures and Depots for Tube Lines who managed the P-CRID project said: “Our P-CRID innovation represents a massive step-change improvement to the way Tube engineers are protected when working on the track. This is one of the biggest safety improvements made in the industry for decades.”

The unit has been installed at more than 300 track access locations, and will be fully implemented on Tube Lines’ lines over the next two months.