Largest Route Relay Interlocking (RRI) installation

Largest Route Relay Interlocking (RRI) installation
Who
Indian Railways, Delhi Main Sation
Where
Delhi Main Station,
When
February 1999
The largest Route Relay Interlocking system is at Delhi Main Station, India.
The system uses 11,000 relays allowing up to 1122 signalled movements. Route Relay Interlocking is provided for major junctions and yards where large numbers of train movements are required. Interlocking is a system for checking the route the a train is going to take before clearing the signal and  prevents the clearing of a signal until the route is clear. It eliminates human error and ensures safety in train operations. Delhi Main Station is also known
as Old Delhi Station.