Non-Interlocked… and Stranded

By Sridhar Joshi & Khalid Kagzi

Rakesh was at his wit’s end as to how to reach home; the train for which he had booked a ticket about 90 days in advance was terminated 140 km short of its destination on a Sunday. He had two options: take it or leave it.

An innocuous SMS from Indian Railways (IR) attributed this termination to non-interlocking (NI) works near his hometown.

Non-interlocking work refers to the dismantling of existing signalling equipment (not necessarily old technology) for commissioning a new signaling system at any station or section of railways.

Post dismantling, trains are received, held and dispatched at a station using the manual system of showing flags and setting paths for trains using clamped rails.

During this period, the trains are allowed to run on what is called paper authority – the station masters manning various posts issue written permissions for a train to cross a section of the track.

The manual system can at best be 50 per cent efficient as that of the interlocked system. Meaning: A station which could earlier handle 200 trains a day can at best manage to pass 100 a day under the manual system. Also, the manual system necessitates receiving trains at slow speeds of about 10 kmph, thus reducing a station’s capacity to handle trains.

This leads to delays, diversions, short-terminations and short origination, and regulation of trains, affecting schedules in the short term.

Necessary evil, long term benefits

IR cannot avoid NI in most cases if they have to commission a line, modify or augment the layout of a station. While passengers may face several difficulties during NI period, the long-term benefits – increase in carrying capacity, speed, and safety – far outweigh the temporary trouble.

List of Non-interlocking works on IR since January 2019

NERAunrihar JnApril 12-15
NCRMaripatApril 6-14
CRBhusavalApril 6-18
ECRKurhni-Goraul section and Bhagwan stn of Sonpur divisionApril 7- April 17
ECRAthmalgola in Danapur divisionApril 6-April 18
SRArakkonam JnApril 5-14
NRLucknow- -Raebareli-Pratapgarh -VaranasiMarch 15-19
NRDelhi -Meerut City-SaharanpurFeb 27- March 10
NCRParauna-Ait-Bhua of Jhansi DivisionFeb 19- March 1
SECRPendra Road- AnuppurFeb 11- March 5
ECRPaimar on Kiul -Gaya lineFeb 10-Feb 27
WCRHoshangabadJan31- Feb 11
ERSealdah-RanaghatFebruary 8- 10
SWRBengaluru CanttFeb 9 -10
ECRSaharsaJan 30- Feb 5
SECRChampaJan 7- Feb 2
ECRSoneNagarJan 16- Jan 26
NERManduadihDec 27 2018-Jan 13 2019

Pre-NI works

Before any NI is sanctioned, a team of officers examine the procedure to ensure maximum work gets completed in minimum time.

So, how do trains work when there are no signals?

The entire station that comes under NI work is divided into segments from the home signal (signal at station entry) on one end to the last stop signal (signal at station exit), also known as the advance starter.

Each segment has a goomty (a hut) erected with facilities like furniture, water, statutory registers, point clamps and locks. Each is manned by a minimum of one station master and one pointsman. Goomties controlling multiple points and crossings may have more staff. Platforms could also have goomties. [Point is a location from where a track veers away to join another. The track veering away is called a turnout]

Illustration from

All the unwanted points and crossings are removed and new ones are inserted. Normally, points are driven by electric motors. During NI working, these motors are disabled and do not work.

Hence the points are manually “cranked” to the required position and then a clamp is applied and locked to ensure that no unauthorised person can alter the position of the points.

The key to the clamp remains in the custody of the SM who is in charge of the area. Trains are moved at extremely restricted speed as low as 10 kmph. Once all the points and crossings are in place, these are linked to the Route Relay Interlocking (RRI)* Panel at a central cabin for the station.

[The Route Relay Interlocking is a system of signalling which ensures that required route for the movement of a train can be completed just by pressing a few buttons on a panel. In addition the system also ensures that the safe conditions for setting the route are available. While ensuring safe conditions, the system also ensures that another route that is conflicting with one set route is not allowed]

Planning for NI

Planning is super-meticulously detailed before NI work commences at a station.

Step 1 Request from all departments concerned: engineering. electrical, traffic etc detailing manpower required, nature of work, volume of work, number of days and hours required, details of speed restrictions, line closures machinery requirements, etc. Usually surplus resources are called for including manpower.

Step 2 Site inspection is carried out to confirm the repercussions for major works such as yard remodeling, subway construction, launch of girders for bridges etc.

Step 3 The traffic department studies repercussions to existing train time tables and suggests alternatives to cause minimum inconvenience to passengers.

Step 4 A detailed report is made consisting of location of goomties, their staffing, requisitioning of spare personnel and stand by machinery. Amendments if any are studied in detail by the department requesting the block for their impact on the revised date.

Step 5 The block is granted by the competent authority (division//zone/railway board) based on the duration, impact on train operations especially the number of train diversions, cancellations, short termination and regulation and their impact on the neighbouring railway zones.

 Step 6 A Temporary Working Rule or Temporary Working Order for the station is made from the detailed report and issued to all officials concerned thereby establishing a clear chain of command.

Step 7 The pre-NI works may be split into several small blocks of work in which isolated works are carried out like fixing of point machines(the motors which operated the track changing switches),shifting of working cables, testing of the interlocking system, etc. This system of Pre-NI ensures that the actual NI period is considerably reduced and overall effect on the running of trains is minimal.

NI Phase

A temporary public address system is used to announce impending train movements to all field staff (who are also provided walkie-talkie sets). All goomties are connected via telephonic hotlines.

If the NI period stretches into the night, then flood lights are used to ensure uninterrupted work.

The signal department prepares a consolidated sheet of the changes implemented in the yard. This is provided to drivers of trains approaching the NI site to keep them informed of the number and location of signals –both dismantled and newly commissioned.

A blanket speed restriction is imposed in the whole yard with unnecessary movements such as shunting and locomotive changes being curtailed/shifted elsewhere.

Movement of freights is either completely stopped or is severely curtailed. Light engines /passenger and goods rake s are not stabled in the yard during the NI period.

Any live shunting engines are kept in an earmarked line until required.

As far as possible, all movements are handled over the main lines. Any diversion to other lines is allowed only if absolutely necessary. This ensures that the points/clamps need not be changed for subsequent movements.

Advance intimation is given to all railway zones whose trains pass through the station or section. Moreover, intimation is to the Passenger Reservation System to ensure that the delays, re-routing and cancellations are correctly reflected.

Typically, during the NI phase, the train traffic over the section is very low and IR takes advantage by operating ‘shadow blocks’. Shadow blocks are traffic blocks (where traffic is stopped) granted in other stations to undertake various kinds of infrastructure maintenance.

Time over-run during an NI is usually accounted for and accepted.NI works usually avoid rainy season, major festivals and local observances.

Knowing all this does not put an end to Rakesh’s hardships as a passenger in the crossfire of a block, but will soften the blow as soon as he sees the SMS curtailing his train’s destination.

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