LUDHIANA: When the government is planning to induct bullet trains in the country, Railways is still relying on the 50-year-old methodology of using detonators to operate trains during fog.
Contents
In the Ferozepur division of the Northern Railways, officials deploy fog-signal men, who are trained to install detonators on the railway tracks near all stations, in a bid to alert the locomotive pilot.
Detonators are the small crackers that are installed 270 metres before the home signal, which is around 200 metres away from the station.
Absence of automatic block signalling, which costs over Rs 60 lakh as per estimates, is taking a toll on the frequency of the trains in the winter season.
Divisional operating manager Ashok Salaria says, “When a train is about to arrive, fog-signal men fix two detonators on the railway tracks at a distance of 10 metres — around 270 metres before the home signal — and then stand at a distance of 40 metres from the place where the detonators are installed.
When the train runs over the detonator, it produces a loud hiss. This alerts the locomotive pilot that the station is about to arrive and the train is around 270 metres away from the home signal. Following the alarm, the drivers adjust the speed accordingly.”
He adds, “But detonators are installed only when station master or any other competent railway official declare the low visibility due to fog or smog through visibility test object.
How railways declares poor visibility due to fog
Railways is not dependent on the weather department to declare the poor visibility due to fog, says Salaria.
“It follows Visibility Test Object (VTO), in which a railway official draws a yellow-coloured circle of one-metre diameter on the platform, 180 metres away from the home signal,” he adds.
A competent railway official such as station superintendent, station master or any other authorised functionary then stands on that circle and sees the signal. “If he is able to see the signal clearly, then the conditions are normal. But if he cannot spot the signal, he declares poor visibility due to fog and then asks the fog-signal men to install detonators and it continues until the official doesn’t see the signal properly from 180-metre distance,” Salaria says.
Lack of automatic block signalling
This season, Railways also reduced the number of trains from operating on the tracks and even limited the train speed up to 60km per hour during fog. This caused considerable delays and cancellations on daily basis resulting in harassment faced by hundreds of passengers.
When interacted with some locomotive pilots, it was informed that in other divisions, the Railways have installed huge reflectors (sigma) near the signal stand which help in locating the signals.
The practice of using detonators has stopped in the rest of the divisions, but is still being used in the Ferozepur division.
“Moreover, Ferozepur division lacks automatic block signals (ABS) which are installed at other divisions of the Northern Railways. Around three block signals are installed at specific distance between the two stations and it helps in managing multiple trains on one track. It also helps to reduce the delay in running status,” a loco pilot said. Since this division lacks ABS, one train is operated at a time and another train is departed only after the first train reaches the other nearest station, thus causing delays.
Fog safety device
Railways has also provided the train drivers with fog-safety devices, attached with a global positioning system (GPS).
Fog-safety device is an audio-visual instrument enabled with GPS. “It indicates us about the positioning of the stations. It navigates the train route and indicates when the station is about to come, then we look out of the window to see the signal whether it is green or red,” said another locomotive pilot.
Yes, many national railways still use detonators—also called fog signals or torpedoes—to alert train drivers during low-visibility situations like fog. Here’s how they work and why they’re still in use:
🔧 What Are Detonators and How Are They Used?
- A detonator is a small, disc‑shaped explosive device placed on the rail head, secured with metal clasps. When a train passes over it, it emits a loud bang audible to the train crew
- In India, two detonators are typically placed about 270 m before the home signal when visibility is severely impeded—as assessed using a Visibility Test Object (VTO) at ~180 m
- UK railways similarly deploy fog-signal men to place detonators to repeat distant signal aspects when fog obscures sightlines—I.e., physical and audible redundancy in fog rule procedures
📍 Why Continue Using Them Today?
India
- In winter, especially in fog-prone regions (eastern/northern zones), railways still rely on detonators as fog safety measures, even as newer tech exists
- Alternatives like Fog Safety Devices (FSDs) or GPS-based systems have been deployed but seen as unreliable or unpopular due to technical issues, over-alerting, maintenance/storage hassles, and spotty coverage
- As of late 2024, Indian zones—including Eastern Railway—continue to keep adequate stocks and deploy detonators systematically when visibility dips below specified thresholds
- Some zones (e.g., Ferozepur division) still lack automatic block signalling and thus are more dependent on traditional detonator signaling, even causing significant operational delays
Other Countries
- In the UK, detonators remain part of safety procedures in foggy conditions, with train crews carrying a set of them for emergency, assistance, or possession protection as needed
- In the U.S., torpedoes are basically obsolete due to soundproof cabs but still occasionally appear in use for track protection or flagging activities
- Other countries like Germany phased them out (e.g. 1986), and Taiwan replaced them with radio communication by the 1950s
🧭 Summary Table
| Region | Still Used? | Context / Reason |
|---|---|---|
| India | Yes | Fog safety in low-visibility zones; tech alternatives not fully reliable yet |
| UK | Yes | Part of formal fog-signal procedures |
| USA | Rare | Largely obsolete; rescued occasionally for emergency track protection |
| Germany, Taiwan | No | Replaced by modern signalling and communication systems |
🧠 Why Haven’t They Been Fully Replaced?
- Detonators work passively and locally, independent of radio, GPS accuracy, power, or connectivity.
- The explosion occurs directly under train wheels—an unmissable cue, even in very heavy fog or darkness.
- Alternatives like FogPass or Kavach systems exist but may fail with physical damage, irritate drivers, or require upkeep and storage when seasonal
- Regulatory procedure, low implementation cost, and well‑used protocols (e.g. placement routines, safety spacing) make them durable in practice.
✅ Bottom Line
Yes—detonators are still in active use, especially by Indian Railways in fog-prone zones, and also maintained in procedures by railways in the UK. While more advanced signalling and warning systems exist and are gradually replacing them in many places, detonators remain a reliable and low-tech fallback safety tool in many parts of the rail network today.
Would you like to know more about how they’re phased out in specific countries or details about modern fog-safety systems like FSD or Kavach?