Tri-Netra in Trains: What It Was, and What Indian Railways Actually Uses for Fog Safety
Last updated: 17 July 2026
In 2016 Indian Railways announced Tri-Netra, a “third eye” for loco pilots that would let them see through fog, heavy rain and darkness using technology borrowed from fighter aircraft and naval ships. The idea drew wide attention. This page explains what Tri-Netra was meant to do, what became of it, and which systems now actually protect trains in poor visibility.
Status: Tri-Netra never entered regular service. Railways floated the concept in 2016 and received strong interest from defence technology firms, with reports at the time suggesting around 3,000 trains would carry the system by the end of 2017. That target passed without deployment, and the technology has remained at trial stage. Meanwhile, Railways equipped loco pilots with Fog PASS devices, a simpler GPS-based solution now in wide use.
What Tri-Netra Was Meant to Be
TRI-NETRA stood for Terrain Imaging for Diesel Drivers Infra-red, Enhanced Optical and Radar Assisted System. As the name suggests, it combined three sensing technologies, which together would act as the three eyes of the loco pilot:
| Component | Purpose |
|---|---|
| High-resolution optical video camera | Normal visual imaging of the track ahead |
| High-sensitivity infra-red video camera | Seeing through darkness and poor light |
| Radar-based terrain mapping | Detecting obstructions and mapping the route ahead |
The system would merge these three feeds into a single composite image on a monitor in the cab. Designers expected it to pick up obstructions two to three kilometres ahead.
The Problem It Aimed to Solve
A loco pilot must be able to stop the train after spotting an obstruction, which means matching speed to visibility. On a clear day that poses no difficulty. In dense fog, heavy rain or darkness, however, the pilot has to slow down sharply, because a stalled vehicle at a level crossing or a fallen tree may appear far too late.
Northern India feels this every winter. During a bad fog season, dozens of trains face cancellation each day and many more run late. Tri-Netra promised to let trains keep moving at 25 to 40 kmph even in poor visibility, since the pilot could see a clear track ahead on screen rather than guessing.
Where the Idea Came From
Railway Board’s development cell drew on two military technologies: the vision systems that let fighter pilots operate through cloud and darkness, and the sonar-style mapping that helps naval ships navigate at night. No railway anywhere had adapted these for civilian rail use, which is precisely why the concept attracted attention.
After Railways published its expression of interest, around seven defence technology companies responded, from Israel, Finland, the United States, Austria and India. Reports at the time named firms including Elbit Systems, VTT Technical Research Centre and Tata Power SED among those interested.
What Happened Next
The project did not progress from concept to fleet deployment. Price bids and cost estimates proved harder to settle than expected, and the ambitious 2017 timeline slipped away. Trials continued in some form, yet no widespread rollout followed.
Consequently, Railways turned to a far simpler and cheaper answer for the fog problem, and that is what loco pilots use today.
Fog PASS: What Loco Pilots Actually Use
The Fog Pilot Assistance System for Safety, usually called Fog PASS, is a GPS-based navigation device that Railways has issued in large numbers. Around 19,742 devices have gone to zonal railways across the network.
Rather than trying to see through fog, it tells the pilot exactly what lies ahead based on GPS position and stored route data:
- It announces the next three fixed landmarks in order, giving both a screen display and a voice message roughly 500 metres before each one.
- Those landmarks include signals, level crossing gates both manned and unmanned, permanent speed restrictions and neutral sections.
- It works on single and double line, electrified and non-electrified sections alike.
- It suits every traction type, covering electric and diesel locomotives as well as EMU, MEMU and DEMU rakes, at speeds up to 160 kmph.
- It weighs under 1.5 kg, runs 18 hours on its battery, and works as a standalone unit that the pilot carries to the cab and places on the desk.
- Fog, rain and bright sunshine do not affect it, since it relies on satellite positioning rather than optics.
Why this worked better: Fog PASS sidesteps the hardest part of the Tri-Netra problem. Instead of building an expensive sensor suite to see through fog, it simply tells the pilot where the next signal and crossing are. That makes it cheap, portable and quick to deploy across thousands of locomotives.
Other Fog Season Measures
Railways combines Fog PASS with several older practices during winter:
- Fogmen place detonators on the track ahead of signals, which crack loudly under the wheels and alert the pilot.
- Signalling adjustments, including converting some automatic sections to semi-automatic working.
- Speed restrictions on affected routes.
- Cancellation or rescheduling of services on the worst fog days.
Check our fog train status page during winter, and live running status before you travel.
Kavach: The Bigger Safety Story Now
For preventing collisions, the system that matters today is Kavach, the indigenous automatic train protection system developed with RDSO. Kavach applies the brakes automatically if a pilot misses a signal or if two trains approach on the same line, and Railways is commissioning it corridor by corridor across the network.
For the full picture, see our guide on train safety technologies in Indian Railway.
Frequently Asked Questions
What does Tri-Netra stand for?
Terrain Imaging for Diesel Drivers Infra-red, Enhanced Optical and Radar Assisted System. It combined an optical camera, an infra-red camera and radar terrain mapping.
Is Tri-Netra used in Indian trains?
No. Railways announced it in 2016 and drew interest from defence firms, but it never reached fleet deployment. Loco pilots use Fog PASS devices instead.
What is Fog PASS?
A portable GPS-based device that tells the loco pilot about upcoming signals, level crossings and speed restrictions through display and voice alerts, roughly 500 metres in advance. Nearly 20,000 units have gone to zonal railways.
Why did Tri-Netra not get deployed?
The project stayed at concept and trial stage. Timelines slipped past the 2017 target, and Railways adopted the simpler and cheaper Fog PASS approach for fog safety.
How does Railways handle fog now?
Through Fog PASS devices, detonators placed by fogmen, signalling changes, speed restrictions, and cancelling or rescheduling trains on severe days.
What prevents train collisions?
Kavach, the automatic train protection system, which brakes automatically if a signal gets passed at danger or two trains approach on the same line.
Quick Summary
| Tri-Netra | Announced 2016, never deployed in service |
| What it combined | Optical camera, infra-red camera, radar terrain mapping |
| Aim | Let pilots see the track ahead in fog, rain and darkness |
| What replaced it | Fog PASS, a GPS-based pilot assistance device |
| Fog PASS units | Around 19,742 issued to zonal railways |
| Collision prevention | Kavach automatic train protection |
Tri-Netra remains an interesting example of an ambitious idea that did not survive contact with cost and complexity. The practical answer proved far humbler: a handheld GPS unit that simply tells the pilot what is coming. For more, see our guides on train safety technologies and how to find cancelled trains.
Curious about railway safety technology? Ask in the comments and we will cover it in a future guide.