How fast is this train going?
Some trains have a screen that tells you. Most don't, and the ones that do often round it or show it for five seconds an hour. Press Start and this tells you continuously, on a dial that goes to 300 rather than stopping where a car's does.
The number worth watching is Max. A high-speed service spends most of its time below line speed and only touches it on the fastest sections, so leave it running and check the peak at the end.
Why do trains give such good readings?
Trains suit satellite positioning better than almost anything else on land. The track is straight or gently curved, speed is steady for long stretches, and railways run through open country far more often than roads do. Under those conditions a phone tracks speed to within a couple of km/h even at 300.
- Sit by a window. The middle of a carriage cuts your view of the sky a lot.
- Coated glass is the real problem. Many modern coaches, and most high-speed stock, have metallised windows that block satellites almost as well as the bodyshell. If accuracy stays bad by a window, that's usually why.
- Tunnels end it. The dot turns red within a few seconds and speed drops to zero. Your trip survives and picks up on the far side.
- Deep cuttings and station canopies hurt too, though less completely.
What the numbers mean on a train
- Average divides distance by total time, so every station stop drags it down. On a stopping service it can be less than half the line speed, which is exactly why an express saves so much time.
- Distance is measured along the track as you go, so it describes the route rather than the straight line between cities. It reads slightly short through tunnels, where the line drawn across the gap is shorter than the rails.
Line speeds worth knowing
| Service | Top speed | Where |
|---|---|---|
| Shinkansen N700S | 285 to 300 km/h | Japan |
| TGV | 300 to 320 km/h | France |
| ICE 3 | 300 km/h | Germany |
| Eurostar | 300 km/h | HS1 and LGV Nord |
| Frecciarossa 1000 | 300 km/h | Italy |
| CR400 Fuxing | 350 km/h | China |
| UK intercity | 200 km/h | ECML and WCML |
| Regional and commuter | 120 to 160 km/h | Most of Europe |
| Metro | 70 to 100 km/h | Underground, so no reading |
The record you won't see from a seat
The fastest a conventional train has gone on rails is 574.8 km/h, set by a modified TGV in 2007 on a test run. A Japanese maglev hit 603 km/h in 2015, though it wasn't touching the track. Scheduled services run well below those because wear, energy cost and safety margins all climb steeply with speed.
Battery and manners
GPS with the screen on is demanding, so use the socket at your seat if there is one. Turn the graph off to save a bit more. And if you have a neighbour, the dark theme is kinder on a night service.
Frequently asked questions
Why does the speed drop to zero in a tunnel?
No satellites underground. The dot turns red and the reading falls to zero within a few seconds. Your distance and top speed are kept, and measuring resumes when you come out.
It reads zero even by a window. Why?
Most high-speed and many modern regional coaches have metallised glazing, which blocks satellites nearly as well as the bodyshell. Try a door or vestibule window, which is often uncoated.
How accurate is it at 300 km/h?
Very. A train is close to the ideal case for GPS, so expect within a couple of km/h wherever the signal is good.
Why is my average so much lower than the speed I saw?
Average includes every station stop and slow section. On a stopping service it's often less than half the top speed. Compare Moving with Elapsed to see how much of the journey was spent standing.
Can I use it on the underground?
No. An underground line has no reception at all. It works on the surface sections of a metro, which many have.