Written by Muneeb Rana · Last updated 26 October 2026
Quick answer: GPS in tunnels stops working because rock, concrete and soil block satellite signals. A speedometer app will usually freeze its last speed or fall to zero until you exit, and distance for the tunnel may be under-counted. Some navigation apps estimate your position with motion sensors; a car's own speedometer is unaffected.
TL;DR
- Satellite signals cannot penetrate tunnels.
- Readings freeze or drop.
- Distance may be cut short.
- Recovers seconds after exit.
- Follow the dashboard and signs.
Why GPS in tunnels fails
GNSS signals are weak by the time they reach Earth and cannot pass through rock or thick concrete. Without at least four satellites the receiver cannot compute position or velocity.
What apps do
Some navigation apps use dead reckoning, estimating motion from accelerometers and the last known speed. Some tunnels install beacons. A phone speedometer typically shows the last value or zero.
Effect on distance
If the app joins the last point before the tunnel to the first after, curved tunnels lose some distance. Long tunnels can make trip averages look odd.
Similar trouble spots
| Place | Effect |
|---|---|
| Underpasses | Brief dropout |
| Multistorey car parks | No fix |
| Urban canyons | Spikes |
| Covered stations | Loss |
Safety
Tunnel speed limits are enforced in many places, sometimes by average-speed cameras. Use the car's speedometer, keep distance (the Highway Code advises a two-second gap in tunnels) and never fiddle with the phone.
What happens on exit
When you leave a tunnel the phone needs a few seconds to reacquire satellites. Speed may show zero or freeze, then jump. Distance covered inside may be missed or added as a straight line.
Tunnel safety
Tunnels have their own rules: keep distance, turn on headlights, and follow signs. In the UK and Europe, average speed cameras are sometimes used in long tunnels. Your car's speedometer is the instrument that works throughout.
What happens on the way out
When you leave a tunnel, the receiver needs a moment to reacquire satellites. Modern phones keep recent satellite data in memory, so this is usually quick, often a few seconds. During that gap the speed may show zero, freeze, or jump when the first new fix arrives. A trip distance can therefore come up a little short for routes with many tunnels, because the straight-line gap between the last fix before and the first fix after may be counted, or the missing stretch may be skipped. Long tunnels in mountain regions or under cities are the worst case. If exact distance matters, for example for expenses, use the vehicle's odometer for those trips.
Read next
GPS speedometer accuracy and speedometer app not working.
Related: GPS speedometer guide · GPS speedometer accuracy: how accurate is it? · Speedometer app not working? Try these fixes · How to improve GPS signal · Speedometer without GPS: what works? · Speedometer app safety: how to use it without distraction · Digital speedometer: big numbers at a glance · Analog speedometer: a classic needle dial
Get Speedometer PRO on Google Play · Download on the App Store · Set it up before you move; never handle your phone while driving.
Sources
- GPS Accuracy (GPS.gov): gps.gov (accessed 26 October 2026)
- Urban canyon (Wikipedia): en.wikipedia.org (accessed 26 October 2026)
- The Highway Code, rules 103-158 incl. stopping distances (GOV.UK): gov.uk (accessed 26 October 2026)
- Satellite navigation (Wikipedia): en.wikipedia.org (accessed 26 October 2026)
- Average speed camera (Wikipedia): en.wikipedia.org (accessed 26 October 2026)
FAQ
Why does my speedometer app freeze in tunnels?
Satellite signals cannot reach the phone underground, so it has no new speed data until you exit.
Does Google Maps work in tunnels?
Navigation apps may estimate your position with motion sensors, but accuracy drops until signal returns.
Will my trip distance be wrong?
It may be slightly short for curved tunnels, because the app connects points on each side.
How long until GPS recovers?
Usually a few seconds after leaving the tunnel, once satellites are visible again.
Which speed should I follow in a tunnel?
Your car's speedometer, which works without satellite signals.