How Does Bus Speed Test Work?

The first time you run a check, your browser asks permission to use your location. Tap Allow — nothing reads your position until you do. Your choice is remembered, so the next time you test, it starts straight away.

Once you've said yes, your phone tracks where you are using the same satellite signals your maps app relies on, refreshing about once a second. There's nothing to set up — Bus Speed Test simply starts watching your movement.

On most phones the speed comes straight from the GPS chip. It doesn't measure how far you moved between two fixes; it measures the tiny shift in the frequency of each satellite's signal caused by your motion (the Doppler effect) and solves for your velocity directly. That's why GPS speed is usually more precise than GPS position.

On the rare device that can't report speed on its own, the check estimates it from how far you've travelled between updates instead — and only when the position fix is good enough to trust.

GPS can wobble by a few km/h even while you're sitting still. To keep things calm, any reading below walking pace is shown as 0, and a jump that would need more acceleration than a bus can physically manage is thrown away as a glitch — so what you see reflects real movement, not jitter.

As you ride, the page keeps a running tally of the distance you cover along with your average and top speed. Distance only accumulates while you're actually moving, so waiting at a red light or a bus stop won't pad your numbers.

Because time spent stopped still counts toward the average, a steady 50 km/h cruise interrupted by a long red light will show a lower average than the cruise on its own. That's also why a city bus's average is so far below its cruising speed — see the table further down.

Switch between km/h, mph, m/s or knots whenever you like — the reading converts instantly and your choice is remembered for next time.

• Tunnels and underpasses. With no sky, there's no fix. Many phones keep showing the last known speed for a second or two, then the dial pauses until the signal returns.
• Tunnel exits. The first fix after a gap can lag reality. If the bus braked hard inside the tunnel, the reading may run high for a moment before it catches up.
• Tall buildings. Signals bounce off glass and concrete ("multipath"), so position drifts and speed gets noisier in dense city centres.
• Metal and tinted glass. Some coaches and most trains have heat-reflective windows that weaken the signal. Holding the phone close to a window helps.
• Standing still. Raw GPS drift reads as 1–3 km/h at a stop. Bus Speed Test clamps this to 0 so it doesn't creep into your distance or average.
• Very low speeds. GPS speed error is proportionally larger when you're barely moving, so a crawl through traffic is the least precise part of any trip.

In the European Union and the United Kingdom, buses and coaches with more than eight passenger seats (vehicle categories M2 and M3) must be fitted with a speed limiter set to 100 km/h (62 mph). The rule dates back to Directive 92/24/EEC and has applied to in-service vehicles in the UK since 2005. Since July 2024, new vehicles must also carry Intelligent Speed Assistance, which warns the driver or eases off the accelerator when the local limit is exceeded. Many operators set their own limiters lower still. A coach engine could push well past 100 km/h; the electronics simply won't let it.

The United States has no federal speed cap for buses. School buses are instead limited by state law, typically to 45 mph on ordinary roads and 55–60 mph on interstates, while intercity coaches follow the same limits as other commercial highway traffic.

If your bus shows 30 km/h on a city street, that's normal. If a coach shows a steady 98–100 km/h on the motorway, that's the limiter doing its job. A reading well above 100 km/h on a coach in Europe is more likely a momentary GPS glitch than a speeding driver — wait a few seconds and see if it holds.