What is a normal reaction time for drivers?

Much slower than a reaction test shows. On a phone test most adults land somewhere around a quarter of a second. Road design in the US assumes 2.5 seconds from seeing a hazard to braking, and the UK Highway Code’s thinking distances work out to about two thirds of a second. The gap is the time it takes to notice, understand and decide.

Why the numbers differ

A simple reaction test gives you one signal you are waiting for. Driving adds steps:

1. Notice something in a busy scene.
2. Recognise it as a hazard.
3. Decide to brake rather than steer.
4. Move your foot from accelerator to brake.

Engineers call the whole chain perception-reaction time. AASHTO’s 2.5 seconds is meant to cover most drivers, not the average one.

What it does to stopping distance

During the reaction time the car keeps going at full speed. At 50 km/h a car covers about 14 metres per second, so 1.5 seconds of reaction is about 21 metres before the brakes even start working. At 100 km/h it doubles.

Speed	Metres per second	Distance in 1.5 s
30 km/h	8.3	12.5 m
50 km/h	13.9	21 m
100 km/h	27.8	42 m

Where a phone game fits

Cowboy Duel (my app) times how fast you flip your phone after the signal, in milliseconds, and catches false starts. It’s a game for simple reaction. It’s not a driving test, a fitness-to-drive check or a way to tell whether you are tired or impaired. If a test like this shows you much slower than usual, take that as a reason to rest, not as a licence to drive when you’re quick.

Related: what is a good reaction time and the Cowboy Duel guides.