Reaction time, attention time and total time
Reaction time, attention time and total time explain how quickly a driver can detect a hazard, decide on a response and start braking or steering. Knowing the numbers helps you choose safe margins and plan distance.
For the full driving process, see Traffic situations and the driving process . For braking calculations, see Reaction time and braking distance .
Attention time
Attention time is the time from a potential hazard first entering your awareness until you focus on it. Normal range with low distraction is 0.3–0.7 seconds.
| Factor | Typical attention time | Effect |
|---|---|---|
| Distractions | 0.5–1.0 s | Hazard spotted late |
| Experience | 0.3–0.6 s | Faster interpretation |
| Fatigue or stress | 0.6–1.2 s | Higher risk of misjudgment |
Reaction time
Reaction time runs from recognising the hazard to starting a physical action such as pressing the brake pedal. In good conditions it is usually 0.8–1.5 seconds.
| Component | Time (s) | Description |
|---|---|---|
| Identification | 0.1–0.5 | Understand what is happening |
| Decision | 0.1–0.5 | Select the correct response |
| Response | 0.1–0.5 | Move foot or hands to act |
Total time
Total time is the sum of attention time and reaction time. It covers the full delay from noticing a hazard to starting the action.
Total time = Attention time + Reaction time
Distance covered during total time
Distance travelled while you are still reacting is:
Distance = (Speed × total time) ÷ 3.6
| Speed | Total time (1.5 s) | Distance |
|---|---|---|
| 30 km/h | 1.5 s | 12.5 m |
| 50 km/h | 1.5 s | 20.8 m |
| 80 km/h | 1.5 s | 33.3 m |
| 100 km/h | 1.5 s | 41.7 m |
Factors that increase time
- Alcohol or drugs can double reaction time
- Mobile phone use increases attention time and delays decisions; see Distractions (mobile)
- Fatigue slows both perception and motor response; read Fitness to drive
- Health or age may limit eyesight, hearing or movement speed
Train faster decisions
Regular practice keeps routines sharp and lowers the total time in real traffic.
| Drill | How to do it | Effect |
|---|---|---|
| View scanning | Run 12–15 second scan patterns covering mirrors, instruments and road | Shorter attention time in complex scenes |
| Reaction training | Ask a supervisor to call out “stop” so you rehearse quick braking | Builds muscle memory for pedal changes |
| Scenario analysis | Review dashcam clips or tasks from the Traffic process guide | Improves recognition of decision points |
| Rest planning | Schedule a pause every 90 minutes and assess alertness | Prevents fatigue-related delays |
Everyday routines that help
- Build a fixed pre-drive check for seat, mirrors and visibility inspired by Technical safety check
- Enable do-not-disturb mode on the phone before departure and let passengers handle notifications
- Debrief the trip after parking: what went well and where could you react faster?
Driver assistance technology
Driver aids can warn earlier, but they never remove driver responsibility.
| System | What it does | What to watch out for |
|---|---|---|
| Adaptive cruise control | Keeps distance to the vehicle ahead, see Adaptive cruise control | May miss stationary objects; keep your foot ready |
| Lane keeping assist | Warns or steers when you drift, see Lane keeping assist | Needs hands on the wheel and clear lane markings |
| Automatic emergency braking | Brakes when a collision is imminent, see Automatic emergency braking | Can react late in rain or snow; maintain safe gaps |
For a complete overview of driver aids and responsibility, read Autopilot and driver assistance in practice .
Summary
- Attention time (0.3–0.7 s) + reaction time (0.8–1.5 s) ≈ total time (1.1–2.2 s)
- Use the formula to calculate how far you roll before braking starts
- Fatigue, alcohol and distraction make total time longer
- Training and wise use of driver aids reduce response distance but still require an alert driver