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