Independent learning reference with original examples. Not official test questions or an individual licensing decision. Current official rules and your licence conditions apply.
Practise driving-skills questions →Use one marker and two bumper events
Choose a stationary roadside object. Start counting when the rear of the vehicle ahead passes it, then stop when your front bumper reaches it. If the interval is shorter than three seconds, drop back and check again. Counting while both cars are beside different objects does not measure the gap.
Use a steady seconds count rather than racing through the numbers. The purpose is room to observe and respond, not completing a chant before a sign disappears.
Source: SGI handbook — Time, the key to judgment ↗Seconds adapt to speed; a fixed number of car lengths does not
A car covers more ground in three seconds at highway speed than at city speed. That is why the same time gap represents a larger physical distance as speed rises. SGI illustrates this relationship in its time-distance table.
Do not treat the table as a promise that a particular gap prevents every collision. SGI explains that traction, the lead vehicle hitting a fixed object and slower driver response can require more than three seconds.
| Observation | What to do with it |
|---|---|
| Only two seconds at the marker | Increase the gap and measure again. |
| Three seconds in ideal conditions | This meets the handbook’s baseline recommendation. |
| Rain, ice or other reduced conditions | Allow more space rather than relying on the ideal-condition baseline. |
Find the measurement error or missing margin
Original worked examples
Fast counting: a learner reaches the sign after saying three numbers in two actual seconds. The spoken number is not evidence of a three-second interval. Recheck with a steady count.
Speed change: the learner keeps the same visual gap after accelerating onto a highway. The car now covers that gap sooner. Measure again using time instead of assuming the old space is enough.
Icy approach: a driver records exactly three seconds and declares the gap sufficient. That omits SGI’s condition qualifier. More time is needed when the surface reduces the available grip.
Following time is not the whole stopping distance
The gap is time between vehicles. Your own response and braking still take time and distance. If the leading car stops abruptly against an object, copying its earlier speed does not ensure you can stop where it did.
Read well ahead so that you can respond to developing hazards rather than waiting only for brake lamps. SGI’s explanation connects observation, decision-making, reaction and braking; it does not describe three seconds as a universal collision guarantee.
Source: SGI handbook — Time, the key to judgment ↗Explain a missed answer in terms of conditions
After a practice question, state whether it asked about the measurement method, the ideal-condition minimum or an increased margin. Those are separate decisions. An answer can correctly mention three seconds while still being unsuitable for an icy-road scenario.
The free driving-skills and winter topics provide further original questions. Learn the method from the current SGI handbook and use your supervisor’s guidance for real practice. This page is a study explanation, not a stopping-distance calculator.