At 80 km/h on an open dry tarred road, what following gap does Rule 181's one-metre-per-km/h rule of thumb give, and how does it compare with the Rule 141 table overall stop?

1. 80 metres — a little more than the table's 54-metre shortest overall stop, so it includes a small extra margin
2. 8 metres — less than thinking distance alone
3. 16 metres — thinking distance only, ignoring braking
4. 38 metres — braking distance only, ignoring thinking