Speed limits, safe following distance and stopping
This domain tests whether you can choose a safe speed, keep a safe gap and estimate stopping distance. Speed is not a single number: the posted limit is a maximum, while the safe speed depends on visibility, surface, load and the presence of people or animals.
Limits and signs
Mali sets a default urban limit of 50 km/h. Outside built-up areas the limit is higher and is always shown by signs, so read the sign rather than assuming a national figure. Lower limits apply near schools, in villages, at roadworks and where signing says so. Speed must also suit dust, rain, darkness and livestock.
Following and stopping
Use the two-second rule in dry conditions; double it to four seconds in rain, dust or darkness. Stopping distance has two parts: reaction distance (speed × reaction time) and braking distance, which rises with the square of speed. A loaded vehicle or a wet road lengthens both.
Worked example
At 50 km/h, 50 ÷ 3.6 ≈ 14 m/s. With a 1-second reaction, you travel about 14 m before braking; braking adds roughly 14 m, so total stopping distance is about 28 m. A two-second gap is about 28 m - the minimum, not a target.
Traps
Treating the limit as a target; tailgating to discourage overtaking; forgetting that a loaded vehicle or wet road lengthens braking; overtaking just where the limit drops.