Speed limits, safe following distance and stopping
What this domain tests
Whether you can choose a safe speed and calculate the distance needed to stop instead of quoting a rule of thumb wrongly.
Limits
Saudi Arabia sets default maximums of about 120 km/h on expressways, 100 km/h on rural highways and 40–80 km/h on urban roads. The posted sign always governs, and lower limits apply in school zones, roadworks, and during dust or rain. A limit is a maximum for perfect conditions, not a target.
Following distance
Use time, not metres or car lengths. Pick a fixed object; as the vehicle ahead passes it, count 'one thousand and one, one thousand and two'. If you reach the object sooner, you are too close. Double to four seconds on sand, wet roads or at night.
Stopping distance
Total stopping distance = thinking (reaction) distance + braking distance. At 100 km/h you cover about 28 m per second, so one second of reaction is 28 m and braking adds roughly 60–70 m: a real stop is 90–100 m, far more than most riders guess. Braking distance rises with the square of speed - 120 km/h needs about 45% more than 100 km/h.
Worked example
You are doing 100 km/h, two seconds behind a car - about 55 m back. It brakes hard. Your reaction consumes 28 m, leaving 27 m of gap, while you actually need 60 m or more to stop. That is why two seconds at highway speed is a bare minimum on a motorcycle with one small front contact patch.
Traps
Confusing 'two car lengths' with two seconds; forgetting that sand, heat-softened asphalt and worn tyres lengthen braking; and believing a lower speed limit protects you while you are still following too closely.