Road Rules for Heavy Vehicles
Road rules for heavy vehicles combine the general rules every driver obeys with extra obligations that arise from size, weight and stopping distance. You must understand priority rules at junctions and roundabouts, overtaking restrictions, speed limits (including lower limits for lorries and buses where posted), safe following distance, parking and stopping prohibitions, and rules for pedestrians and cyclists. In Sri Lanka, keep left is fundamental; on multi-lane roads you use the left lane unless overtaking, and you must not straddle lanes.
Traps in questions: assuming a heavy vehicle has right of way because of its size (it never does); confusing a 'no entry' with a 'no motor vehicles' sign; forgetting that a bus pulling out from a marked stop may have priority in some situations; and treating a broken white line as permission to overtake anywhere. Watch for questions about reversing (you must not reverse further than necessary and must have a competent person guiding where visibility is poor) and about loads overhanging, which change your road position.
Worked rule of thumb: at 50 km/h a loaded lorry may need 35–45 m to stop on dry tarmac, more when wet. Use the 'two-second rule' as a minimum in good conditions and double it in rain or when fully loaded. If the vehicle in front passes a fixed object, count 'one thousand and one, one thousand and two' - if you reach the object before finishing, you are too close.