Lane discipline is the most visible part of professional driving. Every road user behind your vehicle has an opinion about which lane you are in, and the Highway Code’s rules 137 to 142 settle most of those opinions. For goods and passenger vehicle drivers there is an extra layer: weight and length change what “safe” means, and vehicle-specific lanes - crawler lanes, bus lanes, restricted lanes - apply to you directly.
Rule 137: on a two-lane dual carriageway you should stay in the left-hand lane; use the right-hand lane for overtaking or turning right; after overtaking, move back to the left-hand lane when it is safe to do so.
Rule 138 extends the same logic to three or more lanes: you may use the middle lanes or the right-hand lane to overtake, but you should return to the middle lanes and then the left-hand lane when it is safe to do so.
For heavy vehicles the overtaking decision is the whole game. Your overtake takes longer, your speed differential is smaller, and the elephant race - two limited trucks side by side for a mile over a 1 mph difference - is the single most complained-about behaviour in the sector. The rules do not forbid it, but the return-when-safe duty and basic professional courtesy both point the same way: only pull out when the speed gain is real, the completion is achievable, and the queue you create is short. And the return must be safe, which in a long vehicle means the overtaken vehicle fully visible in your mirrors, not just theoretically clear of your trailer’s swing.
Rule 139: climbing and crawler lanes are provided on some hills. Use this lane if you are driving a slow-moving vehicle or if there are vehicles behind you wishing to overtake. Be aware of the signs and road markings which indicate the lane is about to end.
This is one of the few places the Code effectively names the heavy vehicle: a loaded truck on a steep climb is exactly the slow-moving vehicle the lane exists for. Use it, even if you are climbing better than expected - the vehicles behind you cannot see your load weight, and the lane’s purpose is separating speeds. The end-of-lane warning matters twice over in a heavy vehicle: rejoining the main carriageway at crawler-lane end with closing faster traffic is a planned merge, not a surprise.
Rule 140 - cycle lanes: you MUST NOT drive or park in a cycle lane marked by a solid white line during its times of operation; do not drive or park in a broken-line cycle lane unless unavoidable; and you MUST NOT park in any cycle lane while waiting restrictions apply. The turning rule is the safety-critical one: give way to cyclists in a cycle lane, including when they are approaching from behind you - do not cut across them when turning or changing lane, and be prepared to stop and wait for a safe gap. For left-turning trucks in cities this is the blind-spot collision scenario the entire direct-vision debate is about: the cyclist alongside is your responsibility to see and to wait for. Note also that cyclists are not obliged to use cycle lanes - their absence from the lane does not mean absence from the road.
Rule 141 - bus lanes: shown by signs and markings indicating which vehicles may use them; unless otherwise indicated, do not drive in a bus lane during its period of operation. You may enter to stop, load or unload where this is not prohibited. The loading concession is the delivery driver’s friend, but it is local and signed - check the plate, because enforcement is camera-based and instant.
Rule 142 - high-occupancy and other designated vehicle lanes: you MUST NOT drive in such lanes during their times of operation unless signs indicate your vehicle is permitted. The permitted classes are entirely sign-dependent - buses, taxis, motorcycles, HOVs, sometimes HGVs, sometimes not - so the sign is the rule, read fresh at every lane.
Lane discipline complaints arrive as “your truck sat in lane two for six miles” photos. The counter is driver culture: brief the return-when-safe duty as a professional standard, discuss elephant-race restraint honestly, and treat crawler-lane use as a mark of competence rather than slowness. The driver who positions correctly, passes decisively and returns promptly is faster overall - and is the one the public never photographs.