Road culture runs on informal signals: the flash that means “after you”, the horn that means “look up”, the wave that means thanks. Professional drivers use them as much as anyone else - which is exactly why the Highway Code’s actual rules on horns and headlight flashing deserve a refresher. The informal versions are not just rude when misused; some of them are offences, and for a professional driver the gap between habit and law shows up in complaints, camera footage and collision reports.
Rule 110: only flash your headlights to let other road users know that you are there. Do not flash your headlights to convey any other message or intimidate other road users.
That single sentence outlaws most of what headlight flashing means in practice. The flash to concede priority at a narrow gap, the flash to say “I’m letting you out”, the flash to warn of a speed camera, the flash of frustration at a dawdler - none of them is the permitted meaning. The flash exists to announce presence: a vehicle approaching a hidden dip, a blind bend, a situation where being seen is the safety need.
Rule 111 is the mirror for everyone else: never assume that flashing headlights is a signal inviting you to proceed. Use your own judgement and proceed carefully. For drivers of large vehicles this cuts hard. A car flashes you out of a side road; your trailer swings across its path as you take the “invitation”; the other driver’s flash was never an invitation in law, and the collision analysis will not treat it as one. The rule assigns the decision to you, always - no flash transfers priority.
Rule 112: use the horn only while your vehicle is moving and you need to warn other road users of your presence. Never sound it aggressively. And the MUST NOTs: do not use your horn while stationary on the road, or when driving in a built-up area between 11.30pm and 7.00am - except when another road user poses a danger.
Every clause lands on real habits:
The exception that runs through all of it - another road user poses a danger - is the horn’s true purpose: the pedestrian stepping off the kerb into your path, the car drifting across the lane. Used for danger, the horn is exactly what the law wants. Used for commentary, it is prohibited, aggressive, or both.
The general signalling rules complete the picture. Signals warn and inform other road users of your intended actions: give clear signals in plenty of time, having checked it is not misleading to signal at that time; cancel them after use; do not signal in a way that confuses - the Code’s example is signalling before a side road you are passing, which reads as an intention to turn into it; and use an arm signal to emphasise or reinforce if necessary. Then the sentence professionals should have on the cab wall: signalling does not give you priority. The indicator is information, never a claim. A 44-tonne vehicle signalling a lane change is announcing a need, not acquiring a right - the space must still be yielded by someone else, on Rule 111’s logic and theirs.
Complaints about professional drivers disproportionately feature exactly these behaviours: the aggressive horn, the intimidating flash, the horn in a sleeping street. Each is a small rule with a public face, and each is camera-captured by the public’s dashcams with your livery attached. Brief the rules as rules, correct the habits as habits, and the fleet’s road manners become one less thing to defend.