Clause 9.8 (9 "Warning signals", subclause "a")

While driving mechanical vehicles during daylight hours, in order to indicate a moving vehicle, the low beam headlights must be turned on: a) in a convoy.

This subclause directly specifies which warning signal is used during the day for vehicles moving in a convoy: it is the low beam headlights.

Clause 25.1 (25 "Movement of vehicles in convoys")

Each vehicle moving in a convoy must display the identification sign "Convoy", as provided for in subclause "ye" of clause 30.3 of these Rules, and the low beam headlights must be turned on. The identification sign may not be installed if the convoy is accompanied by emergency vehicles with flashing red, blue and red, green or blue and green beacons and/or special sound signals.

This clause establishes the obligation for each vehicle in the convoy to turn on the low beam headlights while moving (regardless of the time of day), and thus confirms the correct answer specifically for daylight hours.

Therefore, the correct answer is "Low beam headlights," given that according to the Traffic Rules, when vehicles are moving in a convoy (during daylight hours — as a warning signal), each of them must have the low beam headlights turned on (clauses 9.8 "a" and 25.1).

When vehicles move as an organized convoy, it is important for other road users to understand in advance that they are not seeing individual cars, but a group moving in coordination. That is why the Rules require a clear “visual sign” of the convoy while driving, even during the daytime.

Section 25 of the Traffic Rules (paragraph 25.1) states directly: each vehicle moving as part of a convoy must have its low beam headlights switched on while driving. This is done for better visibility and safety, so that drivers from other directions or neighboring lanes can see the convoy earlier and correctly assess its length.

In practice, this looks as follows: if, for example, ten cars are moving in a convoy during the day, all ten must drive with their low beam headlights on. Daylight does not cancel this requirement specifically for convoys: the purpose here is not to illuminate the road, but to clearly mark the vehicles moving together.

It is important not to confuse this with daytime running lights: they are used under separate conditions, while for convoys the Rules specify low beam headlights as the mandatory warning signal when driving during daylight hours.

Therefore, the correct answer is "Low beam headlights," because when moving as part of a convoy, each vehicle during daylight hours must be additionally marked by switching on its low beam headlights.