u/AdPsychological3827

it says

"When crossing or turning right, first assess whether the central reservation is deep enough to protect the full length of your vehicle.

If it is, then you should treat each half of the carriageway as a separate road. Wait in the central reservation until there is a safe gap in the traffic on the second half of the road.

If the central reservation is too shallow for the length of your vehicle, wait until you can cross both carriageways in one go."

and the picture catptioned "Rule 173: Assess your vehicle’s length and do not obstruct traffic"

I'm not sure why it's talking about depth of central carriageway as it not like you're gonna drive over it

how can it be deep enough to protect your full length of the vehicle