A U-turn after the sign is

Explanation

In neither case.

The rectangular blue sign with the white upward arrow means "one-way road". Beyond it the entire traffic flow moves in one direction only, and movement in the opposite direction is prohibited. A U-turn is precisely a return in the opposite direction; so on such a road it is not made lawful by good visibility, by an empty road, or by "creating no obstruction".

The safety reason is clearer than any explanation: on a one-way road no driver expects an oncoming car. Drivers travel faster, with shorter gaps, and with no mental readiness for a head-on encounter; a car turning around raises the relative impact speed to the sum of both vehicles' speeds. To go back, change your route at the next intersection using roads where it is permitted.

Worth memorising, and the common trap: do not confuse this sign with the round blue "straight ahead only" sign. The round one prescribes the direction of travel at the intersection ahead; the rectangular blue one declares the status of the whole road and stays valid to that road's end. The shape — rectangle versus circle — is the fastest way to tell them apart. The "100 metres of visibility" option belongs to the conditions for U-turns on two-way roads and is simply irrelevant here.

• The "100 m visibility" condition concerns U-turns on ordinary roads; on a one-way road the issue is not visibility but movement in a forbidden direction. • "Creating no obstruction" is not what makes a U-turn lawful on a one-way road; even on a completely empty street, returning in the opposite direction is prohibited.

Sources and content coverage · Report a content error