A one-way system sign is a traffic sign indicating that vehicles are only allowed to move in one direction on a particular road or street. These signs help regulate traffic flow, reduce congestion, and improve safety by preventing vehicles from going against the designated direction. The most recognizable one-way sign is typically a rectangular or circular sign with an arrow pointing in the permitted direction. In many countries, a blue circular sign with a white arrow shows the direction vehicles must travel. Additional signs often used in conjunction are "Do Not Enter" or "No Entry" signs, usually red with a white horizontal bar, placed at intersections or road ends where entry into the one-way street is prohibited to prevent wrong-way driving. The signs are usually placed at the entrances of the one-way street and along its length to remind drivers of the traffic flow direction. In some countries, the sign contains words such as "One Way" or the equivalent in the local language (e.g., EINBAHN in Austria or Sens unique in Luxembourg) inside or near the directional arrow. When drivers enter a one-way system, they must follow the arrow direction and choose the appropriate lane for their destination. One-way systems allow passing on either side, unlike two-way streets where vehicles keep to the left or right. Road markings and signage guide drivers on which lane to take, particularly for turns or continuing straight ahead. Overall, a one-way system sign plays a pivotal role in traffic management by ensuring vehicles move in a single direction, enhancing traffic flow efficiency and safety, especially in urban and congested areas.
