CONVENTION ON ROAD TRAFFIC
The Contracting Parties, desiring to facilitate international road traffic and to increase road safety through the adoption of uniform traffic rules, have agreed upon the following provisions:
Chapter II
RULES OF THE ROAD
ARTICLE 12
Passing of oncoming traffic
1. When passing oncoming traffic, a driver shall leave sufficient lateral space and, if necessary, move close to the edge of the carriageway appropriate to the direction of traffic. If in so doing he finds his progress impeded by an obstruction or by the presence of other road-users, he shall slow down and if necessary stop to allow the oncoming road-user or road-users to pass.
2. On mountain roads and steep roads with characteristics similar to those of mountain roads, where the passing of oncoming traffic is impossible or difficult, it is the driver of the vehicle travelling downhill who should pull in to the side of the road in order to allow any vehicle proceeding uphill to pass, except where the arrangement of lay-bys to enable vehicles to pull in to the side of the road is such that, having regard to the speed and position of the vehicles, the vehicle proceeding uphill has a lay-by ahead of it and the need for one of the vehicles to reverse could be avoided if the vehicle proceeding uphill pulled in to that lay-by. Where one of the two vehicles which are about to pass is obliged to reverse in order to make passing possible, this manoeuvre shall be performed by the driver of the vehicle proceeding downhill unless it can manifestly be more easily performed by the driver of the vehicle proceeding uphill.
However, Contracting Parties or subdivisions thereof may prescribe for certain vehicles or certain roads or sections of roads special rules differing from those laid down in this paragraph.