Alternating three-lane road
An alternating three-lane street or a street in the 2 + 1 system is a street that is alternately divided into one or two lanes. They arose primarily from roads that - as in France - were previously three-lane, with the middle lane being the overtaking lane for both directions or, as in Sweden, from the expansion of former two-lane roads.
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Many three-lane roads were laid out in France in the 1960s. Since the central lane was designed as a passing lane for both directions of travel, many frontal collisions were the result. Therefore, starting in the 1990s, these were converted into alternating three-lane roads. In Switzerland, three-lane roads based on the French model would theoretically have been possible - there was still a question in the theoretical driving test in 1998 - but there were almost exclusively three-lane roads built there, such as Hauptstrasse 1 between Lausanne and Payerne, which has existed since the 1970s.
In Sweden, most of the 2 + 1-väg were created between 1990 and 2000 as a result of the expansion of what were once wide two-lane roads. A total of over 1,000 kilometers of alternating three-lane roads with central barriers were built. In New Zealand, such roads are known as passing lanes and can be found across the country. In Germany, such roads are referred to as the " 2 + 1 system ", since 2013 as trunk roads .
