"Four lane" refers to a road or highway that has two lanes going in each direction. However, there are several synonyms for this term. Some people refer to a "four lane" as a "dual carriageway", which is a British term that also means two lanes in each direction. Another synonym for "four lane" is "divided highway", which is a road that has a median or barrier separating the two directions of traffic. Others may call it a "multi-lane road" or a "four-lane highway". No matter what you call it, a "four lane" is a common type of roadway designed to handle high volumes of traffic.