Super-two

A super two, super two-lane highway or wide two lane, in the United States, is a two-lane surface road built to highway standards, typically including partial control of access, occasional passing lanes and hard shoulders. It is often built for eventual conversion to freeway or at least divided highway status once traffic volumes rise. It has also been used in cases where environmental concerns are prevalent, such as where Interstate 93 becomes a super two in Franconia Notch, New Hampshire.

In Ireland, the term wide two-lane is used by the National Roads Authority in the planning of routes using such a road type. In policy documents, the designation WS2 is used.

Wide two-lane roads are common on national roads, both on less important but medium-capacity routes, and on more important routes not yet upgraded to dual carriageway or motorway. Wide two-lane roads in the Republic generally have hard shoulders and are undivided single carriageway. Grade separation of junctions has been used on some schemes—for example the N20 bypassing Croom. Most wide two lane roads are wide enough that one can overtake without crossing the center line, if a vehicle in front pulls into the hard shoulder (the carriageway including hard shoulders is 15–17 metres wide).

Many future national road schemes in the Republic will use 2+1 roads or 2+2 roads, as opposed to wide two lane which is considered to better suit lower capacities than that catered for by 2+1. Wide two lane, if finished to particularly high quality, with grade separated interchanges, has been shown to lead to a false sense of security (from the apparently high speed road) and more dangerous driving (due to the carriageways not being separated).

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Wikipedia