2+1 road

2+1 road is a specific category of three-lane road, consisting of two lanes in one direction and one lane in the other, alternating every few kilometres, and separated usually with a steel cable barrier. Traditional roads of at least 13 metres (43 ft) width can be converted to 2+1 roads and reach near-motorway safety levels at a much lower cost than an actual conversion to motorway or dual carriageway. Denmark and Sweden have been building 2+1 roads since the 1990s.

By country

Ireland

In Ireland, a 2+1 road was trialled on a short section of the N20 near Mallow, County Cork. Following the pilot the National Roads Authority announced in July 2007 that 2+1 roads were unsuitable and that new lower capacity trunk routes would instead be built as 2+2 roads (officially known as Type 2 Dual Carriageways ) - at grade dual-carriageways with a narrow median and no hard shoulder.

Sweden

In Sweden, many 13-metre-wide (43 ft) roads have been built, especially in the period 1955–1980. These have two 3.5 metres (11 ft) wide lanes, and two 3 metres (9.8 ft) wide shoulders, in the beginning planned as emergency strip, due to the relative unreliability of autos of that period.