2+1 road
Encyclopedia : 2 : 21 : 21R : 2+1 road
2+1 roads are country roads, usually with a steel cable barrier separating the oncoming traffic, having two lanes in one direction and one lane in the other, alternating every few kilometres. Traditional country roads of at least 13 metres 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. Denmark and Sweden have been building 2+1 roads since the 1990s.
Introduction of 2+1 in Ireland
In the Republic of Ireland, many national primary roads were upgraded in the 1990s and 2000s to wide two lane road (two lane road with space for three lanes, in addition to hard shoulders) to allow more space for overtaking (a very common manoeuvre in a country that had little dual carriageway until the early 2000s). However, due to the deceptive perception of safety given by such roads, many future upgrade projects are intended to be constructed as 2+1 road where traffic volume suits
A pilot installation was used on the N20 near Mallow, County Cork. As of 2006, the National Roads Authority has decided to install 2+1 on other routes; including some under construction in 2006. Full policy concerning 2+1 roads has not been finalised, as some pilot schemes are still in operation. It is likely that some current wide two lane roads, i.e. many of the new routes built in the 1990s and 2000s, will be retro-fitted with 2+1. Ordinary two lane, and even wide two lane, will still be used on routes requiring lower capacity. Dual carriageway/motorway is being installed on the major high capacity national primary roads.
As of 2006, existing 2+1 roads in the Republic of Ireland use a central crash barrier of similar design to that installed from 2004 onwards for straight sections of dual-carriageways and motorways (prior to 2004, only narrow median and obstacles such as flyover supports and embankments used crash barriers). These barriers consist of closely spaced poles, fixed below ground, carrying three high-tension thick wound cables. There are interim plans for maintaining these barriers daily, as they require prompt attention in the event of their being damaged in an accident.
| Examples of signage used in Ireland for 2+1 roads: | |||
|
Two lanes ahead |
Merge to single lane ahead |
Single lane only |
Two way traffic (opposing lanes) (Returning to undivided two lane road) |
See also
References
- [2+1 roads - Danish experiences], report from Danmarks Transportforskning, November 16, 2001
- [National Roads Authority]:
- *[Interim Advice Note on Road Link Design for 2+1 roads] (PDF 4.7MB)
- *[Scheme Activity 2006] (details of projects under construction or to begin in 2006)
- *[Major National Road Schemes in Planning]
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