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 usually separated with a steel cable barrier. The second lane allows faster-moving traffic to overtake slower vehicles at regular intervals. Traditional roads of at least 10 metres (33 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.

Sometimes, during freeway reconstruction, a barrier transfer machine will be used on one half of the freeway while the other is being reconstructed.

In 2023 the province of Ontario announced an assessment and design contract was awarded to convert Highway 11 north of North Bay to a 2+1 design; once the design has been finalized there will be a tender to build it.

The construction of 2+1 roads in Estonia first started in autumn 2016, when a contract for a reconstruction of a 9 kilometre section of the national road 4 between Ääsmäe and Kohatu into a 2+1 road was signed. The road is being reconstructed as a 15-metre-wide (49 ft) 2+1 road, equipped with barriers along the entire length.

Also there are several sections of the national road 2 between Põltsamaa and Tartu planned for a conversion into 2+1 road. The first of them (Annikvere-Neanurme) was opened in November 2017. The speed limits are 100 km/h (60 mph) during summer and 90 km/h (55 mph) during winter.

The first 2+1 road in Finland was opened in 1991 on Finnish national road 4 between Järvenpää and Mäntsälä, which later was upgraded to a motorway. Since then, numerous 2+1 roads have been built as part of the national road network. They resemble motorways in that they are typically, although not always, limited-access roads and have no at-grade interchanges. In the mid-1990s, 2+1 roads with traffic separators were introduced; these are effective in preventing head-on collisions, and approaching the safety of motorways. In 2006, there were 440 km of 2+1 roads, e.g., along road 3 and road 4. However, they weren't that much of a panacea: interchanges made the roads much more expensive than planned and confusing to drivers. Thus, new construction halted and only 2+2 roads with traffic separators were built. These are, however, more expensive and require more widening of the road.

The "2+1-System" refers to expressways with three lanes on a single carriageway where bypassing on the lane of the opposite direction is prohibited so that speed restriction is not required to increase safety. These expressways are grade-separated with a design speed of 100 to 120 km/h (60 to 75 mph) and the side of two lanes (allowing to bypass lower speed vehicles) alternates about every 1.5 to 2 kilometres. In hilly parts, the uphill direction is usually the one with two lanes to allow overtaking of heavy, slow vehicles. In many cases, there is no median barrier or it consists of concrete blocks – additional safety measures are mostly needed near the end of the two lane section where some motorists tend to pull in very late so that a longer no-traffic section needs to be inserted on the middle lane.

After some good experiences with test roads the system has been used often in places where the amount of traffic does not justify construction of a dual carriageway expressway but remote rural areas should be connected to major towns with a high speed road. Existing examples are B 1, B 4 near Uelzen, B 16, B 20, B 31n near Stockach (120 km/h (75 mph)), B 33, B 54, B 56n, B 67 between Bocholt-West and Borken, B 72, B 210, B 300, B 473 between Bocholt and Hamminkeln, B 482 and parts of the A 98.