2+1 road
The second lane allows faster-moving traffic to overtake slower vehicles at regular intervals.
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.
However, they weren't that much of a panacea: interchanges made the roads much more expensive than planned and confusing to drivers.
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.
In New Zealand, there are few 2+1 roads, although regular isolated 'passing lanes' exist frequently throughout the country, mainly in heavily trafficked areas and on hills.
NZ research also investigated the design and operational effects of 2+1 roads to establish the most appropriate configurations for the country.
Almost every national road in the country has a 2+1 profile, but the biggest part is located in the north because of the hills (for example, in Beira Baixa, or Viseu).
The 2+1 road format in Romania often refers to sections, usually on steep inclines, where there is another lane, designed to be used by slow vehicles to avoid congestion when going uphill.
The first 2+1 "alternative" road opened between Lazaret and Turnul Spart in 2018 on the Olt Valley section of the DN7.
The DN2 is currently configured as a 13 m wide road with emergency lanes, in the same style as 13 m wide roads in Sweden, however, drivers improperly use the emergency lanes, leading to the current high number of crashes.
Once the roadworks will be completed, the 2+1 road is supposed to reduce the number of crashes, but it will lack the essential cable barrier.
The most prominent example is Interstate 93 in Franconia Notch State Park (before dropping down to a single lane in each direction, plus a steel divider).
Divided 2+1 roads are rare outside of Europe and the United States, though they are seen in a few places, such as Australia and the Canadian provinces of Ontario and Quebec.
