Two-lane expressway

A two-lane expressway or two-lane freeway is an expressway or freeway with only one lane in each direction, and usually no median barrier. It may be built that way because of constraints, or may be intended for expansion once traffic volumes rise. The term super two is often used by roadgeeks for this type of road, but traffic engineers use that term for a high-quality surface road. Most of these roads are not tolled.
A somewhat related concept is a "four-lane undivided freeway". This is much rarer; a current example is U.S. Route 101 in California through Humboldt Redwoods State Park.
In Europe, the concept of express road encompasses roads which are classified between a motorway and an ordinary road. It does not necessarily have two lanes. This concept is recognized both by European Union law and under the UNECE treaty. This type of road is not very standardized, and its geometry may vary from country to country or within a same country. These roads are usually, but not always, limited-access roads. Some European Union regulation considers the high-quality roads to be roads "which play an important role in long-distance freight and passenger traffic, integrate the main urban and economic centres, interconnect with other transport modes and link mountainous, remote, landlocked and peripheral NUTS 2 regions to central regions of the Union". According to this same regulation "High-quality roads shall be specially designed and built for motor traffic, and shall be either motorways, express roads or conventional strategic roads." Eurostat and the United Nations Economic and Social Commission for Western Asia define an express road as a limited-access road that has signs reserving the roadway for specific categories of motor vehicles and that prohibits stopping and parking.
Two-lane freeways are usually built as a temporary solution due to lack of funds, as an environmental compromise or as a way to overcome problems constrained from highway reconstruction when there are four lanes or more. If the road is widened, the existing road is typically allocated to traffic going in one direction, and the lanes for the other direction are built as a whole new roadbed adjacent to the existing one. When upgraded in this manner, the road becomes a typical freeway. Many two-lane freeways are built so that when the road is upgraded to a proper divided freeway, the existing overpasses and ramps do not need reconstruction.
A super-2 expressway is a high-speed surface road with at-grade intersections, depending on the common usage of the term expressway in the area. By this definition, Super-2s can be considered the first stage of project which is expected to become a full freeway, with the transportation authority owning the land necessary for the future adjacent carriageway. At-grade intersections exist but there is sufficient land to replace them with interchanges. In some US states, a super-2 expressway is simply referred to as a super-2, regardless of whether it is fully controlled-access or not. Highway 410 in Ontario was originally a super-2 before being upgraded to a full freeway. Similarly, most of Highway 102 in Nova Scotia was a super-2 for three decades before being upgraded. Many super-2 expressways are simply just short transitional segments between surface street and four-lane divided freeways.
A super-4 expressway is a multi-lane divided highway with at-grade intersections, although the highway will become a full controlled-access freeway if the intersections are replaced with interchanges. A super-4 may have been a super-2 that has been twinned, although such instances of super-4 intermediaries are rare as super-2s are often upgraded right away to full freeways. Highway 40 in Ontario is a super-4 expressway between Highway 402 and Wellington St., and from Indian Rd to Rokeby Line. The remaining sections of Highway 40 are super-2 expressways. Other super-4 expressways include the Hanlon Parkway in Guelph and Black Creek Drive in Toronto, both which have sufficient right of way to allow for interchanges and overpasses to replace the at-grade crossings.
When a super-2 expressway is converted to a four-lane divided freeway, artifacts on the existing roadbed such as double yellow lines or broken yellow lines in passing zones are removed in favor of road markings for four-lane divided expressways.
While most expressways in Japan are four-lane divided expressways with median barriers, some expressways in rural areas are two-lane expressways, such as some sections of the Hokkaidō Expressway. The two-lane expressways in Japan are built in the same manner as the ordinary four-lane expressways with grade-separated interchanges and full access control, allowing future conversions to full four-lane divided expressways.
The two-lane expressway is not a new concept in Malaysia, as the Kuala Lumpur–Karak Expressway was initially a two-lane toll expressway before being upgraded to a full expressway in 1997. While the full four-lane divided toll expressways are more favored in recent years due to their higher traffic capacity, a few two-lane expressways do exist, such as the Kempas Highway and the North Klang Straits Bypass. These expressways, however, only have partial access control with at-grade intersections commonly available like most other federal and state roads. Nevertheless, these two-lane highways are still classified as "two-lane expressways" as they are maintained by highway concessionaires, namely PLUS Expressways Berhad (Kempas Highway) and Shapadu (North Klang Straits Bypass). Meanwhile, the South Klang Valley Expressway at Teluk Panglima Garang is a two-lane carriageway making it the first true two-lane expressway in Klang Valley and the second in Malaysia.
The first true two-lane expressway with full access control is the section of the Senai–Desaru Expressway between Cahaya Baru and Penawar.
Some sections of two-lane freeway can be found on the N1 and the N2 highways.
A portion of State Route 80 in the vicinity of Bisbee is a two-lane expressway with an interchange at West Boulevard and Tombstone Canyon Road (Historic US 80).
A 1.8 mile section of the State Road 912 freeway in East Chicago, Indiana is 2 lanes. This 2-lane section includes a new bridge over the Indiana Harbor and Ship Canal that opened in 2020. The original bridge that was closed in 2009 and demolished in 2012 carried 6 lanes of traffic.
The section from Yen Bai City to Lao Cai City of the Hanoi-Lao Cai Expressway is two-laned.
The section between Cam Lo and Hoa Lien of the North-South expressway is two-laned.