High Capacity Restricted Access Roads

Most high capacity roads are built to a higher standard than general purpose roads. In order to provide for higher traffic volumes, such routes may be operated with limited access points, and to particular types of motorized vehicles. Usually these high capacity routes are dual carriageway. Concepts that adhere to these qualities include; freeways, motorways, autobahns and autostrada.

United Kingdom

The M25, a typical motorway in the United Kingdom

In the UK the term motorway is used almost unanimously to refer to a specific type of road in the UK and the Republic of Ireland. Although the terms expressway, or parkway are sometimes used, they amount to little more than street names, with motorway the only term officially recognized. The UK motorways are engineered so that they are among the safest such roads in the world, with almost all motorways having a full-width hard shoulder (breakdown lane), full grade-separated interchanges with long on/off ramps and a barriered central reservation which is a compulsory requirement for a motorway (the term “median strip” is unknown in British English). Without a barried central reservation, or if a multilane road fails to meet any of the other requirements to become a motorway, it is simply referred to as a dual carriageway.

All UK motorways have an “M” prefix (e.g. M1) or, where an “A” road has been upgraded to motorway status, an “M” suffix in brackets (e.g. A1(M)).

United States Freeways

Interstate 80 (Eastshore Freeway) in Berkeley, a typical American freeway

In the United States of America, a freeway is a divided highway with full control of access. This means two things. First, adjoining property owners do not have a legal right of access, meaning that they cannot connect their lands to the highway by constructing driveways. When an existing road is converted into a freeway, all existing driveways must be removed and access to adjacent private lands must be blocked with fences or walls. Second, traffic on the highway is “free-flowing”, although many non-engineers misapprehend the “free” in “freeway” to mean that such a highway must be free of charge to use. All cross-traffic (and left-turning traffic) has been relegated to overpasses or underpasses, so that there are no traffic conflicts on the main line of the highway which must be regulated by a traffic light, stop signs, or other traffic control devices. Achieving such free flow requires the construction of many bridges, tunnels, and ramp systems. The advantage of grade-separated interchanges is that freeway drivers can almost always maintain their speed at junctions since they do not need to yield to crossing traffic.

Expressways

In contrast, an expressway is defined as a divided highway with partial control of access. Expressways may have driveways connecting to adjacent properties, although the trend over time has been to minimize driveways when possible. Expressways also may have at-grade intersections, though these tend to be spaced farther apart than on most arterial roads. In urban areas, expressway intersections are usually controlled by traffic lights, but in many rural areas, cross-traffic is governed only by stop signs, and there are no restrictions on through traffic. Vehicles crossing an expressway at rural intersections must cross four lanes with vehicles coming at them at prevailing speeds. Thus, expressways are more dangerous than freeways and cannot carry traffic as efficiently as a freeway.

Unit 9 Highway

Highway in Pennsylvania, USA Highway SP-160 in Brasil

Highway is a term commonly used in the United States to designate major roads intended for travel by the public between important destinations, such as cities.

Highway designs vary widely. They can include some characteristics of freeways and motorways such as multiple lanes of traffic, a median between lanes of opposing traffic, and access control (ramps and grade separation). Highways can also be as simple as a two-lane, shoulderless road. The United States has the largest network of national highways, including Interstate highways and United States Numbered Highways. This network is present in every state and connects all major cities. China has the fastest expanding and second largest highway system in the world.

Some highways, like the Pan-American Highway or the European routes, connect multiple countries. Australia’s Highway 1 connects all state capitals and runs almost the entire way around the country.

The longest single national highway in the world is the Trans-Canada Highway, which runs from Victoria, British Columbia, on the Pacific Coast, through ten provinces to the Atlantic Coast, at St. John’s, Newfoundland.

Highways are not always continuous stretches of pavement. For example, some highways are interrupted by bodies of water, and ferry routes may serve as sections of the highway.

Nomenclature

The terms used for various types of highways (such as autobahn, autoroute, expressway, freeway, and motorway) vary between countries or even regions within a country. In some places a highway is a specific type of major road that is distinct from freeway or expressway; in other places the terms may overlap. In law, highway may mean any public road or canal. However, in some countries, the term highway is not generally used at all.