The Full Wiki

More info on Central reservation

Central reservation: Map

  
  

Wikipedia article:

Map showing all locations mentioned on Wikipedia article:



On divided roads, including expressways, motorways, or autobahns, the central reservation , median , median strip (North American English and Australian English) or central nature strip (Australian English) is the area which separates opposing lanes of traffic.

Physical attributes

Some medians function secondarily as "green areas", beautifying roadways. Some jurisdictions mow their medians, others scatter wildflower seeds which germinate and re-seed themselves every year, while still others create extensive plantings of trees, shrubs, herbaceous perennials and decorative grasses. Where space is at a premium, dense hedge of shrubs filter the headlights of oncoming traffic and provide a resilient barrier.

A California arterial road median with rocks set in it.
In contrast to major highway medians, urban road medians often take the form of central traffic islands that rise above the roadway. These are frequently found on urban arterial roads. In their simplest form, these are just raised concrete curbs, but can also be landscaped with grass or trees or decorated with bricks or stones. Such medians are also sometimes found on more minor or residential streets, where they serve primarily as a traffic-calming or landscaping element rather than a safety enhancement to restrict turns and separate opposite directions of high-volume traffic flow.

In some areas, such as Californiamarker, highway medians are sometimes no more than a reserved central section of the paved roadway, indicated by a space between two sets of double-yellow lines. Similar to an island median, vehicles are only permitted to cross at designated locations. This arrangement has been used to reduce costs, including narrower medians than are feasible with a planted strip, but research indicates that such narrow medians may have minimal safety benefit compared to no median at all.

On British motorways the central reservation is never broken (except on the tidal flow of Aston Expressway), but there are no such restrictions on other dual carriageways. The medians of United States Interstate Highways break only for emergency service lanes, again with no such restrictions on lower classification roads.

Width

The central reservation in the United Kingdommarker, and other densely populated European countries, is usually no wider than a single lane of traffic. In some cases, however, it is extended; for instance, if the road is running through hilly terrain, the carriageways may have to be built on different levels of the slope. Two examples of this on the UK road network are on a section of the M6 between Shap and Tebay, where the carriageways are several hundred yards apart allowing a local road to run between them, and on the M62 where the highest section through the Pennines famously splits wide enough for a farm in the central reservation. The other major exception is the A38 Aston Expressway, which is a single carriageway of seven lanes, where the median lane "moves" to account for traffic flow (a system known as tidal flow).

With effect from January 2005 and based primarily on safety grounds, the UK’s Highways Agency's policy is that all new motorway schemes are to use high containment concrete step barriers in the central reserve. All existing motorways will introduce concrete barriers into the central reserve as part of ongoing upgrades and through replacement as and when the current systems have reached the end of their useful life. This change of policy applies only to barriers in the central reserve of high speed roads and not to verge side barriers. Other routes will continue to use steel barriers.

In North America, and some other countries with large sparsely populated areas, opposing lanes of traffic may be separated by several hundred meters of fields or forests outside of heavily populated areas, but converge to a lane's width in suburban areas and cities. In urban areas, concrete barriers (such as Jersey barriers) and guard rails (or guide rails) are used.

One median of note is the "inverted" median of the Golden State Freeway (I-5) in the Tehachapi Mountains between Los Angeles, Californiamarker and the San Joaquin Valleymarker. For several miles the median is inverted — Northbound traffic is on the western roadway and southbound traffic on the eastern road. A similar example exists in western Montrealmarker, on the Autoroute 20marker, between the Route 138 and the Turcot Interchangemarker, where the two directions, on opposite sides of a railway, are reversed (and one enters or exits via the left side). Similarly, I-85, in central North Carolina, features an "inverted" median so that an in-median, right-exit rest area can feature a historic bridge.

Safety

An August 1993 study by the U.S. Federal Highway Administration quantified the correlation between median width and the reduction of both head-on accidents and severe injuries. The study found that medians without barriers should be constructed more than in order to have any effect on safety, and that safety benefits of medians increase to a width of to . A consequence of this finding is that decreasing the size of a median to from to add lanes to a highway may result in a less safe highway. Statistics regarding medians with barriers were not calculated in this study.

Trivia

  • The median for Canal Street in New Orleans (and by extension, for all streets in Greater New Orleans) is called "neutral ground" by local residents. (See: Regional vocabularies of American English.) This term stems from the city's early years. The American newcomers and the Creole old timers didn't get along with each other, and divided generally with Americans upriver from Canal Street and the Creoles downriver (in today's French Quartermarker). The wide area in the middle of Canal Street (where the canal was never dug) became known as the neutral ground, where members of the groups could transact business or otherwise mingle.


See also



References

  1. Google Maps



Embed code:






Got something to say? Make a comment.
Your name
Your email address
Message