Central reservation

From Wikipedia, the free encyclopedia.

(Redirected from Neutral ground)
Jump to: navigation, search
For "central reservations" (such as for hotels), see call center.

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

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 hedges of shrubs filter the headlights of oncoming traffic and provide a resilient barrier.

The central reservation in the United Kingdom 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 metres 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(M) 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).

A California arterial road median with rocks set in it
Enlarge
A California arterial road median with rocks set in it

In North America, 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. On arterial roads, traffic may be separated by landscaped medians, or by islands of concrete marked off with curbs; some U.S. states, such as California, have made such concrete islands more attractive by setting rocks in them.

One of the most famous medians is the famous "inverted" median of the Golden State Freeway (I-5) in the rugged Tehachapi Mountains between Los Angeles, California and the San Joaquin Valley. For several miles of the freeway, the median is inverted for several miles — that is, northbound traffic is in the western roadway, and southbound traffic is in the eastern road.

Trivia

Personal tools
In other languages