Road surface marking
From Wikipedia, the free encyclopedia
Road surface marking is any kind of device or material that is used on a road surface to convey official information.
Road surface markings are used on paved roadways to provide guidance and information to drivers and pedestrians. Uniformity of the markings is an important factor in minimizing confusion and uncertainty about their meaning. Countries and areas categorize road surface markings in different ways.
Road surface markings are either mechanical, non-mechanical, or temporary. They can be used to delineate traffic lanes, instruct motorists and pedestrians or serve as noise generators when run across a road, or attempt to wake a sleeping driver when installed in the shoulders of a road.
There is continuous effort to improve the road marking system. and technological breakthroughs include adding reflectivity, increasing longevity and lowering installation costs.
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[edit] Mechanical markers
Mechanical devices can be either raised or recessed into the road surface and either reflective or non-reflective. While generally permanent, they may also be moveable.
Bott's dots (low rounded white dots), named after the California engineer who came up with the idea, are one type of a mechanical non-reflective raised marker. Generally they are used to mark the edges of traffic lanes, frequently in conjunction with raised reflective markers.
Bott's dots are also used across a travel lane to draw the drivers attention to the road. They are frequently used in this way before toll booths to get the drivers attention so they slow down or when a significant drop in speed has happened like going into a school zone. They are normally only used in warm climates since snow plows usually remove them along with the snow.
Similar to Bott's dots, "rumble strips" are commonly used for the same purpose. A rumble strip is a simple trough (typically 1 cm deep and 10 cm wide) that is ground out of the asphalt or concrete in a perpendicular line across a roadway or shoulder. Usually closely grouped together, 5 or 10 of these troughs create a loud vibration when driven over that will alert a driver to various upcoming hazards. This type of rumble strip could be used to warn a driver of an approaching stop sign in a rural area. Another form of the rumble strip is continuously placed on the shoulder of a highway to wake drivers that may fall asleep while driving. Crossing the rumble strips placed on the shoulder of the road can wake the weary driver before they drive into the ditch.
Reflective markers, known as cat's eye in some countries, are used as travel lane dividers. By being reflective, they are more visible at night and in inclement weather. White and Yellow indicate their usual message while Red is used to indicate that you are traveling the wrong direction in a lane.
These markers can also be used for other purposes such as marking the locations of fire hydrants (blue) or at gates to gated communities to indicate that emergency service vehicles have a code or device that allows them to open the gate. In some countries like the United Kingdom, raised markers are also used to mark crosswalks to assist the blind in crossing streets.
In colder climates, reflective markers can be installed below ground using an elongated narrow triangle, cut into the Road surface that allows the device to be installed below the road surface. Newer technology now allows these to be placed above ground with snowploughable rails that attempt to protect the reflective components from the snowplough blade.
[edit] Non-mechanical markers
[edit] Paint
Paint, sometimes with additives like reflective glass beads, is generally used to mark travel lanes. It is also used to mark spaces in parking lots or special purpose spaces for handicap parking (blue), loading zones, or time restricted parking areas. Colors for these applications vary by locality. Paint is a low cost marking and has been in use since approximately the early 1950's.
Paint is usually applied right after the road has been paved. The road is marked commonly by a truck called a "Striper." These trucks contain hundreds of gallons of paint stored in huge drums which sit on the bed. The markings are controlled manually or automatically by the controller who sits on the bed. Paint is run through a series of hoses under air pressure and applied to the roadway surface. After application, the paint dries fairly quickly.
Painted symbols, such as turn-lane arrows or HOV lane markers, are applied manually using templates.
[edit] Plastic
Plastics were introduced in the late 1960s and early 1970s. Commonly referred to as "tape" or "cold plastic," this product is heavy-grade material with reflective beads embedded in the plastic. It is commonly used to mark crosswalks, stop bars and traffic guidances such as turn lanes, HOV lanes, train crossings, pedestrian crossings, taxi lanes, bus lanes, and bike lanes. Generally speaking, there are three ways to apply tape:
- Overlay - This method refers to the actual application being laid over the surface of the pavement. Using industrial-grade rubber cement, once the tape is combined with the pavement, it should last three years. Major obstacles to estimated life are snow-plows, salt, and mis-application.
- Inlay - In this case, the tape physically becomes part of the asphalt. Using the heat generated in the paving process, road workers lay special tape on the asphalt in the hardening process and pavers on rollers compress the two together.
- Hot Tape - This is the oldest method and is widely disappearing. During the process, the road worker lays out pre-manufactured shapes in the design required. Once in place, a blow torch is used to melt the plastic on the surface of the road. Typically, this is a slower process and more prone to a dull, burnt color of the finished product.
[edit] Epoxy
Epoxy has been in use since the late 1970's and has gained popularity over the 1990's as the technology has become more affordable and reliable. This material competes directly with plastic with respect to usage and cost.
[edit] Temporary Markers
Pylons are sometimes used to separate HOV lanes from regular traffic lanes. They are also used in areas where lanes are used at different times for travel in both directions. These pylons have shafts that drop into holes in the road surface. A good example of this type of use is the Golden Gate Bridge in San Francisco.
[edit] Country specific information
[edit] United States
In the U.S., the type, placement, and graphic standards of traffic signs and road surfaces are legally regulated — the Federal Highway Administration's Manual on Uniform Traffic Control Devices is the standard, although each state produces their own manual based upon the Federal manual.
Generally white lane markings indicate a separation between lanes traveling in the same direction while yellow markings indicate opposing traffic on the other side of the line. In some areas, such as Colorado, black material is applied on the surface before a shorter white line is painted. This improves the contrast of the marking against "white" concrete.
In California, the white round ceramic button reflectors used to mark lanes on most freeways are known as Botts dots, after Eugene Botts, the Caltrans engineer who invented the epoxy that keeps them glued down. A large number of California cities also use Botts dots on some (or all) major arterials. The notable exception is the City of Los Angeles, which cannot afford to maintain any raised lane markers due to its fiscal problems, and uses only paint.
In California and Nevada, the reflectors are usually the lines, and no paint is used. Exceptions include: freeways built from white concrete where painted stripes are added to make the lanes more visible through sun glare, freeways built so wide that the risk of drifting is minimal (e.g., Interstate 5 in the Central Valley), and freeways in areas where it snows in the winter (since the snowplows would scrape off the Botts Dots).
In general, broken lines mean passing is allowed, single solid lines mean pass only to avoid a hazard, and double solid lines mean it is prohibited, as it often is in tunnels.
Crosswalks are indicated at a minimum by a pair of white lines. On major boulevards, crosswalks are further highlighted by zebra stripes, which are large white rectangles in the crosswalk perpendicular to traffic.
[edit] Western Europe
Some Western European countries reserve white for routine lane markings of any kind, and use yellow to indicate when lanes are being shifted temporarily to make room for construction projects.
In the U.K., zig-zag lines painted on the street mark a pedestrian crossing area.
[edit] New Zealand
Although New Zealand follows the convention of a solid yellow line to indicate no passing on roads with two-way traffic, it uses long dashed white lines to indicate when passing against opposing traffic is allowed on two-lane roads and shorter ones to separate lanes going in the same direction, with humorous results.
