Road surface marking
||The examples and perspective in this article deal primarily with the English-speaking world and do not represent a worldwide view of the subject. (April 2011)|
Road surface marking is any kind of device or material that is used on a road surface in order to convey official information. They can also be applied in other facilities used by vehicles to mark parking spaces or designate areas for other uses.
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, and efforts exist to standardize such markings across borders. However, countries and areas categorize and specify road surface markings in different ways.
Road surface markings are either mechanical, non-mechanical, or temporary. They can be used to delineate traffic lanes, inform 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. Road surface marking can also indicate regulation for parking and stopping.
There is continuous effort to improve the road marking system, and technological breakthroughs include adding retroreflectivity, increasing longevity, and lowering installation cost.
In the United States, the first documented use of a painted center line was in 1911 along Trenton's River Road in Wayne County, Michigan. According to the state of Michigan, the idea of using a painted center line was conceived in 1911 by Edward N. Hines, the chairman of the Wayne County, Michigan, Board of Roads, after watching a leaky milk wagon leave a white trail along a road. Hines was inducted posthumously in 1972 into the Michigan Transportation Hall of Honor for his innovation, and was honored in 2011 with the first Paul Mijksenaar Design for Function Award.
In 1917, the idea of using painted center lines on rural state highways was conceived and/or put into action in at least three states (Michigan, Oregon, and California), apparently completely independent of one another. At some point in 1917, a white highway center line was painted along "Dead Man's Curve" on what is now County Road 492 in Marquette County, Michigan, under the direction of Kenneth Ingalls Sawyer, who served as engineer-superintendent of the Marquette County Road Commission. Sawyer was inducted posthumously into the Michigan Transportation Hall of Honor in 1973.
In Oregon in April 1917, a yellow center line was painted down the center of the Columbia River Highway, between Crown Point and Multnomah Falls, at the direction of Multnomah County Sheriff's Deputy Peter Rexford. Later in 1917, the same line was continued west of Crown Point. Rexford first conceived the idea of a yellow center line in early 1917 while riding on a bus from Salem, Oregon on a dark and rainy night, and advocated it as a safety measure on the Columbia River Highway, which Rexford patrolled as a traffic officer. When Multnomah County declined to fund the project, Rexford's boss, Chief Deputy Martin T. Pratt (later elected Sheriff), paid for the paint out of his own pocket so that the center line could be painted. Rexford later described the April 1917 line as the "first yellow center line ever painted on pavement" in the United States. An article published in The Oregonian upon Rexford's retirement claimed that a contest with a $10,000 reward was once held to determine the originator of the highway center line, but the contest was scrapped when information from Europe revealed that ancient civilizations had used white bricks to mark the center lines of their streets.
In the fall of 1917, Dr. June McCarroll of Indio, California developed the idea of white center lines and began advocating for their use, after she was run off the road by a truck while driving along a highway that would later be incorporated into U.S. Route 99. Dr. McCarroll soon communicated her idea to the local chamber of commerce and the Riverside County Board of Supervisors, with no success. She then took it upon herself to hand-paint a white stripe down the middle of the road, thus establishing the actual width of the lane to prevent similar accidents. In 2002, a portion of Interstate 10 was designated and signed as "The Doctor June McCarroll Memorial Freeway" in her honor.
The question of which color to use for highway center lines in the United States enjoyed considerable debate and changing standards over a period of several decades. By November 1954, 47 states had adopted white as their standard color for highway centerlines, with Oregon being the last holdout to use yellow. In 1958, the U.S. Bureau of Public Roads adopted white as the standard color for the new interstate highway system. The 1971 edition of the Manual on Uniform Traffic Control Devices, however, mandated yellow as the standard color of center lines nationwide. The changeover to the 1971 MUTCD standards took place between 1971 and 1975, with most done by the end of 1973, so for two years drivers still had to use the old and new. Yellow was adopted because it was already the standard color of warning signs, and because it was easy to teach drivers to associate yellow lines with dividing opposing traffic and white lines with dividing traffic in the same direction. In turn, this simple mnemonic device greatly reduced head-on collisions and improved road traffic safety.
The major downside to the MUTCD white-yellow system is that yellow has slightly less contrast than white, especially at night, so for maximum contrast, bright yellow—and highly toxic—lead chromate was used to paint yellow lines through the end of the 20th century. As a result, U.S. transportation workers must take special precautions when disturbing or removing yellow lane markings.
In England, the idea of painting a center white line was first experimented with in 1921 in Sutton Coldfield, Birmingham. Following complaints by residents over reckless driving and several collisions, the Sutton Coldfield Corporation decided to paint the line on Maney Corner in the area of Maney.
In 1971, a correspondent for the Sutton Coldfield News wrote an article in the newspaper recalling the event.
The line was put down as an experiment as there were a lot of accidents there, even in the early days of the motor car. The experiment proved to be so successful that the whole country adopted it as a standard road safety device, and later foreign countries put white line on their roads, too.
Today, road markings are used to convey a range of information to the driver spanning navigational, safety and enforcement issues leading to their use in road environment understanding within advanced driver assistance systems and consideration for future use in autonomous road vehicles. .
Mechanical markers 
Mechanical devices may be raised or recessed into the road surface, and either reflective or non-reflective. Most are permanent; some are movable.
- Cat's eye, invented by Percy Shaw in the 1930s, Cat's eyes equip most major routes in the British Isles. They consist of four reflective lenses mounted in a durable white rubber housing, two facing fore and two facing aft. The housing is mounted within a cast iron shoe, which the rubber housing sinks in to when driven over. This provides protection from snow ploughing and allows the lenses to be self-cleaning—they pass a rubber blade when depressed. The lenses are available in a variety of different colours, mainly white, yellow/orange, green, red, and blue.
- Botts' dots (low rounded white dots), named for the California Caltrans engineer Elbert Botts, who invented the epoxy that keeps them glued down, 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. Botts' dots are also used across a travel lane to draw the drivers attention to the road. They are frequently used in this way to alert drivers to toll booths, school zones or other significant reduction of speed limit. They are normally only used in warm climates since snow plows usually remove them along with the snow.
- Rumble strips are commonly used for the same purpose. A rumble strip can be a series of simple troughs (typically 1 cm deep and 10 cm wide) that is ground out of the asphalt. Other alternatives, similar to the Botts' dots, use raised strips, painted or glued to the surface. Uses can be across the travel direction (to warn of hazards ahead) or along the travel direction (to warn of hazards of not staying within a specific lane). Their main way of function is creating a strong vibration when driven over that will alert a driver to various upcoming hazards both by sound and the physical vibration of the vehicle.
- Reflective markers are used as travel lane dividers, to mark the central reservation (median) or to mark exit slip-roads. Incorporating a raised retro-reflective element, they are typically more visible at night and in inclement weather than standard road marking lines. The color of markers varies depending on the country of use; freeways in the United States often use reflectors manufactured to appear white to drivers proceeding in the proper direction of travel, and appear red on the reverse to warn drivers that they are proceeding against the proper direction of travel, creating a danger of a head-on collision. Reflective markers are also referred to as raised pavement markers, road studs, and sometimes (generically) in the UK and Ireland as cat's eye, although this name refers to one particular brand of product. These markers can be used for other purposes such as marking the locations of fire hydrants (blue) or at gates of gated communities to indicate that emergency service vehicles have a code or device that allows them to open the gate. In the United Kingdom and elsewhere, raised markers are used to mark crosswalks (crossings) to assist the blind in crossing streets. In colder climates, reflective markers may 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 allows these to be placed above ground with snowplough-able rails that attempt to protect the reflective components from the snowplough blade.
Non-mechanical markers 
Paint, sometimes with additives such as retrireflective glass beads, is generally used to mark travel lanes. It is also used to mark spaces in parking lots or special purpose spaces for disabled parking, loading zones, or time-restricted parking areas. Colors for these applications vary by locality. Paint is a low-cost marking and has been in widespread use since approximately the early 1950s.
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 along with the application of glass beads for retroreflectivity. After application, the paint dries fairly quickly.
Painted symbols, such as turn-lane arrows or HOV lane markers, are applied manually using stencils.
One of the most common types of road marking based on its balance between cost and performance longevity, thermoplastic binder systems are generally based on one of three core chemistries: hydrocarbons, rosin esters or maleic modified rosin esters (MMRE). Thermoplastic coatings are generally homogeneous dry mixes of binder resins, plasticizers, glass beads (or other optics), pigments, and fillers. Their use has increased over paints mainly due to the performance benefits of increased durability, retro-reflectivity, and a lack of VOC solvents.
Thermoplastic markings are applied using specially designed vehicles. Usually thermoplastic marking mode should apply the professional equipment called road marking machine to coating traffic lines, and the road paint need preheating by a device commonly called preheater. The thermoplastic mix is heated in trucks to about 200 °C (400 °F) before being fed to the application apparatus. This is often a screed box or ribbon gun. Immediately after the thermoplastic has been applied, glass beads are laid onto the hot material so that they embed before the plastic hardens. These beads provide initial retroreflection. As the marking wears during use and the initial beads are lost, the beads mixed with the binder are uncovered, providing long term retroreflectivity. Most thermoplastic is produced in white and yellow colors, but other colors such as red may also be produced.
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 guidance such as turn lanes, HOV lanes, train crossings, pedestrian crossings, taxi lanes, bus lanes, and bike lanes. There are three ways to apply tape:
- Overlay—The 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—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 rollers compress the two together.
- Preformed Thermoplastic—Preformed thermoplastic pavement markings are applied using a propane heat torch and are used primarily because of their durability and cost-effective service life. Cut and ready to position onto an asphalt or concrete pavement surface, the most common applications of preformed thermoplastic pavement markings are found at intersections as transverse markings such as stop lines, legends, crosswalks, arrows, bike lane symbols, and accessibility symbols
Epoxy has been in use since the late 1970s and has gained popularity over the 1990s as the technology has become more affordable and reliable. This material competes directly with plastic with respect to usage and cost.
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.
Country specific information 
In Australia, white lines are generally used both to separate traffic flowing in the same direction and traffic flowing in opposite directions. Double solid white center-lines may not be crossed under any circumstances, unless avoiding an obstruction. Dashed lines may be crossed for overtaking, changing lanes or turning, and also in the case of double-line markings provided the dashed line is on your side of the markings. For this reason dashed lines are usually used to mark multiple lanes traveling in the one direction. Yellow lines along road edges are used nationally to indicate "No Standing" areas not otherwise marked by signs. Solid white lines are also used to indicate kerbside parking, pedestrian and bicycle lanes, and other kerbside features. Yellow line markings are also used in areas that receive regular annual snowfall to provide contrast. Double-line markings are used to separate traffic flowing in opposite directions on busy roads.
Solid white lines are used to mark an intersection that a driver must stop at before entering whilst obeying all Right of Way laws. Dashed white lines are used to mark an intersection at which a driver must Give Way. Dashed white lines are also commonly used to indicate turns in intersections and to indicate intersections where a diamond turn is possible (intersections in which two cars traveling in opposite directions turn to the same direction-of-travel as each other without coming into contact).
Materials used are waterborne paint, thermoplastics, and cold applied plastic (PMMA), all with glass bead. Bead is generally 1mm for longitudinal marking. Currently moving to performance specified contracts with the primary performance indicator being retro-reflectivity measured with 30 metre geometry instruments. Intervention levels vary generally from 100 - 150 mcd/lux/m2.
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Generally speaking, Canadian pavement marking standards are consistent with those used throughout the United States.
Yellow lines are used to separate traffic moving in opposite directions, and white lines are used to separate traffic moving in the same direction, and on the shoulders of paved roads. On one-directional roads, a yellow line appears on the left shoulder, and a white line on the right shoulder. Passing rules are denoted by dashed lines as in the United States. Orange painted lines are sometimes used when the direction of the road is altered temporarily for construction projects. However, the colour scheme was reversed before 1971, when white formerly used to denote the separation of opposing traffic, and yellow lines, when used, to denote the separation of the paved road from the right-hand shoulder.
Broken lines that are wider and closer together than regular broken lines are called continuity lines. Continuity lines on the left side of a lane denote that the lane is about to end and that motorists must soon merge left. Continuity lines on the right mean that the lane will continue, but traffic may merge into it ahead.
In some areas, reflective markers (cat's eyes) recessed into the pavement are used, especially approaching curves in the road.
Ontario has several pavement marking test areas located in various parts of the province. Perhaps the most well-known location is the eastbound lanes of Highway 401 near Belleville. Other test sites are located on the westbound lanes on Highway 417, east of Ottawa, Highway 60 West of Renfrew, Highway 28 east of Bancroft, Highway 69 North of Honey Harbour and on Highway 37, South of Tweed. Pavement marking manufacturers from around the world supply a variety of materials for these sites to have their products evaluated and approved for use on provincial highways.
India and Pakistan 
White lines separate lanes in same direction and yellow lines separate lanes in different directions.[dubious ]
Japan uses a scheme similar in to North American markings. White always separates traffic in the same direction or indicates traffic in the same direction can use a buffered area that is striped in crosshatch patterns such as at right turns on two-way roads since Japan is a country that has left-side driving.
White is also used on divided expressways with a solid raised center divider, two-lane expressways where poles are the only physical barrier between opposing directions of travel always have yellow either side of the row of poles. White is between the yellow striping and the poles.
White is also used to denote passing allowed on other two-lane roads. Yellow indicates no passing is allowed. On all roads, yellow stripes are always solid.
On expressways where there are many sharp turns and curves, seen especially in the largest cities, a yellow line indicates no passing between lanes, as follows:
- Solid yellow beside solid white: no entry permitted from the lane the stripe is next to, but passing is permitted with caution.
- Solid yellow beside broken white: passing is permitted from the side with the broken white line, but not from the side with the yellow line.
- Solid yellow line alone: passing prohibited from either lane, used on very tight curves and in tunnels.
Other markings include in the cities, destination and exit names painted in the lanes, which is done due to the very close proximity of exits, where in many cases it would be impractical to put up many overhead signs, although these are often seen approaching exits, a curved or slanted arrow points to the side of the expressway the exit will be on. A straight arrow following characters indicates the destination of the expressway.
Where a solid white line appears between lanes, passing is generally allowed but with caution.
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. The New Zealand convention followed the USA MUTCD convention common between 1961 and the early seventies.
In Norway, yellow lines are used to separate traffic moving in opposite directions and on the left shoulders of paved roads, and white lines are used to separate traffic moving in the same direction, and on the right shoulders of paved roads. Most other European countries use white lines for all these types of lines.
Hong Kong 
Road markings in Hong Kong is basically identical with the United Kingdom, with longer dashed white lines to indicate lanes of opposing traffic, and shorter dashed white lines for lanes in the same direction. Solid double white lines are used to indicate that drivers are not permitted to change lanes. A solid white line with a broken white line indicates that crossing the line is allowed from the lane closer to the broken line. Double solid white lines are in place in all tunnels and underpasses.
As in the UK, solid yellow lines are painted along the kerbside to indicate that no parking is allowed, with double solid yellow lines meaning no parking is allowed at all times. Zig-zag lines are used on both ends of zebra crossings. Road studs are also used as in the UK.
United Kingdom 
During the World War II the Pedestrians Association lobbied for the government to make it safer for pedestrians to walk during the black out. As a result white lines were painted on the sides of the road and pedestrians were allowed to use a small torch.
In the U.K. The first "white line" road markings appeared on a number of dangerous bends on the London-Folkeston road at Ashford, Kent, in 1914, and during the 1920s the rise of painted lines on UK roads grew dramatically. In 1926 official guidelines were issued by the Ministry of Transport that defined where and how white lines on roads should be used. A broken white line in the direction of travel, where the gaps are longer than the painted lines, indicates the centre of the road and that there are no hazards specific to the design and layout of the road, i.e. no turnings, sharp bends ahead etc. A broken white line in which the gaps are shorter than the painted lines indicates an upcoming hazard, the proportion of white to black indicates the degree of hazard i.e. more white means more hazard.[not in citation given]
A double solid white line indicates that the line may not be crossed, overtaking is permitted if it can be performed safely without crossing the line. Solid lines can be crossed in certain specific conditions (entering premises, overtaking a stationary vehicle, overtaking a vehicle, pedal cycle or horse travelling at less than 10 mph, or when directed to do so by a police officer). A solid white line with a broken white line parallel to it indicates that crossing the line is allowed for traffic in one direction (the side closest to the broken line) and not the other.
Solid white lines are also used to mark the outer edges of a road.
A double yellow line (commonly known as just a "Double Yellow") next to the kerb means that no parking is allowed at any time, whilst a single yellow line is used in conjunction with signs to denote that parking is restricted at certain times. Double and single red lines mean that stopping is not allowed at any time or between certain times respectively.
On many roads in the UK, retro-reflective road studs, including those known as "cat's eyes" when referring to the Halifax type road stud, are placed in the road. These devices reflect the light from a car's headlights back towards the driver in order to highlight features of the road in poor visibility or at night. The colour of road studs differs according to their location. Those defining the division between lanes are white, red road studs are placed along the hard shoulder of motorways, dual carriageways and other roads to mark the left-hand edge of a running lane; and orange road studs are placed along the edge of the central reservation. Green road studs denote slip roads at grade-separated junctions and also road-side lay-bys.
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 its 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, Botts' dots are commonly used to mark lanes on most freeways. A large number of California cities also use Botts' dots on some (or all) major arterial roads. The notable exception is the city of Los Angeles which only uses paint.
In California and Nevada, the reflectors when present are usually the lines, and no paint is used for additional markings. 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, single broken lines mean passing or lane changing is allowed, single solid white lines mean lane changing is discouraged but not prohibited, and double solid white lines mean it is prohibited, as it often is in tunnels. On two-lane roads, a single broken center line means that passing is allowed in either direction, a double solid center line means passing is prohibited in both directions, and the combination of a solid line with a broken line means that passing is allowed only from the side with the broken line and prohibited from the side with the solid line.
Marked 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. In order to maximize the longevity of zebra crossing stripes, they are usually applied to correspond with the portions of the lane on which the wheels of a car are not usually traveling, thereby reducing wear on the markings themselves.
Western Europe 
Several Western European countries reserve white for routine lane markings of any kind, except bus stops and similar things. However, for example Norway has yellow markings separating traffic directions. Many countries use yellow, orange, or red to indicate when lanes are being shifted temporarily to make room for construction projects.
In the Netherlands, Germany, Sweden, and the UK, so-called "naked roads" have been trialled, whereby all visible road markings, kerbs, traffic lights, and signs are removed. When this was tested in Seend, a village in the UK county of Wiltshire, the county council reported that accidents fell by a third, with motorists' speed falling by an average of 5%. It has been suggested that naked roads force drivers to make eye contact with other road users, and that it is this nonverbal communication that is responsible for the reduction of accidents. Other have suggested that road markings, especially with middle marker, make the road look like a main road, triggering faster and more relaxed driving, while no marking makes the road look like a lower quality road.
See also 
- Cranson, Jeff (November 2, 2011). "Inventor of Highway Centerline Receives International Honor" (Press release). Michigan Department of Transportation. Retrieved January 8, 2012.
- Staff (May 10, 2006). "Edward N. Hines (1870-1938)". Michigan Transportation Hall of Fame. Michigan Department of Transportation. Retrieved September 3, 2007.
- "Goodbye, Yellow Line" (Editorial, PDF). The Oregonian (Portland, OR). November 17, 1954. p. 4M.
- "Traffic Marks on Country Roads". The Literary Digest: 29. October 23, 1920. OCLC 5746986.
- Kulsea, Bill; Shawver, Tom (1980). Making Michigan Move: A History of Michigan Highways and the Michigan Department of Transportation. Lansing, MI: Michigan Department of Transportation. p. 10.
- Federal Highway Administration (1977). America's Highways, 1776–1976: A History of the Federal-Aid Program (PDF). Washington, DC: US Government Printing Office. p. 127. OCLC 3280344.
- Staff (May 9, 2006). "K. I. Sawyer (1884-1944)". Michigan Transportation Hall of Fame. Michigan Department of Transportation. Retrieved February 2, 2010.
- Rexford, Peter V. (December 4, 1954). "Earlier Line" (Letter to the Editor, PDF). The Oregonian (Portland, OR). p. 3M.
- "Noted Deputy Gives up Post" (PDF). The Oregonian (Portland, OR). June 29, 1947. p. 22.
- King, John G. (1965). A History of the Office of Multnomah County Sheriff (B.A. thesis). Lewis & Clark College. OCLC 43008710.
- Kneidek, Tony (March 11, 1978). "Sheriff Department History Full of Color" (PDF). Gresham Outlook. p. 14.
- Lansing, Jewel; Leeson, Fred (2012). Multnomah: The Tumultuous Story of Oregon's Most Populous County. Corvallis, OR: Oregon State University Press. p. 63. ISBN 978-0-87071-665-2.
- Starr, Shannon (April 6, 2002). "Woman Credited for Highway Center Lines: Dr. June McCarroll of Indio Will Be Honored with Signs on Interstate 10". The Press-Enterprise (Riverside, CA). p. B3.
- Guzman, Richard (April 24, 2002). "Caltrans will honor local motorist who drew the line". The Desert Sun (Palm Springs, cA). p. B1.
- "White, or Else" (Editorial, PDF). The Oregonian (Portland, OR). February 26, 1958. p. 3M.
- Center for Environmental Excellence. "Section 5.5, Pavement Recycling". Compendium of Environmental Stewardship Practices in Construction and Maintenance. American Association of State Highway and Transportation Officials.
- Jones, Douglas V. (1994). The Royal Town of Sutton Coldfield: A Commemorative History. Sutton Coldfield: Westwood Press. ISBN 0-9502636-7-2.[page needed]
- Kheyrollahi, A.; Breckon, T.P. (2012). "Automatic Real-time Road Marking Recognition Using a Feature Driven Approach" (PDF). Machine Vision and Applications (Springer) 23 (1): 123–133. doi:10.1007/s00138-010-0289-5. Retrieved April 8, 2013.
- '"The Hidden Persuaders". Contractor 30 (9). October 2007.
- "Thermoplastic Spraying Road Marking Paint, Reflective ability, Fast drying".
- Bevers, Cameron. "Frequently Asked Questions About Ontario Highways". The King's Highway. Self-published. Retrieved January 8, 2013.[unreliable source]
- "Pavement Markings". Ontario Driver's Handbook (Ministry of Transportation of Ontario). Retrieved January 6, 2009.
- "Pavement Marking Innovations Paving the Way for Progress". MTO Road Talk (Ministry of Transportation of Ontario) 10 (1). Retrieved January 6, 2009.
- Staff (2000). "Chapter 5: For All Drivers, White Lines and Traffic Lanes". Road Users' Code. Hong Kong Transport Department. OCLC 45968644. Retrieved January 8, 2018.
- "The History of the Pedestrians Association". Living Streets. Retrieved February 27, 2010.
- Anon. "History of Road Markings and How They Were First Designed". Traffic signs and meanings (Traffic signs and meanings 2000-2010). Retrieved January 29, 2010.
- Manual on Uniform Traffic Control Devices (Revision 2, 2003 ed.). Federal Highway Administration. 2003. ISBN 9780935403817.
- "Can 'Naked Roads' Kill Speed?". BBC News. Retrieved May 19, 2007.
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