For other uses, see Asphalt (disambiguation). Note: The terms bitumen and asphalt are mostly interchangeable, Commercial Paving Company in East Rand except where asphalt is used as a shorthand for asphalt concrete. Natural bitumen from the Dead Sea Refined asphalt The University of Queensland pitch drop experiment, demonstrating the viscosity of asphalt
The primary use (70%) of asphalt Asphalt Sealcoating Companies is in road construction, where it is used as the glue or binder mixed with aggregate particles to create asphalt concrete. Its other main uses are for bituminous waterproofing products, including production of roofing felt and for sealing flat roofs.
Naturally occurring asphalt is sometimes specified by the term “crude bitumen”. Commercial Paving Company Its viscosity is similar to that of cold molasses while the material obtained from the fractional distillation of crude oil boiling at 525 °C (977 °F) is sometimes referred to as “refined bitumen”. The Canadian province of Alberta has most of the world’s reserves of natural asphalt in the Athabasca oil sands, which cover 142,000 square kilometres (55,000 sq mi), an area larger than England.
The word “asphalt” is derived from the late Middle English, in turn from French asphalte, based on Late Latin asphalton, asphaltum, which is the latinisation of the Greek ἄσφαλτος (ásphaltos, ásphalton), a word meaning “asphalt/bitumen/pitch” which perhaps derives from ἀ-, “without” and σφάλλω (sfallō), “make fall”. Asphalt Road Construction Companies the first use of asphalt by the ancients was in the nature of a cement for securing or joining together various objects, and it thus seems likely that the name itself was expressive of this application. Specifically, Herodotus mentioned that bitumen was brought to Babylon to build its gigantic fortification wall. From the Greek, the word passed into late Latin, and thence into French (asphalte) and English (“asphaltum” and “asphalt”). In French, the term asphalte is used for naturally occurring asphalt-soaked limestone deposits, and for specialised manufactured products with fewer voids or greater bitumen content than the “asphaltic concrete” used to pave roads.
In Australian English, “bitumen” is often used as the generic term for road surfaces.
See also: Asphaltene
The components of asphalt include four main classes of compounds:
Bituminous outcrop of the Puy de la Poix, Clermont-Ferrand, France
Commercial Paving Company in East Rand ?Thru lanes indicated by arrows on California CR G4 (Montague Expressway) in Silicon Valley.
In the context of traffic control, a lane is part of a roadway (carriageway) that is designated for use by a single line of vehicles, to control and guide drivers and reduce traffic conflicts. Most public roads (highways) have at least two lanes, one for traffic in each direction, separated by lane markings. On multilane roadways and busier two-lane roads, lanes are designated with road surface markings. Major highways often have two multi-lane roadways separated by a median.
Some roads and bridges that carry very low volumes of traffic are less than 15 feet (4.6 m) wide, and are only a single lane wide. Vehicles travelling in opposite directions must slow or stop to pass each other. In rural areas, these are often called country lanes. In urban areas, alleys are often only one lane wide. Urban and suburban one lane roads are often designated for one-way traffic.
Lane capacity varies widely due to conditions such as neighboring lanes, lane width, elements next to the road, number of driveways, presence of parking, speed limits, number of heavy vehicles and so on – the range can be as low as 1000 passenger cars / hour to as high as 4800 passenger cars /hour but mostly falls between 1500 and 2400 passenger cars / hour.The Ontario Highway 401 in the Greater Toronto area, with 17 travel lanes in 6 separate carriageways visible in the midground. Turning lane on the Rodovia BR-101 (Brazil) Play media Changing lanes, Gothenburg, Sweden Transfer lanes, connecting surface collector lanes with through lanes between two tunnels A left-turn merging lane in Germany, needing explanation by a crafted sign These usages lead to the phrases life in the slow lane and life in the fast lane, used to describe relaxed or busy lifestyles, respectively and used as the titles of various books and songs.
While in general, wider lanes are associated with a reduction in crashes, in urban settings both narrow (less than 2.8 m) and wide (over 3.1~3.2 m) lanes increase crash risks. Wider lanes (over 3.3~3.4m) are associated with 33% higher impact speeds, as well as higher crash rates. Carrying capacity is also maximal at a width of 3 to 3.1 metres (9.8 to 10.2 ft), both for motor traffic and for bicycles. Pedestrian volume declines as lanes widen, and intersections with narrower lanes provide the highest capacity for bicycles. As lane width decreases, traffic speed diminishes.
Advocates for safety of people walking and people on bikes, and many new urbanists disagree with traditional thinking in traffic engineering, saying that safety and capacity are not adversely impacted by reducing lanes widths to as little as 10 feet (3.0 m). Moreover, wider travel lanes also increase exposure and crossing distance for pedestrians at intersections and midblock crossings.assumed widths and heights in road design for Europe (in meters)
The widths of vehicle lanes typically vary from 9 to 15 feet (2.7 to 4.6 m). Lane widths are commonly narrower on low volume roads and wider on higher volume roads. The lane width depends on the assumed maximum vehicle width with an additional space to allow for lateral motion of the vehicle.
The maximum truck width had been 96 inches (2.438 m) in the Code of Federal Regulations of 1956 which matches with the width of eight-foot for shipping containers. This had been increased to 102 inches (2.591 m) in 1976 which explicitly states to be read as the slightly larger metric 2.6 metres (102.36 in) width respecting international harmonization. The same applies to standards in Europe which had increased the allowable size of road vehicles with a current maximum of 2.55 metres (100.39 in) for most trucks and allowing 2.6 metres (102.36 in) for refrigerator trucks. The minimum extra space had been 0.20 metres (7.87 in) and it is currently assumed to be at least 0.25 metres (9.84 in) on each side. For roads with a lower amount of traffic it is allowed to build the second or third lane in the same direction to an assumed lower width for cars like 1.75 metres (68.90 in), however this is not recommended as a design principle for new roads as changes in the amount of traffic could make for unnecessarily increased risks in the future.
The Interstate Highway standards for the U.S. Interstate Highway System uses a 12-foot (3.7 m) standard for lane width, while narrower lanes are used on lower classification roads. In Europe, as laws and road width vary by country, the minimum widths of lanes is generally between 2.5 to 3.25 metres (8.2 to 10.7 ft). The federal Bundesstraße interurban network in Germany defines a minimum of 3.5 metres (11 ft 6 in) for each lane for the smallest two lane roads with an additional 0.25 metres (9.84 in) on the outer sides and shoulders being at least 1.5 metres (59.06 in) on each side. A modern Autobahn divided highway will have two lanes per direction which are 3.75 metres (12 ft 4 in) wide with an additional clearance of 0.50 metres (19.69 in) on each side, while three lanes per direction are set at 3.75 metres (12 ft 4 in) for the rightmost lane and 3.5 metres (11 ft 6 in) for the other lanes. Urban access roads and roads in low-density areas may have lanes as small as 2.75 metres (9 ft 0 in) in width per lane with shoulders being at least 1 metre (3 ft 3 in) wide.Main article: Road surface marking A typical rural American freeway (Interstate 5 in the Central Valley of California). Notice the yellow line on the left, the dashed white line in the middle, and the solid white line on the right. Also note the rumble strip to the left of the yellow line.
Painted lane markings vary widely from country to country. In the United States, Canada, Mexico, Honduras, Puerto Rico, Virgin Islands and Norway, yellow lines separate traffic going opposite directions and white separates lanes of traffic traveling the same direction, but such is not the case in many European countries.
Lane markings are mostly lines painted on the road by a road marking machine, which can adjust the marking widths according to the lane type.
Traffic reports in California often refer to accidents being "in the number X lane." The California Department of Transportation (Caltrans) assigns the numbers from left to right. The far left passing lane is the number 1 lane. The number of the slow lane (closest to freeway onramps/offramps) depends on the total number of lanes, and could be anywhere from 2 to 8.
For much of human history, roads did not need lane markings because most people walked or rode horses at relatively slow speeds. Another reason for not using lane markings is that they are expensive to maintain.
When automobiles, trucks, and buses came into widespread use during the first two decades of the 20th century, head-on collisions became more common.
Without the guidance provided by lane markings, drivers in the early days often erred in favor of keeping closer to the middle of the road, rather than risk going off-road into ditches or trees. This practice often left inadequate room for opposing traffic.
The history of lane markings is connected to the mass automobile construction in Detroit. It resulted in the formation of the first Road Commission of Wayne County, Michigan in 1906 which was trying to make roads safer (Henry Ford served on the board in the first year). The commission would order the construction of the first concrete road in 1909 (the Woodard Avenue in Detroit) and it conceived the centerline for highways in 1911. Hence the chairmen of the Road Commission, Edward N. Hines is widely credited as the inventor of line markings.
The introduction as a common standard is connected to June McCarroll, a physician in Indio, California who started experimenting with painting lines on roads in 1917 after she was run off a highway by a truck driver. In November 1924, after years of lobbying by Dr. McCarroll and her allies, California officially adopted a policy of painting lines on its highways. A portion of Interstate 10 near Indio has been named the Dr. June McCarroll Memorial Freeway in her honor.black center line on an Autobahn in Germany (late 1930s)
The first lane markings in Europe were painted at an accident hotspot in the small town of Sutton Coldfield near Birmingham, England in 1921. The success of this experiment made its way to other hotspots and later standardization of white paint for line markings in Great Britain.
The first lane markings in Germany were used in Berlin in 1925 using white paint for line markings and road edge markings. When the standard for the new autobahn network was conceived in the 1930s it mandated the usage of black paint for the center line for each carriageway as black was better visible on the bright surface of the concrete roads.
By 1939, lane markings had become so popular that they were officially standardized throughout the United States. The concept of line markings spread throughout the world becoming standard for most roads. Originally the lines were drawn manually with normal paint which would bleach out quickly. After the war, the first machines for line markings were invented and a plastic strip was becoming standard in the 1950s which led to gradually find line markings on all roads.Main article: Right- and left-hand traffic
SealcoatStandard design on a wide median. Stylized depiction of the design in Grand Haven, Michigan, at US 31 and Robbins Road (north to the right), showing the additional area necessary to make a turn on a narrow median. 43°2′40.18″N 86°13′12.57″W / 43.0444944°N 86.2201583°W / 43.0444944; -86.2201583 (US 31 at Robbins Road, Grand Haven, Michigan)
A Michigan left is an at-grade intersection design which replaces each left turn with a U-turn and a right turn. The design was given the name due to its frequent use along roads and highways in the U.S. state of Michigan since the late 1960s. In other contexts, the intersection is called a median U-turn crossover or median U-turn. The design is also sometimes referred to as a boulevard left, a boulevard turnaround, a Michigan loon or a "ThrU Turn" intersection.Two versions of signs posted along an intersecting road or street at an intersection. Top: most commonly used; Bottom: lesser-used variant.
The design occurs at intersections where at least one road is a divided highway or boulevard, and left turns onto—and usually from—the divided highway are prohibited. In almost every case, the divided highway is multi-laned in both directions. When on the secondary road, drivers are directed to turn right. Within 1⁄4 mile (400 m), they queue into a designated U-turn (or cross-over) lane in the median.
When traffic clears they complete the U-turn and go back through the intersection. Additionally, the U-turn lane is designed for one-way traffic. Similarly, traffic on the divided highway cannot turn left at an intersection with a cross street. Instead, drivers are instructed to "overshoot" the intersection, go through the U-turn lane, come back to the intersection from the opposite direction, and turn right.
When vehicles enter the cross-over area, unless markings on the ground indicate two turning lanes in the cross-over, drivers form one lane. A cross-over with two lanes is designed at high-volume cross-overs, or when the right lane turns onto an intersecting street. In this case, the right lane is reserved for vehicles completing the design. Most crossovers must be made large enough for semi-trailer trucks to complete the crossover. This large cross-over area often leads to two vehicles incorrectly lining up at a single cross-over.
The maneuver forces the driver to quickly merge into the extreme left lane to complete the turn, usually from a complete stop. The turning vehicle is potentially a hazard and may cause a disruption in the flow of traffic in the left lane.
When the median of a road is too narrow to allow for a standard Michigan left maneuver, a variation can be used which widens the pavement in the opposite direction of travel. This widened pavement is known as a "bulb out" or a "loon" (from the pavement's aerial resemblance to the aquatic bird). Such a design is sometimes referred to as a Michigan loon; in Utah, as a ThrU Turn, which is a portmanteau combining the terms "Through" (the intersection, followed by a) "U Turn".
In 2013, Michigan lefts were installed in Alabama for the first time, in several locations along heavily traveled U.S. Route 280 in metro Birmingham.
Tucson, Arizona, began introducing Michigan lefts in 2013, at Ina/Oracle and Grant/Oracle. Their reception has been mixed.
The design is relatively common in New Orleans, Louisiana, and its suburb Metairie, where city boulevards may be split by streetcar tracks, and suburban thoroughfares are often split by drainage canals. Some intersections using this design are signed similarly to those in Michigan, but with more descriptive text, however in some cases the only signage is "No Left Turn" and drivers are left to figure it out for themselves.
Since the redevelopment of the intersection between University Boulevard (MD 193) and Colesville Road (US 29) in Silver Spring, Maryland, a Michigan left has been used to increase efficiency of traffic through an otherwise underdeveloped and congested intersection. Due to its proximity to the Capital Beltway, heavy traffic is handled more safely and efficiently.A typical Michigan left layout: Telegraph Road (US 24) at Warren Road near Detroit, showing Michigan lefts 42°20′28″N 83°16′23″W / 42.341°N 83.273°W / 42.341; -83.273 (US 24 (Telegraph Road) at Warren Road, Dearborn, Michigan)
The Michigan Department of Transportation first used the modern design at the intersection of 8 Mile Road (M-102) and Livernois Avenue (42°26′46″N 83°08′28″W / 42.4461°N 83.141°W / 42.4461; -83.141 (M-102 (8 Mile Road) at Livernois Avenue)) in Detroit in the early 1960s. The increase in traffic flow and reduction in accidents was so dramatic (a 30–60% decrease) that over 700 similar intersections have been deployed throughout the state since then.
North Carolina has been implementing Michigan lefts along US 17 in the southeastern part of the state, outside Wilmington. In 2015, a Michigan left was constructed at the intersection of Poplar Tent Road and Derita Road in the Charlotte suburb of Concord.
Columbus, Ohio introduced a Michigan left at the intersection of SR 161 and Strawberry Farms Boulevard in 2012. Reception has been mixed with several accidents occurring per year.
At least two Michigan lefts have existed in Texas. One was located at the intersection of Fondren Road and Bellaire Boulevard in Houston from the 1980s through 2007, when it was replaced with conventional left-turn lanes. Another was built in mid-2010 in Plano at the intersection of Preston Road and Legacy Drive. In January 2014, the city announced plans to revert the turn to a traditional intersection as a result of drivers' confusion. A section of State Highway 71 east of Austin-Bergstrom International Airport at FM 973 in Austin, Texas did have a signalized Michigan U-turn which was constructed in 2014—this was a temporary fix until the SH71 tollway over SH130 (including the re-routing of FM973) was completed in early 2016. There are multiple Michigan left turns currently being used along US 281 north of Loop 1604 in San Antonio. These were adopted as a short-term solution for traffic issues as development expanded north, but will likely be phased out as US 281 is elevated.
The city of Draper, Utah, a suburb of Salt Lake City, announced in 2011 that it would be building Utah's first "ThrU Turn" at the intersection of 12300 South and State Street, just off Interstate 15 through Salt Lake County. Construction began in summer 2011 and was completed in fall 2011. Other similar intersections were implemented in South Jordan and Layton.
In Australia, where traffic drives on the left, the Victorian state government introduced the "P-turn", similar to the Michigan left, at one intersection in 2009. This requires right-turning vehicles to turn left then make a U-turn. As of May 2015, the intersection in the southeastern Melbourne suburb of Frankston remains the only one of its kind in the state, and local residents have called for its removal.
A similar style P-turn is used in the junction of the A4 Great West Road and A3002 Boston Manor Road in Brentford, England.
The design has been proposed in Toronto, Ontario, to relieve motorists who wish to make a left-turn on roadways which will contain a proposed streetcar line by the Transit City project.
In Ottawa, Ontario, a Michigan left exists to proceed from Riverside Drive, northbound, to Bank Street northbound.
Another Michigan left exists in Windsor, Ontario, on Huron Church Road, just north of the E.C. Row Expressway, where a narrow-median variant put in place years ago is now seldom used due to the realignment of the expressway in conjunction with the construction of the Herb Gray Parkway.
In Mexico, Guadalajara has a grade-separated variation of this setup in the intersection of Mariano Otero Avenue and Manuel Gómez Morín Beltway (20°37′50″N 103°26′06″W / 20.630666°N 103.434981°W / 20.630666; -103.434981). Traffic flowing through Mariano Otero is routed through an overpass above the beltway, with two access roads allowing right turn on all four possible directions; the U-turns, meanwhile, are built underneath the beltway and allow the left turn from Mariano Otero avenue to the beltway. U-turn intersections are very common throughout Mexico, particularly in Mexico City.
Brazil is also known to utilize this setup especially in São Paulo.
This is the design at some busy junctions in Hong Kong. In Hong Kong Island examples include the junction of Fleming Road and Harbour Road in Wan Chai North, and the junction of Hennessey Road and Canal Road Flyover in Wong Nai Chung. In Kowloon this design exists between Cheong Wan Road and Hong Chong Road/Salisbury Road.
The capital city of Angola, Luanda, makes widespread use of a simplified variant of this type of intersection on its two- and three-lane, median-separated throughways instead of using traffic lights. Larger junctions use this intersection type instead of much more costly grade-separated interchanges.
This type of intersection configuration, as with any engineered solution to a traffic problem, carries with it certain advantages and disadvantages and has been subject to several studies.
Studies[by whom?][when?] have shown a major reduction in left-turn collisions and a minor reduction in merging and diverging collisions, due to the shifting of left turns outside the main intersection[clarification needed]. In addition, it reduces the number of different traffic light phases, significantly increasing traffic flow. Because separate phases are no longer needed for left turns, this increases green time for through traffic. The effect on turning traffic is mixed. Consequently, the timing of traffic signals along a highway featuring the design is made easier by the elimination of left-turn phases both on that highway and along intersecting roadways contributing to the reduction of travel times and the increased capacity of those roadways.
It has been shown to enhance safety to pedestrians crossing either street at an intersection featuring the design since they only encounter through traffic and vehicles making right turns. The left-turning movement, having been eliminated, removes one source of potential vehicle-pedestrian conflict. One minor disadvantage of the Michigan left is the extra distance required for the motorist to drive. Sometimes the distance to the turnaround is as far away as 1⁄4 mile (400 m) past the intersection. This design leads to each motorist driving an additional 1⁄2 mile (800 m) to make a left turn. It also results in left-turning vehicles having to stop up to three times in the execution of the turn.