Science Fair Project Encyclopedia
The word lane has two meanings:
- A narrow road, usually lacking a shoulder or a median. The word is typically applied to roads in the countryside, but can also be applied to urban streets like Drury Lane in London. Some places, like the U.S. state of Nevada, like to apply the term to certain arterial roads.
- The area of a street or road marked by white or yellow lines, in which motorists maintain a consistent direction of travel. This is the more commonly used meaning in everyday English speech and is the one elaborated upon here.
Most countries with a significant number of automobiles maintain lanes on their roads, and strictly enforce laws requiring drivers to stay in their lanes as much as possible (as opposed to randomly "drifting" or "weaving" which is common in lane-less countries like Egypt). In many countries, a prolonged inability to stay in one's lane is considered to be a sign of drunk driving and may lead to a citation for a traffic violation, or even an arrest.
Types of lanes
- A through lane or traffic lane is the default type of lane for through traffic. At intersections, these may be indicated by arrows on the pavement pointing straight ahead.
- A fire lane is the area next to a curb, which is reserved for firefighting equipment in the event of a fire. Parking in these areas, usually marked by red lines, often warrants a parking ticket .
- A loading lane is an area next to a curb, which is reserved for loading and unloading passengers. It may be marked by a "LOADING ONLY" sign or a yellow or white curb.
- A passing lane is often provided on steep mountain grades, in order to allow smaller vehicles to pass larger, slower ones. This is sometimes called a climbing lane if on the uphill side. Passing lanes may also be provided on long stretches of other roadway. On two-lane roads, passing in the lane of oncoming traffic is sometimes allowed given a long enough straightaway, if the broken line is on the normal side of travel.
- An auxiliary lane along a highway or motorway connects slip roads, with the entrance ramp or acceleration lane from one interchange leading to the exit ramp or deceleration lane of the next.
- The emergency lane of a road (also known as the breakdown lane or shoulder) is reserved for breakdowns, and for emergency vehicles. Often, especially in rural areas, these lanes deliberately have ruts cut in them, in order to warn drivers that they are leaving the roadway. This feature is especially important in the circumstance that a driver falls asleep at the wheel.
- An HOV lane or carpool lane is reserved for carpooling. It may be marked with a diamond icon every few hundred feet (hence the nickname "diamond lane"), or separated from other lanes by double broken white lines, a continuous pair of double yellow lines, or just a single broken white line.
- A turn lane is set aside for slowing down and making a turn, so as not to disrupt traffic. At a full intersection with a traffic light, turn lanes are used more to hold traffic until the light changes.
- A bike lane is a half-lane reserved for bicycling. This may be indicated by a bicycle icon, the word "BIKE" (or its local equivalent), or both.
- A bus lane is reserved for buses, especially if there is an overhead catenary for electric buses. In some countries, bus lanes may also be used by taxis, bicycles and motorbikes.
- A reversible lane is one which uses overhead lights, signs, poles or barriers to indicate the current direction of travel it is to be used for. Typically, it is used at rush hour to accommodate extra traffic, and at other times as a center turn lane. In between, there is approximately one hour where no traffic is allowed. While the idea is very simple, the term suicide lane became a common slang description for this design, because many people did not pay attention to their driving or the lights. Because of their history of numerous accidents and collisions, reversible lanes are rarely used now. However, there are some functional examples on the river bridges just east of downtown Los Angeles which use lights only and nothing else to indicate the direction of traffic for each lane. Some places, like Hawaii, call these lanes contraflow lanes and enforce them with plastic poles which are manually rearranged by work crews before and after rush hour.
In general, broken lines mean passing is allowed, single solid lines mean it is discouraged, and double solid lines mean it is prohibited, as it often is in tunnels.
In most countries, yellow is used down the center to denote oncoming traffic is across the line. On a divided road (or dual carriageway or twinned road), a median (central reservation) segregates the traffic. White is usually used to separate traffic going in the same direction. Some places have this reversed.
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. New Zealand uses a dashed white line to indicate when passing against opposing traffic is allowed on two-lane roads and to separate lanes going in the same direction, with chaotic results.
In all countries, private roads and parking lots often ignore the rules altogether.
In the U.K., zig-zag lines painted on the street mark a pedestrian crossing area. In the U.S., such areas (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.
Lines are usually painted with highly reflective paint, often with tiny clear beads that reflect light straight back like a raindrop. Glass and now plastic reflectors are often embedded next to the lines for improved nighttime visibility . 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).
Frequently, the "back" of the white reflectors are red, to indicate the wrong direction of travel for anyone who enters the wrong way.
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. California cities also use Botts dots on 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.
For much of human history, roads generally did not have lane markings. This was probably because most of the time, pedestrians, equestrians, and horse-drawn vehicles all moved slower than 10 miles per hour most of the time, and thus everyone had adequate time to swerve around each other. Photos of the streets of any major city from the 19th century show all three types of traffic freely intermixed with each other. Another reason for not using lane markings was that they are expensive to maintain.
However, when automobiles, trucks, and buses came into widespread use during the first two decades of the 20th century, it became common for drivers to get into head-on collisions, or to literally run each other off the road.
Anyone who has ever driven a vehicle is aware that it takes long practice to develop a sense of where the edges of one's vehicle are in relation to the road's edges and to other vehicles. Without the feedback provided by lane markings, novice 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. Unfortunately, this practice often left inadequate room for opposing traffic to go by.
The invention of lane markings is generally credited to an American physician, Dr. June McCarroll. Based in Indio, California, McCarroll started experimenting with painting lines on roads in 1924 after she was personally run off a highway by an inexperienced truck driver. By 1939, lane markings had become so popular that they were officially standardized throughout the United States, and were soon in use all over the world.
A portion of Interstate 10 near Indio has been named the Dr. June McCarroll Memorial Freeway in her honor.
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