Traffic
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Traffic comprises
Traffic laws govern and regulate traffic, while rules of the road include traffic laws and
Traffic is formally organized in many jurisdictions, with marked
Organization typically produces a better combination of
.Etymology and types
The word traffic originally meant "trade" (as it still does) and comes from the Old Italian verb trafficare and noun traffico. The origin of the Italian words is unclear. Suggestions include
Rules of the road
Rules of the road and
As a general rule, drivers are expected to avoid a collision with another vehicle and pedestrians, regardless of whether or not the applicable rules of the road allow them to be where they happen to be.[5][6]
In addition to the rules applicable by default, traffic signs and traffic lights must be obeyed, and instructions may be given by a police officer, either routinely (on a busy crossing instead of traffic lights) or as road traffic control around a construction zone, accident, or other road disruption.
Directionality
Traffic heading in inverse ways ought to be isolated so as to not hinder each other's way. The most essential guideline is whether to utilize the left or right half of the street.
Traffic regulations
In many countries, the rules of the road are codified, setting out the legal requirements and
In
In
Organised traffic
Passage priority (right of way)
Vehicles often come into conflict with other vehicles and pedestrians because their intended courses of travel intersect, and thus interfere with each other's routes. The general principle that establishes who has the right to go first is called "right of way" (spelled without hyphens and distinct from "right-of-way" spelled with hyphens), or "priority". It establishes who has the right to use the conflicting part of the road and who has to wait until the other does so.
Signs, signals, markings and other features are often used to make priority explicit. Some signs, such as the stop sign, are nearly universal. When there are no signs or markings, different rules are observed depending on the location. These default priority rules differ between countries, and may even vary within countries. Trends toward uniformity are exemplified at an international level by the Vienna Convention on Road Signs and Signals, which prescribes standardised traffic control devices (signs, signals, and markings) for establishing the right of way where necessary.
Crosswalks (or pedestrian crossings) are common in populated areas, and may indicate that pedestrians have priority over vehicular traffic. In most modern cities, the
Uncontrolled traffic
Uncontrolled traffic comes in the absence of
Intersections have no signals or signage, and a particular road at a busy intersection may be dominant – that is, its traffic flows – until a break in traffic, at which time the dominance shifts to the other road where vehicles are queued. At the intersection of two perpendicular roads, a traffic jam may result if four vehicles face each other side-on.
Aviation
In aviation, right-of-way rules are established over the principle that the least maneuverable aircraft takes priority. In the United States, the Code of Federal Regulations ranks air traffic in the following passage order:[7]
- Any aircraft in distress
- Air balloon
- Glider
- Airship
- An aircraft towing or refueling other aircraft has the right-of-way over all other engine-driven aircraft
- weight-shift-control aircraft, airplane, and rotorcraft
In addition, head-on approaching aircraft shall alter course to the right. An aircraft being overtaken has the right-of-way. A landing aircraft has the right-of-way over other surface-operating aircraft.[7]
Turning
Drivers often seek to turn onto another road or onto
This will usually mean that turning traffic must stop and wait for a breach to turn, and this might cause inconvenience for drivers that follow them but do not want to turn. This is why dedicated lanes and protected traffic signals for turning are sometimes provided. On busier intersections where a protected lane would be ineffective or cannot be built, turning may be entirely prohibited, and drivers will be required to "drive around the block" in order to accomplish the turn. Many cities employ this tactic quite often; in San Francisco, due to its common practice, making three right turns is known colloquially as a "San Francisco left turn". Likewise, as many intersections in
Turning rules are by no means universal. For example, in New Zealand (a drive-on-the-left country) between 1977 and 2012, left turning traffic had to give way to opposing right-turning traffic wishing to take the same road (unless there were multiple lanes, but then one must take care in case a vehicle jumped lanes). New Zealand abolished this particular rule on 25 March 2012, except at roundabouts or when denoted by a Give Way or Stop sign.[8] Although the rule caused initial driver confusion, and many intersections required or still require modification,[9] the change is predicted to eventually prevent one death and 13 serious injuries annually.
On roads with multiple lanes, turning traffic is generally expected to move to the lane closest to the direction they wish to turn. For example, traffic intending to turn right will usually move to the rightmost lane before the intersection. Likewise, left-turning traffic will move to the leftmost lane. Exceptions to this rule may exist where for example the traffic authority decides that the two rightmost lanes will be for turning right, in which case drivers may take whichever of them to turn. Traffic may adapt to informal patterns that rise naturally rather than by force of authority. For example, it is common for drivers to observe (and trust) the turn signals used by other drivers in order to make turns from other lanes. If several vehicles on the right lane are all turning right, a vehicle may come from the next-to-right lane and turn right as well, in parallel with the other right-turning vehicles.
Intersections
In most of
In the United Kingdom, priority is generally indicated by signs or markings, so that almost all junctions between public roads (except those governed by traffic signals) have a concept of a major road and minor road. The default give-way-to-the-right rule used in Continental Europe causes problems for many British and Irish drivers who are accustomed to having right of way by default unless otherwise indicated. A very small proportion of low-traffic junctions are unmarked – typically on housing estates or in rural areas. Here the rule is to "proceed with great care"[10] i.e. slow the vehicle and check for traffic on the intersecting road.
Other countries use various methods similar to the above examples to establish the right of way at intersections. For example, in most of the United States, the default priority is to yield to traffic from the right, but this is usually overridden by traffic control devices or other rules, like the boulevard rule. This rule holds that traffic entering a major road from a smaller road or alley must yield to the traffic of the busier road, but signs are often still posted. The boulevard rule can be compared with the above concept of a major and minor road, or the priority roads that may be found in countries that are parties to the Vienna Convention on Road Signs and Signals.
Perpendicular intersections Also known as a "four-way" intersection, this intersection is the most common configuration for roads that cross each other, and the most basic type.
If
In the United States, South Africa, and Canada, there are four-way intersections with a stop sign at every entrance, called four-way stops. A failed signal or a flashing red light is equivalent to a four-way stop, or an all-way stop. Special rules for four-way stops may include:
- In the countries that use four-way stops, pedestrians always have priority at crosswalks – even at unmarked ones, which exist as the logical continuations of the sidewalks at every intersection with approximately right angles – unless signed or painted otherwise.
- Whichever vehicle first stops at the stop line – or before the crosswalk, if there is no stop line – has priority.
- If two vehicles stop at the same time, priority is given to the vehicle on the right.
- If several vehicles arrive at the same time, a right-of-way conflict may arise wherein no driver has the legal right-of-way. This may result in drivers informally signaling to other drivers to indicate their intent to yield, for example by waving or flashing headlights.[11]
In Europe and other places, there are similar intersections. These may be marked by special signs (according to the Vienna Convention on Road Signs and Signals), a danger sign with a black X representing a crossroads. This sign informs drivers that the intersection is uncontrolled and that default rules apply. In Europe and in many areas of North America the default rules that apply at uncontrolled four-way intersections are almost identical:
- Rules for pedestrians differ by country, in the United States and Canada pedestrians generally have priority at such an intersection.
- All vehicles must give priority to any traffic approaching from their right,
- Then, if the vehicle is turning right or continuing on the same road it may proceed.
- Vehicles turning left must also give priority to traffic approaching from the opposite direction, unless that traffic is also turning left.
- If the intersection is congested, vehicles must alternate directions and/or circulate priority to the right one vehicle at a time. [citation needed]
Protected intersection for bicycles
A number of features make this protected intersection. A corner refuge island, a setback crossing of the pedestrians and cyclists, generally between 1.5–7 metres of setback, a forward stop bar, which allows cyclists to stop for a traffic light well ahead of motor traffic who must stop behind the crosswalk. Separate signal staging or at least an advance green for cyclists and pedestrians is used to give cyclists and pedestrians no conflicts or a head start over traffic. The design makes a right turn on red, and sometimes left on red depending on the geometry of the intersection in question, possible in many cases, often without stopping.[12]
This type of intersection is common in the bicycle-friendly Netherlands.[13]
Pedestrian crossings
Pedestrians must often cross from one side of a road to the other, and in doing so may come into the way of vehicles traveling on the road. In many places pedestrians are entirely left to look after themselves, that is, they must observe the road and cross when they can see that no traffic will threaten them. Busier cities usually provide
The actual appearance of pedestrian crossings varies greatly, but the two most common appearances are: (1) a series of lateral white stripes or (2) two longitudinal white lines. The former is usually preferred, as it stands out more conspicuously against the dark pavement.
Some pedestrian crossings accompany a
Pedestrian crossings without traffic signals are also common. In this case, the traffic laws usually states that the pedestrian has the right of way when crossing, and that vehicles must stop when a pedestrian uses the crossing. Countries and driving cultures vary greatly as to the extent to which this is respected. In the state of Nevada the car has the right of way when the crosswalk signal specifically forbids pedestrian crossing. Traffic culture is a determinant factor for the behaviors of all road users’ traffic. Specifically, it has a main role in crashes.[14]
Some jurisdictions forbid crossing or using the road anywhere other than at crossings, termed jaywalking. In other areas, pedestrians may have the right to cross where they choose, and have right of way over vehicular traffic while crossing.
In most areas, an intersection is considered to have a crosswalk, even if not painted, as long as the roads meet at approximate right angles. The United Kingdom and Croatia are among the exceptions.
Pedestrian crossings may also be located away from intersections.
Level crossings
A level crossing is an at-grade intersection of a railway by a road. Because of safety issues, they are often equipped with closable gates, crossing bells and warning signs.
Speed limits
The higher the speed of a vehicle, the more difficult collision avoidance becomes and the greater the damage if a collision does occur. Therefore, many countries of the world limit the maximum speed allowed on their roads. Vehicles are not supposed to be driven at speeds which are higher than the posted maximum.
To enforce speed limits, two approaches are generally employed. In the United States, it is common for the police to patrol the streets and use special equipment (typically a radar unit) to measure the speed of vehicles, and pull over any vehicle found to be in violation of the speed limit. In Brazil, Colombia and some European countries, there are computerized speed-measuring devices spread throughout the city, which will automatically detect speeding drivers and take a photograph of the license plate (or number plate), which is later used for applying and mailing the ticket. Many jurisdictions in the U.S. use this technology as well.
A mechanism that was developed in Germany is the Grüne Welle, or green wave, which is an indicator that shows the optimal speed to travel for the synchronized green lights along that corridor. Driving faster or slower than the speed set by the behavior of the lights causes the driver to encounter many red lights. This discourages drivers from speeding or impeding the flow of traffic. See related traffic wave and Pedestrian Crossings, above.
Overtaking
Overtaking (or passing) refers to a maneuver by which one or more vehicles traveling in the same direction are passed by another vehicle. On two-lane roads, when there is a split line or a dashed line on the side of the overtaker, drivers may overtake when it is safe. On multi-lane roads in most jurisdictions, overtaking is permitted in the "slower" lanes, though many require a special circumstance. See "Lanes" below.
In the United Kingdom and Canada, notably on extra-urban roads, a solid white or yellow line closer to the driver is used to indicate that no overtaking is allowed in that lane. A double white or yellow line means that neither side may overtake.
In the United States, a solid white line means that lane changes are discouraged and a double white line means that the lane change is prohibited.
Lanes
When a street is wide enough to accommodate several vehicles traveling side-by-side, it is usual for traffic to organize itself into lanes, that is,
On roads that have multiple lanes going in the same direction, drivers may usually shift amongst lanes as they please, but they must do so in a way that does not cause inconvenience to other drivers. Driving cultures vary greatly on the issue of "lane ownership": in some countries, drivers traveling in a lane will be very protective of their right to travel in it while in others drivers will routinely expect other drivers to shift back and forth.
Designation and overtaking
The usual designation for lanes on
When driving on the left:
- The lane designated for faster traffic is on the right.
- The lane designated for slower traffic is on the left.
- Most freeway exits are on the left.
- Overtaking is permitted to the right, and sometimes to the left.
When driving on the right:
- The lane designated for faster traffic is on the left.
- The lane designated for slower traffic is on the right.
- Most freeway exits are on the right.
- Overtaking is permitted to the left, and sometimes to the right.
Countries party to the Vienna Convention on Road Traffic have uniform rules about overtaking and lane designation. The convention details (amongst other things) that "Every driver shall keep to the edge of the carriageway appropriate to the direction of traffic", and the "Drivers overtaking shall do so on the side opposite to that appropriate to the direction of traffic", notwithstanding the presence or absence of oncoming traffic. Allowed exceptions to these rules include turning or heavy traffic, traffic in lines, or situation in which signs or markings must dictate otherwise. These rules must be more strictly adhered to on roads with oncoming traffic, but still apply on multi-lane and divided highways. Many countries in Europe are party to the Vienna Conventions on traffic and roads. In Australia (which is not a contracting party), traveling in any lane other than the "slow" lane on a road with a speed limit at or above 80 km/h (50 mph) is an offence, unless signage is posted to the contrary or the driver is overtaking.
Many areas in North America do not have any laws about staying to the slowest lanes unless overtaking. In those areas, unlike many parts of Europe, traffic is allowed to overtake on any side, even in a slower lane. This practice is known as "passing on the right" in the United States and "overtaking on the inside" and "undertaking" in the United Kingdom. When referring to individual lanes on dual carriageways, one does not consider traffic travelling the opposite direction. The inside lane (in the British English sense, i.e. the lane beside the hard shoulder) refers to the lane used for normal travel, while the middle lane is used for overtaking cars on the inside lane. The outside lane (i.e. closest to oncoming traffic) is used for overtaking vehicles in the middle lane. The same principle lies with dual carriageways with more than three lanes.
U.S.-state-specific practices
In some US states (such as Louisiana, Massachusetts and New York), although there are laws requiring all traffic on a public way to use the right-most lane unless overtaking, this rule is often ignored and seldom enforced on multi-lane roadways. Some states, such as Colorado, use a combination of laws and signs restricting speeds or vehicles on certain lanes to emphasize overtaking only on the left lane, and to avoid a psychological condition commonly called road rage.
In California, cars may use any lane on multi-lane roadways. Drivers moving slower than the general flow of traffic are required to stay in the right-most lanes (by California Vehicle Code (CVC) 21654) to keep the way clear for faster vehicles and thus speed up traffic. However, faster drivers may legally pass in the slower lanes if conditions allow (by CVC 21754). But the CVC also requires trucks to stay in the right lane, or in the right two lanes if the roadway has four or more lanes going in their direction. The oldest freeways in California, and some freeway interchanges, often have ramps on the left, making signs like "TRUCKS OK ON LEFT LANE" or "TRUCKS MAY USE ALL LANES" necessary to override the default rule. Lane splitting, or riding motorcycles in the space between cars in traffic, is permitted as long as it is done in a safe and prudent manner.[15]
One-way roadways
In order to increase traffic capacity and safety, a route may have two or more separate roads for each direction of traffic. Alternatively, a given road might be declared one-way.
High-speed roads
In large cities, moving from one part of the city to another by means of ordinary streets and avenues can be time-consuming since traffic is often slowed by at-grade junctions, tight turns, narrow marked lanes and lack of a minimum speed limit. Therefore, it has become common practice for larger cities to build roads for faster through traffic. There are two different types of roads used to provide high-speed access across urban areas:
- The controlled-access highway (freeway or motorway) is a divided multi-lane highway with fully controlled access and grade-separated intersections (no cross traffic). Some freeways are called expressways, super-highways, or turnpikes, depending on local usage. Access to freeways is fully controlled; entering and leaving the freeway is permitted only at grade-separated interchanges.
- The limited-access road (often called expressway in areas where the name does not refer to a freeway or motorway) is a lower-grade type of road with some or many of the characteristics of a controlled-access highway: usually a broad multi-lane avenue, frequently divided, with some grade separation at intersections.
Minimum speed signs are sometimes posted (although increasingly rare) and usually indicate that any vehicle traveling slower than 40 mph (64 km/h) should indicate a slower speed of travel to other motor vehicles by engaging the vehicle's four-way flashing lights. Alternative slower-than-posted speeds may be in effect, based on the posted speed limit of the highway/freeway.
Systems of freeways and expressways are also built to connect distant and regional cities, notable systems include the
One-way streets
In more sophisticated systems such as large cities, this concept is further extended: some streets are marked as being one-way, and on those streets all traffic must flow in only one direction. Pedestrians on the sidewalks are generally not limited to one-way movement. Drivers wishing to reach a destination they have already passed must return via other streets. One-way streets, despite the inconveniences to some individual drivers, can greatly improve traffic flow since they usually allow traffic to move faster and tend to simplify intersections.
Congested traffic
In some places traffic volume is consistently, extremely large, either during periods of time referred to as rush hour or perpetually. Exceptionally, traffic upstream of a vehicular collision or an obstruction, such as
In measured traffic data,
Rush hour
During business days in most major cities,
Congestion mitigation
Rush hour policies
Some cities adopt policies to reduce rush-hour traffic and pollution and encourage the use of
In the United States and Canada, several expressways have a special lane (called an "HOV Lane" –
Metered freeways are also a solution for controlling rush hour traffic. In Phoenix, Arizona and Seattle, Washington, among other places, metered on-ramps have been implemented. During rush hour, traffic signals are used with green lights to allow one car per blink of the light to proceed on to the freeway.
Rush hour is typically caused by multiple cars all going to once place at the same time. There is no way to fix the issue because the economy has set times for work, school, and running errands all during the same hours. There is no avoiding this problem because it exists in every major metropolitan area in the world. [17]
Pre-emption
In some areas,
During emergencies where evacuation of a heavily populated area is required, local authorities may institute
Intelligent transportation systems
An intelligent transportation system (ITS) is a system of hardware, software, and operators-in-the-loop that allow better monitoring and control of traffic in order to optimize traffic flow. As the number of vehicle lane miles traveled per year continues to increase dramatically, and as the number of vehicle lane miles constructed per year has not been keeping pace, this has led to ever-increasing traffic congestion. As a cost-effective solution toward optimizing traffic, ITS presents a number of technologies to reduce congestion by monitoring traffic flows through the use of sensors and live cameras or analysing cellular phone data travelling in cars (floating car data) and in turn rerouting traffic as needed through the use of variable message boards (VMS), highway advisory radio, on board or off board navigation devices and other systems through integration of traffic data with navigation systems. Additionally, the roadway network has been increasingly fitted with additional communications and control infrastructure to allow traffic operations personnel to monitor weather conditions, for dispatching maintenance crews to perform snow or ice removal, as well as intelligent systems such as automated bridge de-icing systems which help to prevent accidents.
See also
- Air traffic control
- Rules of the road in Australia
- Bicycle safety
- Braess's paradox
- Cross-sea traffic ways
- Induced demand
- Institute of Transportation Engineers
- International Regulations for Preventing Collisions at Sea
- Journal of Transport and Land Use
- Last clear chance
- Line source
- Multistorey car park
- Rules of the road in New Zealand
- Road traffic control device
- Road traffic safety
- Road transport
- Rules of the road in China
- Three-phase traffic theory
- Traffic light
- Traffic psychology
- Traffic law
- Trafficability
- Transportation forecasting
References
- ^ "Traffic definition and meaning | Collins English Dictionary". www.collinsdictionary.com. Retrieved 3 January 2020.
- ^ "traffic". American Heritage Dictionary (Fifth ed.). 2013. Retrieved 23 March 2014.
- ^ a b c Harper, Douglas (2001–2014). "traffic (n.)". Online Etymological Dictionary. Retrieved 23 March 2014.
- ^ a b "traffic, n.". OED Online. Oxford University Press. March 2014.
- ^ Davies v. Mann, 152 Eng. Rep. 588 (1842)
- ^ see legal doctrine of Last Clear Chance
- ^ a b "14 CFR 91.113". Code of Federal Regulations. 27 July 2004. Retrieved 24 November 2023.
- ^ Dearnaley, Mathew (2 September 2011). "Give-way rule change: Campaign to avoid crashes". The New Zealand Herald. Retrieved 23 November 2011.
- ^ Preston, Nikki (23 February 2012). "'Wait and see approach' on left turn rule". The New Zealand Herald. Retrieved 26 February 2012.
- ^ "The Highway Code – Rule 176". Retrieved 7 November 2012.
- ^ Oosting, Jonathan (3 September 2012). "Traffic Talk: Breaking down four-way stop sign scenarios, laws and common-sense courtesies". mlive. Archived from the original on 17 September 2017.
- ^ "Out of the Box Transcript.docx" (PDF). Archived (PDF) from the original on 9 October 2022. Retrieved 20 September 2018.
- ^ "Junction design in the Netherlands". 23 February 2014.
- S2CID 26702114.
- ^ WhyBike? (6 March 2006). "All the info you need on lanesharing (lanesplitting)".
- ^ Andrew Downie (21 April 2008). "The World's Worst Traffic Jams". Time. Retrieved 2008-06-20
- ^ Downs, Anthony (1 January 2004). "Traffic: Why It's Getting Worse, What Government Can Do". Brookings. Retrieved 2 June 2023.
- ^ "625 ILCS 5/12-601.1. Traffic control signal preemption devices.". Illinois Compiled Statutes. Illinois General Assembly. 2 July 2003. Retrieved 2 December 2018.
Further reading
- May, Adolf. Traffic Flow Fundamentals. Prentice Hall, Englewood Cliffs, NJ, 1990.
- 2010 Highway Capacity Manual. Transportation Research Board, Washington, D.C. ISBN 0-309-06681-6,
- Taylor, Nicholas. The Contram dynamic traffic assignment model TRL 2003
- B. S. Kerner, The Physics of Traffic, Springer, Berlin, New York, 2004
- B. S. Kerner, Introduction to Modern Traffic Flow Theory and Control: The Long Road to Three-Phase Traffic Theory, Springer, Berlin, New York, 2009
- Traffic Monitoring: A Guidebook Federal Highway Administration
- Vanderbilt, Tom. Traffic: Why We Drive the Way We Do (and What It Says About Us). Knopf, New York, 2008.