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traffic light controler


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traffic light controler

  1. 1. Review on the topic traffic light Kaushal kumar gupta* *,* UG Stdents, Dr.M.G.R UniversityAbstract IntroductionA common mechanism that allows control of Traffic lights, which may also be knownvehicular flow in big cities is the use of traffic as stoplights, traffic lamps, traffic signals, signallights. Generally, each traffic light on an lights, robots or semaphores, are signallingintersection is assigned a constant green time. devices positioned at roadIn last years several agent-based traffic simu intersections, pedestrian crossings and otherlators have been proposed to show how better locations to control competing flows of traffic.results can be achieved with respect to traffic Traffic lights were first installed in 1868flow variables, like vehi cles’ route time and in London, United Kingdom, and are today used invehicles’ waiting time. It is possible to propose almost every city of the world. Traffic lightsagent-based coordination schemes where the alternate the right of way accorded to road usersgreen time of the traffic lights is assigned based by displaying lights of a standard color (red,on the present conditions of traffic. Due to yellow/amber, and green) following athose intelligent assignations on the traffic universal color code (and a precise sequence tolights’ green time, it’s reasonable to think that enable comprehension by those who are colorvehicles’ waiting time could be reduced. In this blind).paper we compare two traffic light coordination mechanisms of an intersection that assign Typestraffic lights’ green time based on approximate Single aspectsinformation about traffic conditions. It is The simplest traffic light comprises either acompared the vehicles’ waiting time on the single or a pair of colored aspects that warnstraditional mechanism with respect to an any user of the shared right of way of a possibleauction mech anism, in which the traffic lights conflict or danger.Flashing Red: Treat as a stopare “selfish”, and to a negotiation mechanism sign. Also can signal the road is closed.where the traffic lights work with a “non-selfish” approach in the intersection. Our Flashing Yellow: Caution, crossing or roadresults show that the negotiation mechanism, hazard ahead Flashing Green: Varies amongunder certain con ditions, gets better results jurisdiction; can give permission to go straightover the traditional and auction mechanisms. as well as make a left turn in front of opposing traffic (which is held by a steady red light), or
  2. 2. can indicate the end of a green cycle before the red (beep ..... beep ..... beep) and a continuouslight changes to a solid yellow. buzzing sound when the lights are green. In New South Wales, Victoria and WesternDual aspects Australia the sound is produced in the sameThese are often seen at railway crossings and at unit as the push buttons. This systemintersections of streets and emergency of assistive technology is also widely used atdepartment driveways. They will flash yellow busy intersections in Canadian cities.when cross traffic is not expected, and turn redto stop traffic when cross traffic occurs. The United Kingdom, the Puffin crossings and their predecessor, the Pelican crossing, willThree or more aspects make a slow beeping sound to indicate that it isThe standard is the red light above the green, safe to cross the road. The beeping sound iswith yellow between. When sideways, the disabled during the night time so as not toarrangement depends on the rule of the road. disturb any nearby residents.In right-lane countries, the green light is on theright, and in left-lane countries, the left. Light for Public transportOther signals are sometimes added for more Traffic lights for public transport often usecontrol, such as for public transportation and signals that are distinct from those for privatepermissive turns. For a brief time, they also turn traffic. They can be letters, arrows or bars ofred in all directions, to clear any traffic in the white or colored light.intersection. The delay can depend on traffic,road conditions, and the kind of intersection. In Portland, Oregon, the tram signals feature an orange horizontal bar and a white vertical bar.The three-aspect standard is also used at locks Some systems use the letter B for buses, and Ton the Upper Mississippi River. Red means that for trams.another vessel is passing through. Yellow meansthat the lock chamber is being emptied or filled In Russia, dedicated traffic signals for publicto match the level of the approaching vessel. transport (tram, trolleybus or bus) have fourAfter the gate opens, green means that the white lights that form the letter T. If the threevessel may enter. top lamps are lit, this means "stop". If the bottom lamp and some lamps on the top rowIn Quebec, lights are often sideways, but each a are lit, this means permission to go in adifferent shape: red is a square (larger than the direction shown. In case of a tram signal, ifnormal circle), yellow is a diamond, and green is there are no tram junctions on an intersection,a circle. a simpler system of one yellow signal in the form of letter T is used instead; the tram mustSounds proceed only when the signal is lit.In some jurisdictions such as Australia, In North European countries the tram signalspedestrian lights are associated with a sound feature white lights of different forms: "S" fordevice, for the benefit of blind and visually "stop", "—" for "caution" and arrows to permitimpaired pedestrians. These make a slow passage in a given direction.beeping sound when the pedestrian lights are
  3. 3. been passed by the vehicle that triggered the preemption. In lieu of pre-emptive mechanisms, in most jurisdictions, emergency vehicles are not required to respect traffic lights, but must activate their own emergency lights when crossing an intersection against the light, in order to alert oncoming drivers to the preemption.Preemption Turning signals and rulesSome regions have signals that areinterruptible, giving priority to special traffic.Such traffic light preemption is usually reservedforemergency vehicles such as fireapparatus, ambulances, and police squad cars,though sometimes mass transit vehiclesincludingbuses and light rail trains can interruptlights. Most of the systems operate with smalltransmitters that send radiowaves, infraredsignals, or strobe light signals thatare received by a sensor on or near the trafficlights. Some systems use audio detection,where a certain type of siren must be used anddetected by a receiver on the traffic lightstructure.Upon activation the normal traffic light cycle issuspended and replaced by the "preemptionsequence": the traffic lights to all approaches tothe intersection are switched to "red" with theexception of the light for the vehicle that hastriggered the preemption sequence. .Sometimes, an additional signal light is placed In some instances, traffic may turn left (in left-nearby to indicate to the preempting vehicle driving jurisdictions) or right (in right-drivingthat the preempting sequence has been jurisdictions) after stopping at a red light,activated and to warn other motorists of the providing they give way to the pedestrians andapproach of an emergency vehicle. The normal other vehicles. In some places that generallytraffic light cycle resumes after the sensor has disallow this, a sign next to the traffic light indicates that it is allowed at a particular
  4. 4. intersection. Conversely, jurisdictions that left turn signals, a left-pointing arrow turnsgenerally allow this might forbid it at a green when traffic may turn left withoutparticular intersection with a "no turn on red" opposing traffic and pedestrian conflict, andsign, or put a green arrow to indicate turns red or disappears otherwise. Such a signalspecifically when a turn is allowed without is referred to as a "protected" signal if it has itshaving to yield to pedestrians (this is usually own red phase; a "permissive" signal does notwhen traffic from the perpendicular street is have such a feature. Three standard versions ofmaking a turn onto ones street and thus no the permissive signal exist: One version is apedestrians are allowed in the intersection horizontal bar with five lights - the green andanyway). Some jurisdictions allow turning on yellow arrows are located between thered in the opposite direction (left in right- standard green and yellow lights. A vertical 5-driving countries; right in left-driving countries) light bar holds the arrows underneath thefrom a one-way road onto another one-way standard green light (in this arrangement, theroad; some of these even allow these turns yellow arrow is sometimes omitted, leaving onlyfrom a two-way road onto a one-way the green arrow below the solid green light, orroad.[22] Also differing is whether a red arrow possibly an LED based device capable ofprohibits turns; some jurisdictions require a "no showing both green and yellow arrows within aturn on red" sign in these cases. A study in single lamp housing). Some newer LED turnthe State of Illinois (a right-driving jurisdiction) arrows seen in parts of Canada are capable ofconcluded that allowing drivers to proceed multicolored animation. Such lights will oftenstraight on red after stopping, at specially display a flashing and animated green or yellowposted T-intersections where the intersecting arrow when the dedicated turn is allowed, butroad went left only, was dangerous.[citation then transform into a red arrow on a whiteneeded] Proceeding straight on red at T- background with a red line through it,intersections where the intersecting road went emphasising that the turn is no longer allowed.left only used to be legal in Mainland China, These lights will also often have the words "NOwith right-hand traffic provided that such TURN" displayed, or an explanatory reason whymovement would not interfere with other the turn is not allowed, such as "TRAIN" in thetraffic, but when the Road Traffic Safety Law of case of a rail or light rail crossing. A third type isthe Peoples Republic of China took effect on 1 known as a "doghouse" or "cluster head" - aMay 2004, such movement was outlawed.[23] In vertical column with the two normal lights is onsome other countries, the permission is the right side of the signal, a vertical columnindicated by a flashing yellow arrow (cars do with the two arrows is located on the left, andnot have to stop but must give way to other the normal red signal is in the middle above thecars and pedestrians). two columns. Cluster signals in Australia and New Zealand use six signals, theAnother distinction is between intersections sixth being a red arrow that can operatethat have dedicated signals for turning across separately from the standard red light. In athe flow of opposing traffic and those that do fourth type, sometimes seen at intersectionsnot. Such signals are called dedicated left-turn in Ontario and Quebec, Canada, there is nolights in the United States and Canada (since dedicated left-turn lamp per se. Instead, theopposing traffic is on the left). With dedicated normal green lamp flashes rapidly, indicating
  5. 5. permission to go straight as well as make a left opposing traffic to clear, attempting to make anturn in front of opposing traffic, which is being illegal left turn on red. A dedicated left-turnheld by a steady red lamp. (This "advance signal that appears at the end of the greengreen," or flashing green can be somewhat phase is called a lagging turn. If there is no left-startling and confusing to drivers not familiar turn signal, the law requires one to yield towith this system. This also can cause confusion oncoming traffic and turn when the intersectionamongst visitors to British Columbia, where a is clear and it is safe to do so. Nevertheless, it isflashing green signal denotes a pedestrian increasingly and disturbingly common in at leastcontrolled crosswalk. Another interesting the U.S. to see drivers who do not yield in thepractice seen at least in Ontario is that cars absence of a dedicated signal, cutting off trafficwishing to turn left that arrived after the left that has right-of-way and is starting to headturn signal ended can do so during the yellow across the intersection. In the U.S., many olderphase, as long as there is enough time to make inner-city and rural areas do not have dedicateda safe turn. left-turn lights, while most newer suburban areas have them. Such lights tend to decreaseA flashing yellow arrow, which allows drivers to the overall efficiency of the intersection as itmake left turns after giving way to oncoming becomes congested, although it makestraffic, is becoming more widespread in the intersections safer by reducing the risk of head-United States, particularly in Oregon. In the on collisions and may even speed up throughnormal sequence, a protected green left-turn traffic, but if a significant amount of traffic isarrow will first change to a solid yellow arrow to turning, a dedicated turn signal helps eliminateindicate the end of the protected phase, then to congestion.a flashing yellow arrow, which remains flashinguntil the standard green light changes to yellow Conclusionand red. These generally take the form of foursignal sections (green, yellow, yellow arrow, The improvement of town traffic condition isred). On some newer signals, notably in the city largely dependent on the modern ways ofof Bend, the green and flashing yellow arrows traffic management and control. Advancedemanate from the same light section through traffic signal controllers and control systemthe use of a dual-color LED array, while the solid contribute to the improvement of the urbanyellow arrow is mounted above it. traffic problem. The intelligent of traffic signal controller that is introduced in this project withGenerally, a dedicated left-turn signal is powerful functions and hardware interface.illuminated at the beginning of the green phase Good quality social benefit has been madeof the green-yellow-red-green cycle. This is through the application of the intelligent trafficcalled a leading turn. This allows left-turn controller in practice, and the application resulttraffic, which often consists of just a few cars, to shows that the intelligent traffic signalvacate the intersection quickly before giving controller will improve.priority to vehicles traveling straight. Thisincreases the throughput of left-turn trafficwhile reducing the number of drivers, perhapsfrustrated by long waits in heavy traffic for