Normal traffic light functions require more than a few controls and coordination to ensure that traffic and pedestrians move smoothly, and as safely as possible. Different control systems are used to achieve this, from simple clockwork mechanisms to sophisticated computerized control systems and advanced coordination to minimize the delays of people using the road.
Video Traffic light control and coordination
Fase dan tahapan
Traffic control uses the phase concept, which is the direction of movement grouped together. For example, a simple T-junction may have three phases of vehicle movement, one for each intersection arm. There may be additional phases for other movements such as pedestrians, cyclists, bus lanes or trams.
A stage is a non-conflict phase group that is moving at the same time.
Maps Traffic light control and coordination
Traffic control system
Traffic signals are usually controlled by controllers installed in the cabinet. Some electro-mechanical controllers are still in use (New York City still has 4,800 in 1998, although the numbers are now lower due to the prevalence of signal control boxes). However, modern traffic controllers are solid state. The cabinet usually contains a power panel, to distribute electrical power in the cabinet; panel interface detector, to connect to the detector loop and other detectors; amplifier detector; controller itself; conflict monitor units; transfer of flash relay; police panels, to allow police to deactivate signals; and other components.
In the United States, controllers are standardized by NEMA, which sets standards for connectors, operating limits, and intervals. The TS-1 standard was introduced in 1976 for the first generation of solid-state controllers.
Solid state controllers are required to have independent conflict monitoring units (CMUs), ensuring safe-failing operation. CMU monitors the output of the controller, and if an error is detected, CMU uses a flash transfer relay to place the intersection into FLASH , with all the red lights blinking, rather than displaying potentially dangerous combinations. signal. CMU is programmed with a combination of allowable lights, and will detect if the controller provides landing conflicting green signals, for example.
In the late 1990s, a national standardization effort known as Advanced Transport Controller (ATC) was conducted in the United States by the Institute of Transportation Engineers. The project is trying to create a national standard for traffic light controllers. The standardization effort is part of the National Intelligence Transportation system program funded by various road bills, starting with the ISTEA in 1991, followed by TEA-21, and subsequent bills. The controller will communicate using the National Transport Communication for ITS Protocol (NTCIP), based on the Internet Protocol, ISO/OSI, and ASN.1.
Traffic lights should be instructed when to change the stage and are usually coordinated so that the stage changes occur in some connection with other nearby signals or press the pedestrian button or to a timer action or some other input.
Battery backup
In areas susceptible to power failures, the addition of a battery backup to a traffic control system can improve the safety of motorists and pedestrians. In the past, a larger capacity of uninterruptible power supplies is required to continue full operation of traffic signals using incandescent bulbs. The cost for such a system would be a barrier. After a new generation of traffic signals using LED lights that consume 85-90% less energy, it is now possible to insert a battery backup into the traffic light system. The battery backup will be installed in the traffic control cabinet or in its own cabinet adjacent to the controller.
The battery backup can operate the controller in an emergency mode with a flashing red light or in full function mode. In 2004, the California Energy Commission recommended that local governments turn traffic lights into LEDs with backup batteries. This will lower energy consumption and improve security at key intersections. Recommendations are for systems that provide fully functional traffic signals for two hours after a power outage. Then the signal will have a flashing red light for two hours.
Fixed time control
In traffic control, a simple and old form of signal controller is known as an electro-mechanical signal controller. Unlike computerized signal controllers, electro-mechanical signal controllers consist mostly of movable parts (cams, dial, and shafts) that control signals connected to them correctly. Apart from the movable parts, electric relays are also used. In general, the electro-mechanical signal controller uses a fixed dial timer, indicating the intersection time plan. The length of the junction marked junction is determined by a small gear located inside the dial timer. The gears, as they are commonly known, range from 35 seconds to 120 seconds. If the gear in the dial timer generates failure, it can be replaced with other cycle fixtures that would be appropriate to use. Since the dial timer has only one plan of signaled junction time, it can control the phase at a marked intersection in only one way. Many old signaled intersections still use electro-mechanical signal controllers, and the signals controlled by them are effective in one grid way where it is often possible to coordinate signals to the posted speed limits. However, they are unfavorable when the signal time of an intersection will benefit from adaptation to the dominant flow that changes over time.
Coordinated control
Efforts are often made to place traffic signals on a coordinated system so that drivers face green waves, long strings of green light (technical terms are developments). The difference between a coordinated signal and a synchronized signal is very important. The synchronized signals all change at the same time and are only used in special instances or in older systems. The coordinated (growing) system is controlled from the main controller and is set up for successive "cascade" lamps so that the vehicle's platoon can proceed through a series of sustainable green lights. The graphical representation of the phase state on the two-axis distance versus time plane clearly indicates the "green band" that has been established based on the distance of the signaled intersection and expected vehicle speed. In some countries (eg Germany, France, and the Netherlands), this "green ribbon" system is used to limit speed in certain areas. The lights are bordered in such a way that the rider can go without stopping if the speed is lower than the given limit, mostly 50 km/h (30 mph) in urban areas. This system is known as "grÃÆ'¼ne Welle" in German, "vague verte" in French, or "golf groene" in Dutch (English: "green wave"). Such systems are commonly used in urban areas of the United States from the 1940s, but are less common today. In England, Slough in Berkshire part of the A4 experimented with this. Many US cities set green waves on two-way streets to operate in more traversed directions, rather than trying to increase traffic in both directions. But the recent introduction of blinking yellow arrows (see Operation and traffic light signaling) creates a lead-lag signal, development assistance, available with permissive curves.
In modern coordinated signal systems, it is possible for drivers to travel long distances without facing red lights. This coordination is done easily only on one-way streets with fairly constant traffic levels. Two-way streets are often set to fit the rush hour to accelerate the heavier volume direction. Congestion can often damage coordination. On the other hand, some traffic signals are coordinated to prevent drivers from facing long lines of green light. This practice reduces high traffic volumes by encouraging delays but prevents congestion. Speed ​​is self-regulated in a coordinated signal system; drivers traveling too fast will arrive at red indications and end up stopping, drivers traveling too slow will not arrive at the next signal in time to take advantage of green indications. But in synchronized systems, drivers often use excessive speed to get through as many lights as possible.
Recently even more sophisticated methods have been used. Traffic lights are sometimes controlled centrally by monitors or by computers to allow them to be coordinated in real time to handle changing traffic patterns. Video cameras, or sensors grown on the sidewalks can be used to monitor traffic patterns across cities. Uncoordinated sensors occasionally block traffic by detecting pauses and flushing when the car arrives from the previous light. The most advanced systems use dozens of sensors and cost hundreds of thousands of dollars per intersection, but can greatly control traffic levels. This reduces the need for other actions (such as new roads) that are even more expensive.
Benefits include:
- Increase road traffic handling capacity
- Reduce collisions and wait times for vehicles and pedestrians
- Drive travel within speed limits to meet the green light
- Reduce unnecessary stop and start of traffic - this in turn reduces fuel consumption, air pollution and noise, as well as wear and tear of vehicles
- Reduce travel time
- Reduce driver disappointment and street outrage
Source of the article : Wikipedia
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