Legal implications for traffic lights

In virtually all jurisdictions in which they are used, it is an offence for motorists (and other road users) to disregard the instructions of traffic lights (or other traffic control devices). Exceptionally, it is not an offence for pedestrians to cross against a red light in the United Kingdom, where pedestrian lights officially give advice, rather than an instruction, although UK pedestrians do commit an offence if they cross a road against the signals of a police officer controlling traffic. Continue reading “Legal implications for traffic lights”

Traffic signal warrants

Traffic signals have strengths and weaknesses that must be considered when deciding whether to install them. Signaled intersections can reduce delay for side road traffic and reduce the occurrence of collisions by turning traffic and cross traffic. But they may also cause delay for traffic on the main road, and often increase rear-end collisions by up to 50%. Since right-angled and turn-against-traffic collisions are more likely to result in injuries, this is often an acceptable tradeoff. Continue reading “Traffic signal warrants”

Small vehicle safety of Traffic lights

In some instances the stoplight traffic detector will not change the light for small vehicles such as motorcycles and scooters. This is the result of the inability of the sensors to detect the presence of the small vehicle. A vehicle with sufficient mass consisting of a metal such as steel interacts with the sensors magnetic field causing the light to change at the appropriate time. Continue reading “Small vehicle safety of Traffic lights”

Traffic lights Implementation

According to transportation engineers, traffic lights can have both positive and negative effects on traffic safety and traffic flow. The separation of conflicting streams of traffic in time can reduce the chances of right-angle collisions. But also the frequency of rear-end crashes can be increased by the installation of traffic lights, and they can adversely affect the safety of bicycle and pedestrian traffic. Continue reading “Traffic lights Implementation”

Mounting of Traffic lights

There are significant differences from place to place in how traffic lights are mounted or positioned so that they are visible to drivers. Depending upon the location, traffic lights may be mounted on poles situated on street corners, hung from horizontal poles or wires strung over the roadway, or installed within large horizontal gantries that extend out from the corner and over the right-of-way. In the last case, such poles or gantries often have a lit sign with the name of the cross-street. Continue reading “Mounting of Traffic lights”

Traffic Light design

In the United States, traffic lights are currently designed with lights approximately 12 inches (300 mm) in diameter. Previously the standard had been 8 inches (200 mm), however those are slowly being phased out in favor of the larger and more visible 12 inch lights. Variations used have also included a hybrid design, which had one or more 12 inch lights along with one or more lights of 8 inches (200 mm) on the same light. Continue reading “Traffic Light design”

Conventional lighting systems of Traffic lights

Conventional traffic signal lighting, still common in some areas, utilizes a standard light bulb. Typically, a 67 watt, 69 watt, or 115 watt medium-base (household lamp in the U.S) light bulb provides the illumination. Light then bounces off a mirrored glass or polished aluminium reflector bowl, and out through a polycarbonate plastic or glass signal lens. Continue reading “Conventional lighting systems of Traffic lights”

Programmable Visibility Signals of Traffic Lights

Signals such as the 3M High Visibility Signal and McCain Programmable Visibility signal, utilize light diffusing optics and a powerful fresnel lens to create the signal indication. Lit via a powerful 150W PAR46 sealed-beam lamp, the light from the lamp in these “programmable visibility” signals passes through a set of two glass lenses at the back of the signal. The first lens, a frosted glass diffusing lens, diffuses the light into a uniform ball of light around five inches in diameter. The light then passes through a nearly identical lens known as an optical limiter (3M’s definition of the lens itself), also known as a “programming lens”, also five inches in diameter. Continue reading “Programmable Visibility Signals of Traffic Lights”

Optics and lighting of Traffic Lights

In the mid 1990s, cost-effective traffic light lamps using light-emitting diodes (LEDs) were developed; prior to this date traffic lights were designed using incandescent or halogen light bulbs. Unlike the incandescent-based lamps, which use a single large bulb, the LED-based lamps consist of an array of LED elements, arranged in various patterns. When viewed from a distance, the array appears as a continuous light source. Continue reading “Optics and lighting of Traffic Lights”

The History of Traffic light.

On 10 December 1868, the first traffic lights were installed outside the British Houses of Parliament in London, by the railway engineer J. P. Knight. They resembled railway signals of the time, with semaphore arms and red and green gas lamps for night use. The gas lantern was turned with a lever at its base so that the appropriate light faced traffic. Unfortunately, it exploded on 2 January 1869, injuring or killing the policeman who was operating it. Continue reading “The History of Traffic light.”

What is Traffic lights?

Traffic lights, which may also be known as stop lights, stoplight, traffic lamps, stop-and-go lights, robots or semaphore, are signaling devices positioned at road intersections, pedestrian crossings and other locations to control competing flows of traffic. Traffic lights have been installed in most cities around the world. They assign the right of way to road users by the use of lights in standard colors (Red – Amber – Green), using a universal color code (and a precise sequence, for those who are color blind). Continue reading “What is Traffic lights?”