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.
Japan, South Korea, Taiwan, Thailand and Croatia, along with some jurisdictions in the U.S. (including all in the State of New Mexico),some places in Canada and Mexico mount lights with their multiple faces arranged horizontally, often with supplemental vertical signals on the side, while others use vertical signals almost exclusively. Horizontal signals have consistent orientation, like their vertical counterparts.[19] Often, supplemental curb pedestal mounts, intended to support a signal for a different approach road, are used when primary signals are partially obscured due to structures such as overpasses, approaches around a building that obscures the primary signal mountings, and unusual approach geometry. In Florida, horizontal signals mounted on poles, known as “mast arms”, are in wide use due to their lower wind profile, important for minimising hurricane damage. The horizontally traffic light position is very common in Houston on most intersections.[citation needed]
California is particularly rigorous in ensuring that drivers can see the current state of a traffic light. One entrance to a typical large intersection, with three through lanes, two dedicated left-turn lanes, and a crosswalk, may have as many as three traffic lights for the left-turn lanes, three for the through lanes, and a pedestrian signal for the crosswalk. Those numbers must be multiplied by four to cover all four ways to enter a typical intersection.
In addition to being positioned and mounted for desired visibility for their respective traffic, some traffic lights are also aimed, louvered, or shaded to minimize mis-interpretation from other lanes. For example, a Fresnel lens on an adjacent through-lane signal may be aimed to prevent left-turning traffic from anticipating its own green arrow. One example of the Fresnel lens application common in the USA is the 3M Model 131 traffic signal (dubbed the “Programmed Visibility” signal). Although 3M has recently discontinued the M-131, it became a popular traffic signal for skewed or complex intersections. Today, McCain Traffic Systems (a traffic signal manufacturing company based in Vista, California) is the only U.S.-based manufacturer producing true “programmable visibility” traffic signals. In addition to aiming, Fresnel lenses, and louvers, visors and back panels are also useful in areas where sunlight would diminish the contrast and visibility of a signal face.
Traffic signals in most areas of Europe are located at the stop line on same side of the intersection as the approaching traffic (there being both right- and left-hand traffic) and are often mounted overhead as well as on side of the road. At particularly busy junctions for freight, higher lights may be mounted specifically for trucks. The stop line alignment is done to prevent vehicles blocking any crosswalk blocking and allow for better pedestrian traffic flow. There may also be a special area a few metres in advance of the stop line where cyclists may legally wait but not motor vehicles; this advanced stop line is often painted with a different road surface with greater friction and a high color, both for the benefit of cyclists and for other vehicles. The traffic lights are mounted so that cyclists can still see them.
In North America, there is often a pole-mounted signal on the same side of the intersection, but additional pole-mounted and overhead signals are usually mounted on the far side of the intersection for better visibility. In some areas, signals facing all four directions are hung directly over the intersection on a wire strung diagonally over the intersection.
In Lloydminster, a city straddling the provincial border between Alberta and Saskatchewan, an unusual jurisdictional arrangement can be found: motorists proceeding east at the intersection situated on the border must, while in Alberta, stop for a red signal located in Saskatchewan; the reverse applies for westbound motorists. If such a motorist were to disregard the signal and collide with a vehicle proceeding from that motorist’s left, the collision would occur in a province other than the one where the traffic control device is located.