A raised pavement marker is a safety device used on roads. These devices are usually made with plastic, ceramic, thermoplastic paint, glass or occasionally metal, and come in a variety of shapes and colors. Raised reflective markers, such as plastic, ceramic, or metal ones, include a lens or sheeting that enhances their visibility by retroreflecting automotive headlights, while glass road studs gather automotive headlights with a dome shape and reflect the lights with a reflective layer within. Some other names for specific types of raised pavement markers include convex vibration lines, Botts' dots, delineators, cat's eyes, road studs, or road turtles. Sometimes they are simply referred to as "reflectors".
Convex vibration marking line The surface of this type of vibrating coating line is distributed and scattered with raised bumps. Some bumps are coated with high-refractive-index glass beads. When a speeding vehicle runs over the raised road lines, it produces a strong warning vibration to remind the car driver of deviation from the lane. Perpendicular to driving directions, these marking lines are used for settled mainline toll plaza, ramp entrances, mountainous areas, continuous sharp turns, downhill sections and the end of the highway (intersection of highway exit and the plane of the common roadway), gates and entrances of enterprises, institutions, and school. In the same direction of traffic driving direction, they are mainly settled in the median strip, edge lines, and dangerous sections of the road.
Reflective raised pavement markers
In the United States, Canada, Mexico, some countries of South America, Thailand and Australia, these plastic devices commonly have two angled edges facing drivers and contain one or more corner reflector strips. The marker is generally held in place using butyl pads, epoxy glue, or bitumen. In areas with little snowfall, reflective raised pavement markers are applied directly on top of the road surface. The device's retroreflective surface enables the device to be clearly visible at long distances at night and in rainy weather. The devices come in multiple colors in accord with local traffic marking standards. In 1965 San Diego Police Motorcycle Officer Kenneth Grant Maine, improved upon and applied for a patent on the white epoxy-resin reflective raised pavement marker. He then submitted it to the California Bureau of Highways, later called the California Department of Transportation, which is now known as Caltrans. In areas where snowplowing is frequent, conventional markers are placed in a shallow groove cut in the pavement, or specially designed markers are used which include a protective metal casting that is embedded in recesses in the pavement, allowing the marker to protrude slightly above the pavement surface for increased visibility, much like a cat's eye.
Lit LED in-pavement Raised Pavement Markings (RPMs), help improve road safety, as they are more generally visible than reflective RPM markings as they are internally lit and don't require headlights to show up. The RPMs are usually raised for visibility, but in snowplow areas these types of RPMs can be installed flush-mounted within the pavement to avoid the snowplows. There are a number of types, ranging from a single LED point source RPMs, with limited daytime visibilities, (road studs), to multi-LED linear type RPMs, visible in all full sunlight and nighttime applications. Some lit RPMs can be visible and useful in both bright sunlight as well as nighttime applications, whilst others are only visible at nighttime or in low light applications. One of the key differences between these types is that lit linear RPMs, being linear, each lit unit provides both positional and directional guidance to viewers. For single-point source viewer directional guidance, a number of these units must all be viewed at the same time. In severe weather, such as fog or snow whiteouts, this may not be possible. Therefore, as each linear visual aid provides both positional and directional guidance, this type is more helpful as in a wider variety of weather conditions and light conditions. Some lit linear visual aids / RPMs, melt snow, without needing any additional heating elements, as such, these types or self-cleaning RPMs are more energy-efficient compared to those that need additional heating elements to melt snow so are NOT self-cleaning. Linear visual aids can also be used for creating in-pavement signs and messages such as lit merge arrows. Point source RPMs could be used for such signage. However, because they are installed close together, and deep within the pavement compared to linear RPMs, such usage would tend to damage the road, especially in the case of asphalt roads.
Usage of color
In Europe
In almost all European countries, such markers will include reflective lenses of some kind. Most appear white or gray during daylight; the colors discussed here are the color of light they reflect. Because of their inconspicuousness during the day, they are always used in conjunction with painted retro-reflective lines; they are never seen on their own.
White markers — for lane markings. When used on dual carriageways, motorways or one-way roads, they may illuminate red on the reverse, to indicate drivers are traveling the wrong way. Yellow or amber markers — These are found next to the central reservation (US: median) on motorways and dual carriageways and, in the Republic of Ireland, are also used on hard shoulders. Red markers — These are found by the hard shoulder on motorways and at the edge of the running surface on other roads. They are also occasionally used to indicate a no-entry road and when travelling down the wrong way of the motorway/dual carriageway. Green markers — These are used where slip-roads (US: off-ramp) leave and join the main carriageway on dual carriageways. In some countries, they are also used across the entrances of minor roads or accesses onto major single carriageway roads or lay-bys. Blue markers — Are used to indicate the entrance to police reserved slip-roads (these do not lead anywhere, they are to allow police to park and monitor motorway traffic). The exception to the above rules are:
… excerpt ends here. Continue reading the full article.
