The invention is concerned generally with roadway delineating apparatus, and more particularly with an improved raised-type marker particularly for separating traffic lanes, and capable of being struck by a snowplow blade without damage to the marker or the blade.
In areas which receive little or no snowfall, it is common for highways and other roadways to include series of "bumps" on the surface of the roadway, particularly between lanes. These raised markers, usually white or yellow, are highly visible in daytime and somewhat visible at night. They often comprise shallow ceramic domes, approximately four inches in diameter and flat-bottomed, adhered to the pavement surface by special epoxy cements. The use of the markers often eliminates the need for painting and repainting lane divider stripes on the roadway surface. However, to enhance the visibility of the dividing line in the daytime and particularly at night, usually special markers are interspersed with the dome-shaped bumps, often every fifth marker or so. These special markers are higher angularly shaped rigid structures, usually of plastic, having reflectors oriented toward the traffic, so that the dividing line is more brightly reflective, especially in the dark. The dome-shaped markers, though white, simply do not have sufficient reflective capability at night to be used alone.
Batterson U.S. Pat. No. 2,635,513 shows a traffic marker having a top of the general shape discussed, although the marker has a lower portion designed to be set into a bore or recess in the pavement. The Batterson marker is formed of a hard, non-elastic plastic material, and is to be filled internally with a grout material.
The principal problem with these roadway markers, or traffic "bumps", has been that they are useful only in areas receiving no appreciable snow in winter. The blades of snowplows clearing the road in winter would tear the markers loose, or the roadway simply could not be cleared. There have been a number of attempts to solve this problem. One attempted solution was to protect roadway reflectors with tapered, elongated risers positioned on either side of one or several markers, such that a snowplow blade moving in the direction of traffic would be lifted over the marker and lowered back to the surface, over a distance of a foot or so. Besides being large and expensive, another problem with these marker protectors was that they caused the snowplow to do an incomplete job of snow removal.
Other attempted solutions have taken the form of flexible or retractable markers. For example, see U.S. Pat. Nos. 1,885,941, 3,216,335, 3,901,614, and 3,920,348. None of these patents discloses a dome-shaped top which is itself deformable to accommodate a snowplow blade. Stolarczyk et al U.S. Pat. No. 3,216,335 shows a marker which is implanted in the roadway surface and has a multi-faceted, peaked top portion within which reflectors are positioned, oriented toward the approaching traffic. Besides the reflectors, the marker of that patent is comprised of a number of separate components, and thus would be fairly complex and expensive to manufacture and install. In addition, the peaked top portion with its planar sides and angled corners would last only a very short time under the punishment of a snowplow blade. The device has never been widely used on public roadways.
The remaining patents cited above show several forms of retractable marker bodies which are stated to actually recede into the pavement when struck, and they also disclose types of reflectors.
Past attempts to solve the problem of providing a flexible roadway marker useful in snowy areas simply have not been successful. Until the present invention, no suggested marker has presented a practicable and economic means for enabling the use of traffic "bumps" where snowplows are used.