Apparatus for cutting rumble strips in a road surface

Abstract

A cutting head is provided for milling rumble strip depressions in a road surface. The cutting head has a center rotational axis and a transverse diameter that varies along the length of the rotational axis so that an outer cutting surface of the cutting head defines a plane curve, such as an ellipsoid with truncated ends. The cutting head is mounted on a milling machine and rotated about the rotational axis as it is moved alternately up and down into the road surface. As the milling machine moves down the road, the movement of the cutting head creates spaced apart rumble strip depressions in the road. Because of the elliptical configuration of the cutting head cutting surface, the dimensions of the depressions can be varied along both the forward and lateral axes by simply varying the depth of cut. The curved profile of the cutting head along the rotational axis creates rumble strip depressions that avoid the sharp ninety degree corners and vertical side walls found in conventional rumble strips.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims priority from provisional application Ser. No. 60 / 333,897 filed Nov. 28, 2001 and is a continuation-in-part of application Ser. No. 09 / 783,418 filed Feb. 14, 2001 now U.S. Pat. No. 6,454,490.BACKGROUND OF THE INVENTION[0002]The present invention relates generally to road safety devices and, more particularly, to rumble strips and methods and apparatus for forming same.[0003]Depressions, commonly referred to as rumble strips or sonic nap alert patterns (SNAPS), are formed in the surfaces of roads to alert drivers when their vehicles have drifted out of the travel lane of the road or when the vehicle is approaching a dangerous portion of road, such as a stop sign or toll booth. Rumble strip depressions are typically either uniformly spaced apart or are placed in spaced apart groupings in what is known as a skip pattern. Although there is no uniform standard for rumble strips, many highway departments require a five i...

AI Technical Summary

Benefits of technology

[0012]The rumble strip depressions of the present invention have bottoms that curve along both perpendicular axes, in contrast to conventional rumble strips that curve upwardly along only one axis. The resulting forward and rearward side walls curve in a horizontal plane and, when painted with traffic paint or another light reflective coating, is more readily observable because light from vehicle headlights is reflected in multiple directions. The curved nature of the bottoms of the depressions also reduces the areas of localized stress that can lead to cracking and degradation of the road surface. Vehicle-induced wind currents more easily remove debris entering the rumble strip depressions because there are no sharp corners within the depressions where the debris can be shielded from the wind currents. The rumble strip depressions can also be easier to mill because less road material is removed in the formation of the rumble strip depressions of the present invention.

Problems solved by technology

Roller drums, however, can only be used on asphaltic roads, and the impressed depressions may tend to rebound over a period of time, thereby reducing the effectiveness of the rumble strips.

Using forms to shape the depressions is of limited applicability because the forms can only be used with wet concrete.

The vertically extending lateral walls in conventional rumble strip depressions can cause several problems.

First, when a vehicle drifts off the travel lanes and onto a rumble strip positioned on the road shoulder, the vertical lateral walls cause the tires to suddenly drop laterally from the road surface into the rumble strip depression.

This abrupt movement may pull the vehicle even further onto the shoulder and may momentarily distract the vehicle driver.

Once the vehicle tries are within the rumble strip depressions, the vertical lateral walls may cause the driver to overcorrect in an attempt to remove the tires from within the rumble strip depression.

These problems may be particularly serious for smaller cars, motorcycles and bicycles that are lighter and have smaller tires.

Another drawback of rumble strip depressions having vertical walls is the sharp 90° corner formed between the bottom of the depression and the vertical walls creates an area of localized stress that can cause cracking of the pavement.

This cracking may accelerate degradation of the road and require costly repairs or replacement of the road.

Water and other debris may also accumulate in those 90° corners and further contribute to road degradation.

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