Roadway marker

An extrudable roadway marker (11) is provided having enhanced stability. The roadway marker has a constant cross section along a centerline (A--A) that allows the roadway marker to be manufactured by extrusion. The base (13) of the roadway marker has a series of adjacent parallel grooves (27) that provide a large adhesive surface. Downwardly extending gripping edges (19) assist in attaching the roadway marker to a roadway surface. In one form, the sides of the roadway marker have reflective tape recesses (17) for receiving and protecting reflective strips 23. A raised rumble portion (15) provides a physical rumbling cue. A recess (25) reduces the weight of the roadway marker. The ends of the marker can be sheared flat or inclined. The parallel grooves may form sharp teeth where they join. The sharp teeth project away from the center of the roadway marker.

TECHNICAL AREA OF THE INVENTION 
This invention relates to roadway markers and, more particularly, to an 
extrudable lightweight roadway marker having enhanced stability. 
BACKGROUND OF THE INVENTION 
Roadway markers are utilized in a variety of traffic control applications. 
Many roadway markers are permanently affixed to a roadway to delineate 
lanes of traffic on the roadway. Other roadway markers are used to 
temporarily delineate construction or work areas. Roadway markers used in 
such applications are called temporary roadway markers. Both permanent and 
temporary roadway markers are attached to a roadway with a suitable 
adhesive. 
Permanent roadway markers remain in place and define traffic lanes, 
identify obstacles and perform other well known functions. Many permanent 
roadway markers are raised to create a rumble in an automobile when the 
tires of the automobile impact a row of markers. The most commonly used 
permanent roadway marker is formed of ceramic and has a semi-hemispherical 
or button shape. 
Temporary roadway markers serve to notify motorists that a construction 
area is near and that caution is needed. They often direct roadway traffic 
to pass along the portions of the roadway unaffected by construction, 
while protecting workers within a construction area from roadway traffic. 
After construction is completed, temporary roadway markers are loosened 
and removed. To be effective temporary roadway markers must alert traffic 
of the construction area. Typically, temporary roadway markers warn 
oncoming motorists by (1) the use of visual cues such as reflective 
surfaces, or (2) the use of physical cues such as causing a vehicle to 
rumble on contact with the marker. Both permanent and temporary roadway 
markers that provide visual cues often have a reflective surface that 
reflects light back to a driver. As noted above, physical cues are 
provided by a raised portion that causes the automobile to rumble upon 
contact with the marker. One example of a roadway marker that provides 
both visual and physical cues is described in U.S. Pat. No. 4,428,320, 
issued to Oplt et al. and entitled "Reflective Paving Marker." The Oplt et 
al. patent describes a roadway marker having a generally trapezoidal prism 
shape with a honeycombed interior, a reflective surface and raised areas. 
The honeycombed interior makes the marker lightweight, which is desirable. 
Although the roadway marker is lightweight, one disadvantage of the Oplt 
et al. roadway marker is its high manufacturing cost. Due to its 
construction, the Oplt et al. roadway marker must be injection molded. 
Injection molding is expensive when compared to other manufacturing 
processes such as extrusion. Many prior art roadway markers share these 
same disadvantages because they can only be formed by injection or some 
other molding processes. 
The present invention provides lightweight, low-cost roadway markers that 
provide a physical rumbling cue and, in some versions, a visual 
(reflective) cue. Roadway markers formed in accordance with the present 
invention have a constant cross-sectional shape throughout their length, 
which allows them to be made by inexpensive extrusion manufacturing 
processes. 
SUMMARY OF THE INVENTION 
In accordance with this invention, an extruded roadway marker is provided. 
The marker has a constant cross-sectional shape, which includes a base 
area suitable for adhesive connection to a roadway surface, and a raise 
rumble portion. The base area of the marker has a plurality of adjacent 
parallel grooves of arcuate cross section. Two parallel edges of the base 
curve downwardly for gripping the roadway. The top of the raised rumble 
portion is scalloped to reduce the weight of the roadway marker. 
In accordance with other aspects of this invention, two lateral sides of 
the raised rumble portion of the roadway marker each include a recess for 
receiving a strip of reflective tape. The other two sides may be sheared 
straight or inclined, depending upon the intended use of the marker. 
In accordance with further aspects of this invention, the teeth formed by 
the adjacent parallel grooves are sharp and project away from the 
longitudinal center of the roadway marker. 
In accordance with alternative aspects of this invention, rather than the 
lateral sides including recesses for receiving a strip of reflective tape, 
the lateral sides are inclined toward the scalloped top. If desired, the 
ridges where the lateral sides and the scallop meet can be beveled to 
reduce the abruptness of the change therebetween.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
As shown in FIG. 1, a roadway marker 11 formed in accordance with this 
invention is one integral piece having a constant cross section from one 
end of the other along a longitudinal centerline A--A. The constant cross 
section allows the marker to be extruded and sheared to the desired 
length. The roadway marker 11 illustrated in FIG. 1 has a base area 13 and 
a raised rumble portion 15. The base area 13 is substantially planar and 
of rectangular shape. The large base area allows the roadway marker to be 
strongly attached to a roadway surface by any suitable adhesive, such as 
epoxy butyl or hot melt. Two parallel gripping edges 19 located at the 
ends of wings 20, that protrude outwardly from the rumble portion 15, 
partially define the rectangular base area 13. The edges 19 are parallel 
to the longitudinal centerline A--A. Both edges 19 curve downwardly along 
their entire length, away from the substantially planar base area 13. The 
downward curvature allows for enhanced gripping of a roadway surface. More 
specifically, when an automobile tire impacts the roadway marker 11 
generally orthogonally to the longitudinal centerline A--A, the tire force 
tends to cause the edges 19 to dig into the roadway surface. Thus, the two 
gripping edges 19 facilitate the stability of the roadway marker 11. 
As shown best in FIG. 3, the base area 13 includes a series of parallel 
grooves 27. The grooves are disposed adjacent and parallel one another. 
The grooves 27 are also parallel to the longitudinal centerline A--A. The 
grooves 27 extend the entire length of the marker 11 and have an arcuate 
cross section. The arcuate cross section increases the adhesion area of 
the base 13. The larger adhesion area allows the base to be better 
attached to a roadway. Arcuate grooves provide a larger surface area for 
adhesive than do the V-shaped grooves of some prior art roadway markers. 
This translates into better roadway surface attachment. 
FIG. 4 illustrates an alternate base configuration. Like the base 
configuration shown in FIG. 3, the base configuration shown in FIG. 4 
includes a plurality of parallel grooves 31, each having an arcuate cross 
section. However, rather than the teeth created where the grooves meet 
being rounded, as shown in FIG. 3, the teeth 33 of the FIG. 4 base 
configuration are pointed, making them sharp. Further, the pointed teeth 
project away from the center 35 of the base. The sharp teeth 33 and their 
projection direction greatly improve the roadway holding power of the 
roadway marker 11. More specifically, the action of traffic causes the 
roadway marker to pull away from the adhesive that attaches the marker to 
a roadway. As the roadway marker is pulled away, the adhesive tries to 
elongate. The pointed teeth lock the adhesive into the base to improve 
adhesive performance. 
Referring to FIG. 2, the raised rumble portion 15 extends upwardly from the 
base area 13. The raised rumble portion 15 extends the entire length of 
the roadway marker 11 as measured along the centerline A--A. The raised 
rumble portion 15 has a cross-sectional shape taken in a plane lying 
orthogonal to the centerline A--A that is substantially an isosceles 
trapezoid with a scalloped recess 25 in the top surface of the trapezoid. 
This cross-sectional shape is constant throughout the entire length of the 
roadway marker 11. The raised rumble portion includes parallel lateral 
sides 17 that run the length of the marker. The lateral sides 17 are 
defined by the substantially vertical sides of the trapezoidal shape of 
the raised rumble portion. The lateral sides 17 are offset from the 
gripping edges 19 by the width of the wings 20. Thus, the width of the 
raised rumble portion 15 is less than the width of the base area 13. The 
ends of the extruded shape are, of course, sheared flat. 
The scalloped recess 25 of the raised rumble portion 15 has a continuous 
arcuate shape that is symmetrical about the centerline A--A of the roadway 
marker 11. The primary function of the scalloped recess 25 is to reduce 
the weight of the roadway marker. Thus it will be appreciated that the 
exact shape of the recess is not critical. One important aspect of the 
recess 25 is its average radius of curvature. In this regard, although the 
exact specifications of the curvature are not crucial, the average radius 
of curvature of the recess should be substantially less than the radius of 
curvature of a typical automobile tire. This prevents an automobile tire 
from seating into the recess 25 when the tire passes over the roadway 
marker 11. In one embodiment of the invention, the radius of curvature of 
the recess area is about four inches. The preferred range is two inches to 
ten inches. 
Referring to FIG. 3, the lateral sides 17 of the raised rumble portion 15 
partially form a reflective tape recesses 18. The reflective tape recesses 
18 are completed by overhanging lips 21. The overhanging lips 21 extend 
outwardly from the top of the raised rumble portion 15. The reflective 
tape recesses 18 receive reflective tape or a reflective strip 23 (not 
shown in FIGS. 1 and 2) that provides a visual cue to roadway traffic. The 
recesses 18 provide protection for the reflective tape or strip 23 from 
abrasive contact with an automobile tire. In one preferred embodiment, the 
recesses 18, and thus the lateral sides 17, are inclined from the base 13 
by an angle .alpha. of about 75.degree. to 80.degree.. It has been found 
that this angle of inclination is well suited to reflecting incident light 
from automobile headlights back to a driver. The gripping edges 19 provide 
protection for the reflective strips 23 from any adhesive that might ooze 
out. If adhesive comes in contact with the adhesive strips, the night 
reflective properties of the strips can be greatly reduced. In this 
regard, it should be noted that the reflective strips provide motorists 
guidance during the day as well as at night. More specifically, when the 
raised rumble portion 15 is installed perpendicular to the direction of 
traffic, the reflective strips provide visual cues during daytime as well 
as nighttime hours. 
FIGS. 5-10 illustrate alternate embodiments of roadway markers formed in 
accordance with this invention. In most instances, for ease of 
understanding, the same elements of the embodiments of the inventions 
illustrated in FIGS. 5-10 are identified by the same reference numbers and 
letters used in FIGS. 1-3. 
The embodiment illustrated in FIGS. 5 and 6 is substantially identical to 
the embodiments illustrated in FIGS. 1-3, the exception being that the 
ends 41 of the raised rumble portion 15 are inclined rather than 
orthogonal to the plane of the base 13 of the roadway marker. While 
various angles can be used, the presently preferred angle range, with 
respect to the vertical, angle .beta. in FIG. 6, is 40.degree. to 
70.degree., with 60.degree. being preferred. The angled ends 41 make the 
roadway marker better suited for permanent roadway marker installations 
because automobile tires hitting the ends of the marker are less likely to 
dislodge the marker. 
While the ends 51 of the roadway marker illustrated in FIGS. 7 and 8 are, 
like the embodiment of FIGS. 5 and 6, inclined, the lateral sides 53 of 
the rumble portion 15 is shaped differently. More specifically, rather 
than including a recess, the lateral sides 53 incline upwardly from the 
wings 20 to create a truncated pyramid shape having a scalloped recess 25. 
While various inclination angles can be used, as shown in FIG. 8, the 
presently preferred angle .phi., with respect to the vertical is 
60.degree.. Further, the preferred range of the radius of curvature of the 
scalloped recess is 2.5-3.0 inches. In one actual embodiment of the 
invention, the overall height (h) is 0.5 inches, the base width (w) and 
length (l) are 4.0 inches and the scallop depth (d) is 0.25 inches. 
The embodiment of the invention illustrated in FIGS. 9 and 10 is identical 
to the embodiment illustrated in FIGS. 7 and 8 except that the ridges 61 
where the scalloped recess 25 meets the inclined lateral sides 53 are 
beveled. The preferred beveled angle, .theta., is 80.degree. with respect 
to the vertical. 
Because a roadway marker 11 formed in accordance with this invention has a 
constant cross section, embodiments of the present invention can be 
manufactured by extrusion. That is, embodiments of the invention can be 
formed by extruding a suitable plastic (or metal) through a die having a 
shape corresponding to the desired cross section configuration. The 
extrudate is then cured and hardened. The manufacture of roadway markers 
using an extrusion method greatly decreases the cost of such markers. 
Moreover, an extension method allows the roadway markers of the present 
invention to be easily manufactured in varying lengths as well as with 
inclined or orthogonal end cuts. This allows embodiments of the invention 
to be used as "rumble" strips as well as spaced-apart roadway markers. The 
continuous nature of the base allows less adhesive to be used to create a 
strong bond when compared to bases that are interrupted by hollow regions, 
such as that described in the Oplt et al. patent referenced above. 
Adhesive tends to ooze into the hollows of Oplt et al. bases, reducing 
adhesive effectiveness. 
While preferred embodiments of the invention have been illustrated and 
described, it will be appreciated that, within the scope of the appended 
claims, various changes can be made therein without departing from the 
spirit and scope of the invention. Thus, it is to be understood that 
within the scope of the appended claims the invention can be practiced 
otherwise than as specifically described herein.