Pavement markings are a critical element of
the roadway system, providing guidance to roadway users and optimizing
roadway efficiency, both in the daylight and at night. Major marking
types include centerlines, lane lines, two-way left-turn lane
lines, and edge lines, or long-lines, as well as stop bars and crosswalks,
or short-lines. Pavement markings can be installed using a number
of different marking materials. When
used properly, pavement markings enhance roadway safety and efficiency.
The Traffic Engineering Division maintains
the roadway striping on all streets within the city limits (almost
two million linear feet of markings), except for state highways. At
signalized intersections on state highways, the City also maintains
the crosswalk and stop bar markings. State highways include Wadsworth
Boulevard (SH 121), Kipling Street (SH 391), Colfax Avenue (US 40),
6th Avenue (US 6), Morrison Road (SH 8), and Hampden Avenue (US 285).
To report pavement-marking problems on a state highway, please ca
ll the Colorado Department of Transportation (CDOT) at 303-757-9511.
To report pavement-marking problems on any
other roadway within the City, please call 303-987-7980.
Marking Types
A Federal standards document, the Manual of Uniform Traffic
Control Devices (MUTCD) guides all agencies in the color and types
of markings that can be used to mark the roadways. Yellow lines delineate
the separation of traffic in opposite directions or mark the left
edge of the pavement on divided roadways, one-way streets, and ramps.
White lines delineate the separation of traffic in the same direction
or mark the right edge of pavement. Other colors, such as red and
blue can be used typically in parking lots, where for example blue
is used as a background color for wheel chair (handicap) markings.
The MUTCD also establishes guidelines for the
widths and patterns of pavement marking lines. Broken lines are permissive
in character, indicating that it is common for drivers to cross the
lines. Solid lines are restrictive in character, indicating that crossing
of the line is not desirable. Double lines indicate maximum restrictions
or prohibitions, width of lines indicate the degree of emphasis or
importance.
Marking Materials
Many types of marking materials are available,
each having different properties, and include:
The City of Lakewood uses all of these types
of materials to maintain visible lines on your City streets.
Paint. Hot-applied,
water-based paint is used for the great majority long-line markings
on roadways within the City of Lakewood. Painted lines are applied
approximately 15 mils thick (a mil is one thousandth of an inch in
thickness) and achieve retroreflectivity
through glass beads that are sprayed onto the freshly painted line.
In terms of initial cost, paint is the most economical pavement marking
to use, however it has the shortest functional life. Pavement marking
crews in Lakewood strive to paint each street twice a year, once in
mid- to late spring (after snowplowing and sanding operations are
over) and once in the fall.
When
you see our paint vehicles on the road, please stay off the wet lines
and observe the directions on the back of the paint and follow trucks.
The paint is easily removable from surfaces with soap, water, and a
little elbow grease, however when tracked through by impatient drivers,
the retroreflectivity is compromised and the roadway must be repainted.
Remember, it is illegal to cross the freshly painted lines and you could
be issued a citation.
Hot
Thermoplastic. Hot thermoplastic is applied as long- and short-lines
on newly chip-sealed roadway surfaces in Lakewood. Thermoplastic lines
are applied between 60 and 90 mils in thickness and also achieve retroreflectivity
from glass beads sprayed on the freshly marked lines. On chip-sealed
roadways, the hot applied thermoplastic has the ability to flow into
the chip and form a long lasting line. On smooth asphalt or concrete
surfaces, thermoplastic lines protrude above the surface and are subject
to removal by plow blades during snow removal. For this reason, hot
thermoplastic is not used extensively in Lakewood.
Preformed
Plastic Tape. Preformed plastic tape can be inlayed on new roadway
surfaces or surface applied to existing surfaces to create either short-
or long-lines markings. Plastic tape is an engineered material, 60 mils
in thickness and is manufactured with embedded glass beads to provide
a consistent retroreflectivity. While the City of Lakewood uses both
installation methods, the majority of tape installations have been long-
and short-lines completed in conjunction with asphalt resurfacing projects.
Inlayed tape has a considerably longer useful life than paint or thermoplastic,
providing adequate marking essentially for the life of the pavement
surface. Surface applied plastic tape is susceptible to removal and/or
tearing by snowplow blades similar to hot thermoplastic.
Preformed
Thermoplastic. Preformed thermoplastic
is "melted" or burned down onto new or existing roadways to
create stop bars and crosswalks. Preformed thermoplastic tape is also
a manufactured material, about 60 mils in thickness. The City of Lakewood
uses this marking material to maintain the crosswalk and stop bars on
arterial roadways. Preformed thermoplastic has a much longer life than
paint, however is also somewhat susceptible to snow plow blades.
Retroreflectivity
Pavement markings must serve their purposes of
providing driver guidance and roadway efficiency both during the day
and at night. Retroreflectivity is the property that allows drivers
to see pavement markings in the dark. Light from the driver's headlights
is bounced back to the vehicle rather than reflected away, as shown
in the following illustration
Light from a vehicle's headlights enters a glass
bead in the pavement marking material, is bent downward by the bead.
Light striking the back of the bead, embedded in the paint, is then
reflected back to the light source. This occurs in each of the thousands
of glass beads, resulting in illumination of the pavement marking line.
The preformed marking materials have the beads
manufactured into the material, providing more consistent, longer lasting
retrotreflectivity. Paint, given the opportunity to adequately dry,
provides good retroreflectivity until traffic wears off the beads, typically
a period of four to six months. However, driving through wet roadway
paint removes the majority of beads and destroys the retroreflectivity
of the pavement marking, creating the need for the roadway to immediately
be repainted.