Striping and Pavement Markings
The Construction & Inspection and Highways Divisions are responsible for maintaining pavement markings (solid and dashed) throughout the County. When used for guidance and regulation of traffic, painted or taped pavement surfaces are traffic control devices. This includes (1) the yellow lines used for medians, passing zones and traffic flow separation in opposite directions; and (2) the white lines used for the delineation of shoulders / edge of pavement marking / channelizing islands where traffic passes on both sides in the same direction , stop bars, bicycle lanes and for crosswalks. All surfaces are swept via the use of contractor’s and/or rental broom trucks prior to painting. In addition, the County inspectors require a test pattern to be painted to determine that the proper width, spacing, thickness, bead spray and general painting pattern is achieved.
Maintaining pavement markings is quite expensive. The 2019 program cost approximately $0.04 – 0.05/ft and painted approximately 284 miles or 3,691,000 linear feet of road. A portion of this program went into durable marking work (preformed thermoplastic markings) which are used for stop bars, advance railroad crossing markings, crosswalks, turn arrows, "ONLY"s and other words, as well as channelizing lines. The calendar year 2018 program completed approximately 1,000,000 linear feet.
Several factors effect the durability of painted pavement markings. Some of these are the traffic volume, the number and severity of snow storms (sanding roads wears the markings faster), curves in the road (traffic tends to cut the corner slightly), age of the pavement (newer pavements absorb more paint leaving less on the surface where needed), and paint formulation. St. Mary’s County is using an oil based paint which is more durable and less expensive than a latex based paint and less durable than an epoxy based paint.
Roads are repainted, typically between August and September, as the stripes get worn by traffic. Most roads require striping yearly while some require striping twice a year. The striping program also stripes some of the roads involved in the Division’s maintenance overlay program. Roads with a fresh chip seal surface usually require two paint applications on the road centerline.
All pavement markings are retro-reflective, meaning they reflect light from headlights back toward the driver. This retro-reflectivity is accomplished through the introduction of glass beads into the wet paint. When the paint dries, the beads are trapped throughout the thickness of the paint. As the paint line wears the beads on the surface wear off, while new beads are being uncovered.
Pavement markings need to be applied as needed based on traffic volumes, paint condition and under other specific warrants. All County roadways classified as a major collector or higher require both edge markings and line striping. To ensure the success of the program, reflectivity shall be 84 for the white and 55 for the yellow paint with both applications maintaining a no-tracking time of sixty (60) seconds or less. Glass beads must also meet the MUTCD reflectivity requirements and shall be retro-reflective Type 1 Gradation A. Paint is applied at a 15 mil. wet / 12 mil. dry thickness and the beads are applied at a rate of six (6) pounds to eight (8) pounds per gallon of paint. Over 3,600,000 linear feet of 4” wide centerline and edge striping exists on the County roadway system. The Department has found that the use of edge striping along roadways that are subject to periodic flooding greatly improves the drivers ability to safely negotiate these areas during inclement weather and flooding conditions.
Raised Pavement Markers (RPM's)
Rural roads can benefit from many different low-cost traffic engineering improvements. Pavement markings provide an important means of communication and guidance for all roadway users and must be capable of conveying information during inclement weather and evening hours when there may be little to no contribution from overhead lighting. Standard pavement markings are often obscured by rain or snow making lane delineation difficult. Therefore, Raised Pavement Markers (RPMs) are often used to supplement and increase the visibility of conventional markings. They should be the same color as the pavement markings they supplement (except on divided roadways, where the backside facing wrong-way traffic may be red). Although raised pavement markers (RPMs) provide enhanced delineation during inclement weather and evening hours, studies have shown that these markers are susceptible to damage from winter maintenance practices (ie. snow plowing).
Since St. Mary's County is in a snow zone, it is necessary to utilize a more expensive snow-plowable raised pavement marker (SRPM). These special RPMs have metal rails on both sides of the assembly that are designed to lift a snowplow blade up and over the retroreflectors. The markers are also typically recessed into pre-existing pavement by a "groove" that is mechanically cut into the existing pavement (see photo) to further minimize exposure above the roadway surface. SRPMs are cast iron markers that are held into place with a two part epoxy. Research also has concluded that the best use of SRPMs is recommended in high accident locations or areas where geometric conditions require enhancement of standard traffic marking systems. In August 2009, the DPW&T completed the installation of an SRPM pilot program on portions of Mechanicsville and Golden Beach Roads. The raised markings will provide both wet and dry reflectivity, increase driver preview time and provide driver’s with supplemental visual information in order to maneuver more safely and effectively.
In accordance with the Maryland Manual of Uniform Traffic Control Devices (MUTCD) and the Maryland Vehicle Law, all traffic control devices shall be installed in accordance with the warranting criteria and standards of the MUTCD. The current 2011 edition specifies center line under the following conditions:
Center line markings shall be placed on all paved urban arterial and collectors that have a traveled width of 20 feet or more and an ADT of 6,000 vehicles per day or greater. Center line markings shall also be placed on all paved two-way streets or highways having three or more traffic lanes. Center line markings should be placed on all rural arterials and collectors that have a traveled width of 20 feet or more and an ADT of 4,000 vehicles per day or greater. Center line markings should also be placed on all rural arterials and collectors that have a travel width of 18 feet or more and an ADT of 3,000 vehicles per day or greater. Center line markings should also be placed on other traveled ways where an engineering study indicates such a need. Engineering judgment is required to determine if center line should be placed on roadways less than 16 feet in width. In general, center line pavement markings are discouraged on low volume residential streets, especially if the portion of roadway on which a center line is proposed is below 600 vehicles per day. Many citizens perceive that the pavement markings detract from the attractiveness of their neighborhood, and actually encourage speeding. In addition, center line should generally not be used to discourage on-street parking unless traffic volumes or sight distance restrictions indicate the need for two unobstructed lanes of travel. Roadways classified as local streets would not generally be marked. Minor collector streets are optional, and will require justification. Major collectors and arterials generally will warrant center line and edge line pavement markings
Based on the above, 30 days prior to installing new pavement markings on roadways with an ADT less than 3,000 vehicles per day, documentation of the need for the markings with respect to warrants in Chapter 3 of the MUTCD must be prepares and submitted to the Deputy Director for approval. Supporting information shall include the road name and type/limits of marking, the width of the roadway, average daily traffic volume (estimate by multiplying the number of homes by 10 on a single access if a traffic count is not available), speed study if needed (contact Division of Highways), and any other relevant information, including photographs.
Maintenance of Traffic
Traffic must be maintained at all times by the contractor. A combination of traffic cones (18” in height), barrels (orange and white) for lane delineation, barricades, flashing arrow units (mandatory on all multi-lane roads) for early warning at lane enclosures and a “chase truck” with appropriate warning lights and signs is required to keep traffic out of the fresh paint to avoid tracking.