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7 While the need to remove pavement markings may occur during the end of the service life of a marking, it is also com- mon to remove or obscure markings due to construction work that requires lane shifts or changes in the traffic pattern. Pave- ment markings that were previously used as guidance need to be removed or obscured so that new markings can be applied to form the new traffic pattern. Markings that are not effec- tively removed or obscured can be confusing to drivers and create an unsafe driving environment. Ineffective pavement marking removal results in at least two primary outcomes: (1) the marking is not completely removed and results in a mark- ing that may suggest the original travel path is still the intended travel path, or (2) the marking is completely removed, but the removal technique has produced a scar or surface discolor- ation that provides a significant texture or color contrast with the surrounding pavement surface that may also suggest the original travel path is still the intended travel path. The Federal Highway Administration (FHWA) Manual on Uniform Traffic Control Devices (MUTCD) addresses pavement marking removal in two sections as seen below (FHWA 2009). Section 3A.02 Standardization of Application Standard: Markings that are no longer applicable for roadway conditions or restrictions and that might cause confusion for the road user shall be removed or obliterated to be unidentifiable as a marking as soon as practical. Option: Until they can be removed or obliterated, markings may be temporarily masked with tape that is approximately the same color as the pavement. Section 6F.77 Pavement Markings Standard: For long-term stationary operations, pavement markings in the temporary traveled way that are no longer appli- cable shall be removed or obliterated as soon as practical. Pavement marking obliteration shall remove the non-applicable pavement marking material, and the obliteration method shall minimize pavement scarring. Painting over existing pavement markings with black paint or spraying with asphalt shall not be accepted as a substitute for removal or obliteration. Option: Removable, non-reflective, preformed tape that is approximately the same color as the pavement surface may be used where markings need to be covered temporarily. The MUTCD does not address how to determine if a removed marking is unidentifiable or what measures should be used to evaluate whether a removal technique is able to minimize pavement scarring. Not addressing these two issues results in a variable quality of pavement marking removal. If an agency establishes a requirement for 100 percent marking removal so that the marking is unidentifiable, the resulting removal may produce an excessive amount of pavement scarring. In contrast, if an agency establishes a policy of minimizing pavement scar- ring, the removal may result in insufficient pavement marking removal. A compromise between complete removal and lim- iting pavement damage needs to be made in most situations. This is a difficult problem that is faced by every transportation agency. This is further compounded by the lack of sufficient guidance on the following: (a) what removal techniques are available; (b) what the trade-offs are of each technique with respect to effective removal versus the amount of scarring; and (c) whether any of these techniques could be combined to improve the percentage of material removed, reduce the scarring, and/or reduce the process time and/or cost. Objectives The objective of this research was to determine best prac- tices for the safe, cost-effective, and environmentally accept- able removal of work zone and permanent pavement markings with minimal damage to the underlying pavement or visible character of the surface course. The research was divided into two phases over the duration of the project. Phase I of the research focused on collecting information on pavement marking removal techniques and past experiences through a nationwide survey and a literature review. Phase II evaluated the pros and cons of the different removal techniques. The C H A P T E R 1 Introduction
8work of both phases resulted in developing recommendations of best practices for the removal of pavement markings. The objective itself has many aspects that needed to be eval- uated to determine the best practices for pavement marking removal. The most critical aspects are posed below as ques- tions that needed to be answered by the two phases of the research. â¢ What are the current and emerging mechanical, chemical, and/or obscuring methods of pavement marking removal? How common are each of these techniques? â¢ Are there mechanical processes, such as a combination of heat and power tools that can effectively remove the markings? â¢ Are certain mechanical processes more effective for spe- cific markings and/or road surface types? What are the drawbacks of the different processes? â¢ Are there chemical removal systems that are environmen- tally acceptable, and how effective are they? â¢ Does mechanical removal of certain marking systems pose an environmental risk? â¢ Is the preferred removal technique readily available and of a reasonable cost for materials, equipment, and labor? â¢ Are there methods of applying a durable or temporary coat- ing over the existing pavement marking that will blend in to the appearance of the pavement, perhaps by using color- matching technology or a camouflaging technique? Or can the full width of the pavement be covered completely in a cost-effective manner without losing friction characteristics? â¢ Can a combination of mechanical processes and obscuring methods result in a more effective removal of the marking? â¢ Are there color-matching paint systems that can help obscure scars left by mechanical removal techniques? â¢ How much removal is adequate to meet the MUTCD requirements? â¢ How much tolerance is there for altering the pavement surface? â¢ Does the removed marking leave a ghost marking or alter the road surface as compared to the surrounding surface? Is the ghost marking or altered road surface more or less visible in different light conditions or in wet conditions? â¢ What are the best ways to measure the effectiveness or quality of marking removal with respect to quantifying whether a removed marking is unidentifiable, and whether the removal minimized pavement scarring?