Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
1 Introduction While the need to remove pavement markings may occur during the end of the service life of a marking, it is also common to remove or obscure markings due to construction work that requires lane shifts or changes in the traffic pattern. Pavement 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 effectively 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 marking 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 discoloration 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 2009 Manual on Uniform Traffic Control Devices (MUTCD) addresses pavement mark- ing removal in two sections as seen below. Section 3A.02 Standardization of Application Standard: Markings that are no longer applicable for roadway conditions or restrictions and that might cause confusion for the road user shall be removed or obliterated to be unidentifiable as a marking as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Markings Standard: For long-term stationary operations, pavement markings in the temporary traveled way that are no longer applicable shall be removed or obliterated as soon as practical. Pavement marking oblit- eration 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 scarring, the removal may result in insufficient pavement marking removal. A compromise S U M M A R Y Effective Removal of Pavement Markings
2between complete removal and limiting pavement damage needs to be made in most situa- tions. 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 tech- niques are available; (b) what the trade-offs are of each technique with respect to effec- tive 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. The objective of this research was to determine best practices for the safe, cost-effective, and environmentally acceptable 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 Phase I research focused on the identification, description, and evaluation of available and emerging removal processes. Phase I was carried out through a literature review of past research that evaluated pavement marking removal techniques and a nationwide survey of transportation practitioners. The survey conducted in the Phase I research also focused on the current state of the practice of pavement marking removal. The survey was distributed to each state department of transportation (DOT), to over 100 cities nationwide, and to practi- tioners through many listservs and other contact lists. The survey yielded 55 responses from a combination of state and local agencies as well as contractors, equipment manufacturers, and industry groups. The Phase II research used results from Phase I to develop a field study to evaluate vari- ous combinations of pavement marking removal. The removal combinations to be evalu- ated were based on combinations of the type of removal process, type of marking material, and type of road surface. The field study consisted of two different study types. The first study type was controlled pavement marking removal evaluations where the researchers controlled the marking types, road surfaces, and removal methods used. The second study type was the evaluation of pavement marking removal operations as part of planned high- way maintenance or construction as they occurred or after they were recently completed. In addition to the field studies, the research team explored several other areas of pavement marking removal. These areas were the environmental and worker safety issues associated with marking removal, the removal of temporary tape pavement marking materials, and the usage of masking and blending techniques to either cover markings or help conceal removed areas. Findings and Conclusions The literature review, survey, controlled test deck removal, field observations, and addi- tional research areas all yielded information used in the findings and conclusions of the research. The researchers developed a standalone table of pros and cons of the most com- mon forms of pavement marking removal (Appendix E). This table highlights the advan- tages and disadvantages of each removal technique, which should aid in the selection of the most appropriate removal technique. The survey responses indicated that grinding was the most common form of pavement marking removal and that it was preferred by many, even though most noted the drawbacks of pavement scars that are often left behind. Water blasting was also commonly used and is becoming more common as more equipment makes its way to the field. Water blasting was
3 the most common method that the survey respondents would like to try. Both sand and shot blasting were commonly used, but they also both received several responses that indicated they were no longer being used. Outside of those four removal techniques, the temporary masking of markings was the only other method regularly used in the field. Other removal methods, such as chemical, heat, and laser, and other forms of blasting, such as soda, dry ice, or glass, are not commonly being used. Grinding removal is the most available removal technique and is also the least expensive type of marking removal. Water blasting systems are becoming more common, but avail- ability is limited in some areas. Water blasting is more expensive than grinding. The sur- vey responses and literature review indicated water blasting can average being from 10 to 40 percent more expensive than grinding. The cost of removal is highly dependent on the availability of equipment and size of the removal contract. Typically, only grinding and water blasting are used for long stretches of removal because they can remove marking at a greater rate than other techniques. Other removal techniques such as shot and sand blasting as well as grinding and water blasting are used for shorter removal sections. There are methods of applying durable coatings over the markings to blend into the appearance of the pavement. The problem is that these coatings and the surrounding pave- ment may change colors at different rates over time, and the covered area will no longer blend as well as it did originally. The surface texture of the painted areas and the surround- ing pavement will also be different and may be noticeable under certain driving conditions, such as the sun being low on the horizon or in wet conditions. Simply covering the markings with a durable material also leaves the possibility that the marking may later be exposed and need to be either removed or recovered with another durable material. Subsequently, the MUTCD only allows the markings to be covered for temporary conditions. Color-matching paint systems may be better suited in a light application over removed areas in the short term to help blend in color differences after removal until the removed area has time to age and blend into the surrounding pavement. Any materials placed over a marking to mask it need to be maintained so that the marking does not become exposed over time. The survey responses indicated that after the removal of pavement markings, fog or slurry seals have been used to help blend the removed areas with the surrounding pavement sur- face. The use of a fog seal or slurry seal to help blend color changes, scars, or surface texture changes to the surrounding pavement would only be useful on asphalt road surfaces. The researchers propose that on concrete surfaces where a discoloration occurred after marking removal, a larger area could be washed or cleaned with a high-pressure water blasting system to help blend in the removed area to the surrounding pavement. The field studies indicated that when the sun is behind the viewer, it makes the removal area more visible by lighting up the unremoved marking and reflecting off the textured surface. When looking toward the sun, there is glare off smooth surfaces, and textured surfaces look dull. Using a technique such as a fog seal or water blasting on a larger area will reduce visibility issues associated with the sun because the area will be more uniform in appearance. The MUTCD indicates the need to remove or obliterate markings until they are unidenti- fiable as markings. There are not standards for acceptable levels or criteria for how to deter- mine a marking is no longer identifiable. The level of removal needed to make a marking no longer identifiable will differ for each situation. White markings on lighter-color road sur- faces will not require the same level of removal as white markings on a dark surface. Remov- ing a marking to the point of making the marking itself no longer identifiable may result in damage to the road surface that could be confusing to drivers. The MUTCD indicates that the removal of the marking should minimize pavement scarring. Again, there are not standards for acceptable levels or criteria for how to determine scarring. The wording in the MUTCD regarding how to minimize scarring acknowledges that when removing pavement
4markings, some scarring may occur. It is the agenciesâ job to ensure that appropriate pave- ment marking removal practices are used to minimize the scarring while removing enough of the marking material to no longer be considered as guidance or be confusing to drivers. In general, the state DOT specifications call for the complete removal of the mark- ings while limiting damage to the road surface. Several states did call for specific levels of required removal ranging from 75 to 100 percent, with the majority indicating 90 or 95 percent removal. Several states also indicated maximum allowable depth of pavement scar- ring ranging from Â¹â16 to Â¼ inch, with the majority indicating Â¹â8 of an inch or less. The survey responses did acknowledge the need for a balance between the removal percentage and dam- age to the road surface. The thought is that to attain 100 percent removal, excessive damage to the road will occur, whereas 90 or 95 percent removal may do minimal damage to the road surface. Leaving marking material on the road surface or damaging the road surface will both be visible to drivers, so an adequate balance needs to be sought for each individual situation. The required level of pavement marking removal should vary depending on the reason for the removal and the roadway conditions where the removal takes place. The controlled field test deck removal and field observations found many good and some bad pavement marking removal results. High-pressure water blasting provided good removal on the Portland cement concrete (PCC) surfaces with little damage to the road surface and good removal of the marking materials. On asphalt surfaces, the results were mixed. The system typically removed all of the marking, but in some test areas, the high-pressure water blasting system removed some of the surface asphalt and fines. The flailing truck had mixed results on both the PCC and asphalt surfaces. To achieve a high level of removal, the flailing truck typically left a scar on the road surface. Minimal scarring may be okay in some areas, but in critical areas such as lane-shift areas, scarring needs to be minimized as much as pos- sible. The speed of removal depended on the marking type and the quality of the removal. The water blasting was as fast as or faster than the grinding for many of the tests. The orbital flailing system was not as aggressive as the full-size truck drum flailing system, and so it left minimal scarring on the road surface. The drawback to this was the system seemed to have difficulty removing paint and preformed thermoplastic markings that found their way into voids below the pavement surface. The orbital flailing system was not a full-size system, which resulted in much slower removal than the other full-size removal methods tested. Recommendations The recommendations include things to consider that relate to pavement marking removal and a set of best practices to assist in improving pavement marking removal quality. The standalone table of pros and cons of the most common forms of pavement marking removal in Appendix E should be used to help determine which type of pavement marking removal may be best suited for a given situation. The selection of a removal system needs to take into account many factors, each of which may be more or less influential on some projects. The proper consideration of each of these factors is the best way to achieve acceptable pavement marking removal results. These factors include the following: â¢ What marking material is being removed. â¢ What road surface the material is on. â¢ How much of the material needs to be removed (what is the purpose of the removal). â¢ Whether speed of removal is important. â¢ What removal techniques are available and at what cost. â¢ Whether there are special environmental conditions that need to be considered.
5 â¢ How long the removed area will be viewed by drivers (whether a new surface will be installed or markings will be restriped in the future). â¢ Whether the removed area will be in a location where confusion could lead to an accident. â¢ Whether there are other measures that can be taken to minimize confusion to the driver. Best Practices Pavement marking removal should be specified as a percentage of material removed based on the purpose of the removal. The percentage of material removed equates to the percent- age of the road surface made visible where the marking was removed. The purpose of the removal should also play a role in the removal method selected and other measures selected to provide a roadway with delineation that is not confusing to drivers. Changing pavement marking patterns is the most critical pavement marking removal because the old markings are no longer conveying the travel path to the drivers. Any errors in removal can lead to drivers being confused by the old markings or the removed areas. A high percentage of the material needs to be removed, but damage to the road surface also needs to be considered. Removal should be 90â95 percent, with 100 percent removal in some cases. Based on current practice, damage to the road surface should be Â¹â8 of an inch or less while changing the road surface texture as little as possible. Open-graded or tined surfaces may require the material below the pavement surface to be removed with a blasting technique to minimize scarring. Depending on the road surface type and the road conditions, additional measures may need to be taken to reduce driver confusion with the removed markings. These additional measures can include fog or slurry seals over the removed area or the entire lane width on asphalt surfaces. The friction of the road surface needs to be considered, but these techniques will help blend the removed areas with the surrounding pavement. On PCC surfaces, additional light removal around the removed area or across the entire lane width can be conducted with a blasting technique such as water blasting to help blend in the removed area. Remove and replace is the process of removing the current pavement marking material and restriping in the same location where removal occurred. This type of removal is conducted to remove a poorly bonded material so the new material can form a good bond, to reduce the overall thickness of restriped markings, or to remove an aged marking that is incompat- ible with the new marking that is being applied. For remove and replace with compatible markings, the whole marking does not always need to be removed, so removal can be limited to at or above the road surface. This can help limit scarring to the road surface. Removal by grinding may be the best option, but if full removal or removal of material below the surface is needed, then water blasting or another blasting technique may be a better option to minimize scarring. Practitioners need to consider the work phasing and the final road surface. If markings are to be removed for a short duration prior to a new surface, then damage to the road surface is not as critical compared to a removed area that will be visible for a longer duration. Any removal on the final road surface needs to be accomplished with minimal damage to the road surface. It may be best to use temporary pavement markings on the final road surface until the final marking configuration so that removal will do as little damage to the road surface as possible. The selection of the most appropriate pavement marking removal system needs to consider the amount of removal that is required and the length of time available to complete the removal. If the removal quantity is large, full-size removal trucks should be used. If the removal quantity is small, hand units and the slower removal methods can be considered.
6Symbols and text should be removed in a square or rectangular pattern so that the previous shape is not left as a scar or discoloration. This requires removal of the marking and the nec- essary removal/cleaning around the marking to help blend in the area with the surrounding pavement by creating a larger removal area that is no longer recognized as a symbol or text. Older road surfaces that are experiencing cracking or surfaces with joints may need spe- cial consideration when removal occurs around these areas. The use of high-pressure water blasting on these surfaces can lead to road damage if the water is allowed to penetrate into the cracks or joints. Grinding may also pose a threat to cracks and joints. Removal around these areas should be conducted carefully such that the joints are not disturbed and that the cracks are not made worse by the removal. Initially, any pavement marking removal project should begin with testing the removal equipment in a non-critical area to evaluate the removal. This initial testing will show how well the operators can use the equipment to remove the marking material and how much damage is done to the road surface. The test area can be used to adjust the equipment to find the ideal setup for the work required. If the operator and equipment cannot provide satisfactory results, another removal system should be considered. The quality of removal needs to be evaluated during the day, at night, and during wet conditions. Surface color changes and scarring will have a greater impact during the day than at night, whereas retroreflectivity from remaining marking material or retroreflectivity differences because of surface texture changes will be more noticeable at night. The direction of travel and the position of the sun also need to be considered. Wet conditions may fill pave- ment scarring, resulting in an area that looks like a wet marking and thus creating confusing delineation. Any areas with color, texture, or retroreflectivity issues should be corrected to reduce or eliminate driver confusion. Pavement marking specifications for areas where removal has occurred should consider post-removal conditions. Wider markings and continuous markings in transition areas will provide better guidance to drivers and may reduce confusion of the removed marking areas by enhancing the new markings. Markings with high retroreflectivity levels should also be maintained in areas where previous removal could lead to confusion by drivers at night. The high retroreflectivity of the new markings will be more noticeable to drivers than removed areas of markings with lower retroreflectivity levels.