Temporary Pavement Markings Placement and Removal Practices in Work Zones (2021)

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1   e use of temporary pavement markings in work zones helps delineate the vehicle path of travel and direct drivers safely through various work zone congurations such as lane changes, alignment shis, and crossovers. Agencies must consider many factors, such as work zone duration and weather conditions, in selecting appropriate pavement marking materials to eectively guide drivers through work zones. In addition, existing pavement markings need to be removed or covered in a manner that does not cause driver confusion and conict with new temporary or permanent markings. is synthesis sought to address the need for more knowledge regarding practices for temporary pavement markings and pavement marking removal in work zones. e objective of the synthesis was to review and document the policies and processes used by state departments of transportation (DOTs) for placement, maintenance, and removal of pave- ment markings in work zones. e synthesis scope encompassed multiple facets related to temporary pavement markings and pavement marking removal, including frequency of use; design considerations; performance; innovative DOT practices; and DOT policies, standards, and specications. Attainment of the synthesis objectives involved the following three major tasks: a literature review, survey of DOTs, and development of case examples through follow-up interviews. Various literature sources such as guides; research reports; journal articles; and DOT policies, standards, and specications were reviewed and compiled. In addition, an online survey questionnaire was distributed to all 50 states and the District of Columbia. Survey responses were received from all states and the District of Columbia for a response rate of 100%. Subsequent to completion of the survey, follow-up interviews to develop case examples were conducted with the following DOTs: Colorado, Florida, Illinois, Michigan, Missouri, North Carolina, and Oregon. A key nding of the synthesis is that DOTs oen have their preferred types of temporary markings, but they nd that dierent types of temporary markings are suitable for specic conditions. e type of temporary marking used in a particular work zone depends on a variety of factors, such as duration, weather conditions, frequency of snowplowing, time of year, ease of placement, pavement type, trac volumes, and equipment availability. e factors most commonly considered in selecting temporary markings are duration for the marking to remain in place, past experience, and safety. On the other hand, provisions for connected and autonomous vehicles (CAVs), which are classied based on six levels of automation and rely on image processing of pavement markings to determine the vehicle path, are rarely or never considered by 80% of DOTs when selecting temporary pavement markings for work zones. S U M M A R Y Temporary Pavement Markings Placement and Removal Practices in Work Zones

2 Temporary Pavement Markings Placement and Removal Practices in Work Zones Various types of temporary pavement markings are used in work zones, with paint and temporary tape being the most commonly applied for both asphalt and concrete pavements. Asphalt is the predominant pavement type in the United States. Thermoplastic and pre- formed plastic markings are placed infrequently in work zones. Analysis of the types of temporary pavement markings used by DOTs shows that there are some tendencies with regard to geographic distribution by climate region of the United States. For example, paint is used more frequently in the Southwest, East North Central, and Central regions, while temporary tape is used more frequently in the West and Northwest regions. Designers often select the type of temporary pavement markings to be used in a work zone, but sometimes contractors make this decision. For removal or covering of pavement markings, grinding and water blasting are the methods that are most often used, while shot blasting, black tape, and slurry seal are the least frequently applied methods. DOT specifications typically allow the use of any removal method that does not damage the surface or texture or pavement. Some DOTs place some restrictions on the methods that can be used, such as prohibitions of water blasting on asphalt pavement or limitations on the use of grinding. Contractors often select the method used to remove or cover existing pavement markings, with DOT approval sometimes required. Water blasting tends to be used more often in conjunction with frequent appli- cation of paint. As with temporary pavement markings, some general geographic trends for marking removal methods can be observed. Grinding is used more frequently in the East North Central and West North Central regions, while water blasting is used more frequently in the Southwest and West regions. A serious concern with pavement marking removal involves scarring that can generate signi ficant contrast in pavement color or texture and potentially cause driver confusion. Past experience, pavement scarring, and pavement type are the factors most frequently considered by DOTs in selecting pavement-marking removal methods, with pavement scarring taken into account by all DOTs. Some DOTs prescribe requirements for the minimum area of pavement marking removal (typically 90% or 95%) to ensure adequate removal of pavement markings or specify the maximum thickness of removal to limit damage to the pavement. Another key finding of this synthesis is that DOT standards and specifications vary significantly with respect to temporary marking layouts and dimensions, application rates, requirements for materials and construction, time considerations, basis for pay- ment, monitoring and inspection, allowable removal methods, and other factors. In general, DOTs follow the limited guidance provided in the national Manual on Uniform Traffic Control Devices (MUTCD) for temporary pavement markings and pavement marking removal, and they sometimes include additional guidance in state MUTCDs or MUTCD supplements. In addition, DOTs have developed various policies, standards, and specifica- tions for installing, maintaining, and removing pavement markings in work zones. The majority of DOTs have used or developed policies or specifications for the following requirements for temporary pavement markings and pavement marking removal: tempo- rary traffic control (TTC), minimum quality, timeline, design, and monitoring and inspection. Most DOTs use a 4-in. marking for work zones, although some DOTs use a 6-in. marking or are in the process of transitioning to 6-in. marking. DOT specifications often require temporary pavement markings to be in accordance with the manufacturer’s recommen- dations. In some cases, DOTs mandate that temporary pavement markings meet the specifications for permanent markings. In addition, some DOTs include retroreflectivity requirements for temporary pavement markings in their specifications.

Summary 3   To ensure compliance with specifications, DOTs employ various approaches to monitor- ing and inspecting temporary pavement markings, such as making the contractor respon- sible for their maintenance, requiring the contractor to meet standards in the MUTCD or quality guidelines from the American Traffic Safety Services Association (ATSSA), or mandating the contractor to appoint designated personnel responsible for maintaining temporary traffic control devices. DOTs typically inspect temporary pavement markings visually, with inspection frequencies ranging from daily to biweekly. Other aspects of DOT specifications pertain to time limitations, basis of payment, TTC, and requirements for marking removal. DOT specifications frequently prescribe assorted time limitations for temporary pavement markings, such as deadlines to install or remove temporary pavement markings and material requirements based on duration or time of year. Some DOTs also use short-term markings that must be replaced after a prescribed length of time. For basis of payment, measured pay item is typically used for installation of temporary pavement markings and pavement marking removal, while less than half of DOTs measure maintenance of temporary pavement markings for payment. For TTC, DOTs often use their typical applications for moving operations in placement of the temporary markings or marking removal. The performance of temporary pavement markings and pavement-marking removal methods was assessed through both the literature review and survey. The literature review found that there have been a few research studies that evaluated performance of temporary pavement markings, including assessments of temporary tape, paint, special color markings, and temporary pavement markings for wet, nighttime conditions. Research evaluations of pavement-marking removal methods have generally shown water blasting to be effective, while grinding leaves some scarring on the pavement. The availability of DOT performance evaluations of temporary pavement markings and pavement-marking removal methods is very limited, and these evaluations are often not documented. However, DOTs were asked to rate the performance of temporary pavement markings and pavement-marking removal methods in the survey. The DOT performance ratings show a great deal of variability for different types of temporary pavement markings and pavement-marking removal methods, suggesting a wide range of DOT experiences. For temporary pavement markings, thermoplastic and epoxy received the highest DOT performance ratings on both asphalt and concrete pavements, while tabs and temporary tape received the lowest performance ratings. DOTs noted some performance issues with temporary markings, such as paint wearing out quickly, tabs being hard to place and not staying down, extensive labor requirements for installing temporary tape, and difficulties in finding suitable temporary pavement markings for thin surface treatments on asphalt, such as chip seal, cape seal, and microsurfacing. Other challenges described by DOTs with respect to temporary pavement markings and marking removal include a need for greater awareness of weather constraints, enforcing contract provisions, maintaining temporary markings, ensuring proper engineering application of the markings, and limiting worker exposure to traffic. The pavement-marking removal methods rated the highest by the DOTs are milling, water blasting, and shot blasting. Black tape and slurry seal were rated the lowest by DOTs for both concrete and asphalt pavements. Concerns raised by DOTs about black tape in the survey comments include an observed tendency to reflect light during twilight on east–west routes, reduced performance during nighttime operations, and challenges with the tape not staying in place. DOTs believe that pavement scarring is a major concern with various pavement-marking removal methods. In addition, DOTs sometimes experience variability

4 Temporary Pavement Markings Placement and Removal Practices in Work Zones in the quality of pavement marking removal based on operator or equipment. While DOTs find that milling is effective in covering existing markings, high cost precludes its wide- spread use. To address these performance issues, DOTs are evaluating and implementing various strategies in an effort to improve temporary pavement markings in work zones, including special color markings, wet reflective markings, enhanced tape, lead and lag markings for lane shifts, foil-backed tape, abbreviated patterns for short-term markings, and a perfor- mance specification for temporary pavement markings. DOTs are also seeking innovative solutions to the problem of ghost markings created by pavement scarring when markings are removed. Strategies implemented by DOTs to address ghost markings include pattern masking, using a wider removal swath, paving over intermediate pavement layers, using temporary tape on the wearing course, and placing permanent markings in the same loca- tion as the temporary markings. While chemical removal methods have shown potential to be an innovative solution by performing well in a research setting, they have not been imple- mented by DOTs, reportedly because of a lack of contractor expertise and implementation considerations, such as speed of removal and environmental concerns. This synthesis has identified some gaps in existing knowledge, and future research needs to enhance practices for temporary pavement markings in work zones and pavement- marking removal methods in the United States. Suggestions for future research include the following: • Research to develop new materials for temporary pavement markings, such as materials for wet weather markings and thin surface treatments on asphalt pavement (e.g., chip seal, cape seal, and microsurfacing), may enhance temporary pavement-marking perfor- mance for various conditions and surfaces. • Creating a guidance document regarding the circumstances suitable for different types of temporary markings would help practitioners more readily identify appropriate temporary markings for a given situation. • Studies seeking to explore innovative methods and improve existing methods for pave- ment marking removal could lead to improved performance, especially with respect to ghost markings. • Additional field evaluations of temporary pavement markings and pavement-marking removal methods may help expand knowledge regarding their performance under dif- ferent conditions. • Advancing more uniform standards and specifications for temporary pavement markings and pavement marking removal may encourage greater consistency between DOTs, especially with respect to provisions for CAVs. • Developing a handbook on field implementation may support efforts to provide tempo- rary traffic during placement and removal of pavement markings in work zones, enforce contract provisions, achieve consistency between contractors, reduce worker exposure to traffic, and understand the constructability issues that limit the use of specific temporary marking types and marking removal methods.