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

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92 Conclusions Synthesis Objectives, Scope, and Methodology e objective of this synthesis was to determine the existing state of the practice by depart- ments of transportation (DOTs) for placement, maintenance, and removal of pavement markings in work zones. e synthesis scope included design considerations, DOT policies and specications, selection processes, performance, and innovative solutions. e synthesis included any type of material used to delineate the path of travel in a work zone before the placement of permanent pavement markings and any method used to obliterate or cover existing pavement markings, including both temporary pavement markings and permanent pavement markings. Methods used to achieve the synthesis objectives included a literature review, survey questionnaire, and follow-up interviews. Various sources such as guides; research reports; journal articles; and DOT policies, standards, and specications were reviewed and compiled. An online survey questionnaire was distributed to all 50 states and the District of Columbia. Survey responses were received from all 51 agencies for a response rate of 100%. Case examples were developed through follow-up interviews with Colorado, Florida, Illinois, Michigan, Missouri, North Carolina, and Oregon. Summary of Key Findings Key ndings from the synthesis based on the literature review, survey results, and follow-up interviews are described in the following sections, which are organized by topic. DOT Experiences with Temporary Pavement Markings and Pavement Marking Removal • Designers usually select the type of temporary pavement markings to be used in a work zone, but sometimes contractors make this decision. • Paint and temporary tape are the most frequently applied temporary pavement markings in work zones for both asphalt and concrete pavements, with asphalt being the predominant pavement type in the United States. Example situations in which temporary tape is used include markings crossing a permanent surface at an angle, TTC phases prior to the nal construction phase, and during winter months. ermoplastic and preformed plastic mark- ings are the least commonly implemented types in work zones. • While DOTs oen have their preferred types of temporary markings, they nd that dierent types of temporary markings are suitable for specic conditions, and the type of temporary marking used in a particular work zone depends on a variety of factors, such as duration, C H A P T E R 5

Conclusions 93   weather conditions, frequency of snowplowing, time of year, ease of placement, pavement type, traffic volumes, and equipment availability. The factors most commonly considered in selecting temporary markings are duration for the marking to remain in place, past experi- ence, and safety. • Provisions for CAVs, which are classified 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. • Grinding and water blasting are the methods for pavement marking removal that are most often used, while shot blasting, black tape, and slurry seal are the least frequently applied methods. Water blasting tends to be used more often in conjunction with frequent application of paint. • Past experience, pavement scarring, and pavement type are the factors most frequently con- sidered by DOTs in selecting pavement-marking removal methods, with pavement scarring taken into account by all DOTs. • Contractors often select the method used to remove or cover existing pavement markings. In some cases, DOT approval is required, and standard specifications sometimes prohibit the use of specific methods based on pavement type. • Contractor and equipment availability sometimes limits the range of temporary pavement markings or pavement-marking removal methods available to DOTs. • Analysis of the types of temporary pavement markings and marking removal methods 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. For marking removal, 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. • Challenges described by DOTs with respect to temporary pavement markings and marking removal include a need for greater awareness, weather constraints, enforcing the contract provisions, maintaining temporary markings, ensuring proper engineering application of the markings, ghost markings, and limiting worker exposure to traffic. • DOTs are interested in finding out about practices and experiences of other DOTs for temporary pavement markings and marking removal, especially with respect to performance, selecting marking types for different surfaces, placement under high speeds and traffic volumes, preparing for CAVs, materials, time constraints, enforcing contract provisions, using innovative types of markings, wet applications, and delineating shoulders. DOT Policies, Standards, and Specifications for Temporary Pavement Markings and Pavement Marking Removal • In general, most DOTs adopt the limited guidance provided in the national MUTCD (FHWA 2009) for temporary pavement markings and pavement marking removal, along with their own policies, standards, and specifications. Some DOTs amend the national MUTCD guidance in their own MUTCDs or MUTCD supplements. • The majority of DOTs have used or developed policies or specifications for the following requirements for temporary pavement markings and pavement marking removal: TTC, minimum quality, timeline, design, and monitoring and inspection. • 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 payment, monitoring and inspection, allowable removal methods, and other factors.

94 Temporary Pavement Markings Placement and Removal Practices in Work Zones • For temporary pavement markings in work zones, most DOTs use a 4-in. marking, 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 recommendations. In some cases, DOTs mandate that temporary pavement markings meet the specifications for permanent markings. • Some DOTs include retroreflectivity requirements for temporary pavement markings in their specifications. Initial threshold values vary among DOTs (between 150 and 2,700 mcd/m2/lx for white temporary pavement markings and between 125 and 2,400 mcd/m2/lx for yellow temporary pavement markings) and are often based on marking color, material type, and time after placement. • DOTs typically perform inspection of temporary pavement markings visually with inspection frequencies ranging from daily to biweekly. • DOT specifications include different approaches to the monitoring and inspection of temporary pavement markings, such as making the contractor responsible for their main- tenance, requiring the contractor to meet standards in the MUTCD or ATSSA quality guidelines (FHWA 2009, ATSSA 2014), or mandating the contractor to appoint designated personnel responsible for maintaining TTC devices. • DOT specifications frequently prescribe assorted time limitations for temporary pave- ment 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, which must be replaced after a prescribed length of time. • Measured pay item is typically the basis of payment used by DOTs for installation of temporary pavement markings and pavement marking removal. Less than half of DOTs measure maintenance of temporary pavement markings for payment. • DOTs often use their typical applications for moving operations in placing the temporary markings or marking removal. • For removal methods, the DOT specifications typically allow the use of any 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 prohibiting water blasting on asphalt pavement or limiting the use of grinding. • Some DOTs prescribe minimum requirements for the amount of pavement marking removal (typically 90% or 95%) or limit the thickness of removal. Performance of Temporary Pavement Markings and Pavement-Marking Removal Methods • Thermoplastic and epoxy received the highest DOT performance ratings for both asphalt and concrete pavements, while tabs and temporary tape received the lowest performance ratings. • DOTs experience 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 such as chip seal, cape seal, and microsurfacing. • There have been a few research studies to evaluate performance of temporary pavement markings, including assessments of temporary tape, paint, special color markings, and temporary pavement markings for wet, nighttime conditions. • 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.

Conclusions 95   • DOTs nd that pavement scarring is a major concern with various pavement-marking removal methods. Other performance issues noted by DOTs include pavement discoloration from water blasting and black adhesive residue from temporary black tape. • DOTs nd that milling is eective in covering existing markings, but high cost precludes its widespread use. • DOTs sometimes nd that there is variability in the quality of pavement marking removal based on operator or equipment. • Research evaluations of pavement-marking removal methods have generally shown water blasting to be eective while grinding leaves some scarring on the pavement. • ere is a great deal of variability in the DOT performance ratings for dierent types of temporary pavement markings and pavement-marking removal methods, suggesting a wide range of DOT experiences. • e availability of DOT performance evaluations of temporary pavement markings and pavement-marking removal methods is very limited, and these evaluations are oen not documented. Innovative Approaches to Temporary Pavement Markings and Pavement Marking Removal • DOTs are evaluating and implementing various strategies in an eort to improve temporary pavement markings in work zones, including special color markings, wet reective markings, enhanced tape, lead and lag markings for lane shis, foil-backed tape, abbreviated patterns for short-term markings, and a performance specication 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 inter- mediate pavement layers, using temporary tape on the wearing course, and placing permanent markings in the same location as the temporary markings. • While chemical removal methods have performed well in a research setting, they have not been implemented by DOTs, possibly because of lack of contractor expertise and imple- mentation considerations such as speed of removal and environmental concerns. Suggestions for Future Research is synthesis has identied some gaps in existing knowledge and future research needs to enhance practices for temporary pavement markings and pavement-marking removal methods in the United States. Suggestions for future research include • Research to develop new materials for temporary pavement markings, such as materials for wet weather markings and thin-surface treatments (e.g., chip seal, cape seal, and micro- surfacing) and special color markings, may enhance temporary pavement-marking perfor- mance for various conditions and surfaces. • Creation of a guidance document regarding the circumstances suitable for dierent 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 eld evaluations of temporary pavement markings and pavement-marking removal methods may help expand knowledge regarding their performance under dierent conditions.

96 Temporary Pavement Markings Placement and Removal Practices in Work Zones • Advancement of more uniform standards and specifications for temporary pavement mark- ings and pavement marking removal may encourage greater consistency between DOTs, especially with respect to provisions for CAVs. • Development of 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.