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

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65   is chapter presents case examples of temporary pavement markings and pavement marking removal for seven DOTs (Figure 53): Colorado, Florida, Illinois, Michigan, Missouri, North Carolina, and Oregon. In consultation with the topic panel, the following criteria were considered as bases for choosing the DOTs: • Diversity with respect to pavement type, climates, pavement marking types, and facility types; • Use of innovative approaches to placement, maintenance, and removal of work-zone pave- ment markings; • Level of detail provided in the survey comments; • Some preference given for DOTs with topic panel members; and • Willingness to participate in a case example (16 DOTs). Table 22 lists the DOTs selected for the case examples along with their typical materials for temporary pavement markings, typical methods to remove or cover existing pavement markings, and basis for selection as a case example. e case examples were developed based on phone interviews with personnel from the seven DOTs. Some of the topics for temporary pavement markings and pavement marking removal discussed during the interviews include the following: • General approach and experience; • Polices and standards; • Performance; • Considerations for CAVs; • Perceptions of gaps in existing knowledge; • Interest in practices of other DOTs; • Requirements for TTC, inspection, and material quality; • Challenges faced and strategies to overcome those challenges; and • Project examples. e case examples are described in the following sections of this chapter. Colorado Colorado Experience with Temporary Pavement Markings Pavement by type in Colorado is approximately 91% asphalt and 9% concrete. For temporary pavement markings, Colorado typically applies epoxy for durability so that multiple applica- tions of the markings are not required. A modied epoxy material with a shorter cure time of 20 to 30 minutes is used. In some cases, dierent types of paints, including waterborne, low VOC, C H A P T E R 4 Case Examples

66 Temporary Pavement Markings Placement and Removal Practices in Work Zones or high build, are used for temporary markings in work zones. Tabs are sometimes applied on chip seals, but Colorado nds that they do not stay on very well. Maintenance crews sometimes use tabs or light paint. Colorado generally follows the MUTCD (FHWA 2009) for temporary pavement markings, although its state supplement to the MUTCD allows for the use of a uorescent yellow-green background for markings with the word “SCHOOL” (Colorado DOT 2018b). Colorado allows for the optional use of 6-in. markings for work zones in an eort to improve visibility, especially at nighttime. Region 1 of Colorado DOT is working toward greater use of the 6-in. temporary markings in work zones as it believes the wider marking provides safety improvements at low cost. e 6-in. markings are being used on a project to rehabilitate the pavement and add an express lane on an 18-mi section of I-25 between Castle Rock and Monument (Figure 54) (Colorado DOT n.d.b.). Colorado’s standard specications require that full compliance markings be placed within 2 weeks of nal surfacing (1 week for seal coat projects) or when pavement work is discontinued for more than 2 weeks (Colorado DOT 2019b). TTC for placement of temporary pavement markings usually follows the typical application for mobile operations as shown in Standard Plan Number S-630-1 (Colorado DOT 2019c). Although Colorado has given some thought to CAVs, it does not directly incorporate them into the design process for temporary pavement markings in work zones. Colorado’s inspection process for temporary pavement markings is the same as its process for permanent markings. Various factors such as bead loading, thickness, volumetrics, and coverage Map created with mapchart.net© State selected for case example State not selected for case example Figure 53. Map showing DOTs selected for case examples.

Case Examples 67   State Basis for Selection as Case Example Typical Temporary Markings Typical Removal/Cover Methods Colorado • Western climate • 91% asphalt pavement • Developing process guide for pavement markings • Expressed interest in topic through survey Modified epoxy Water blasting, grinding Florida • Southeastern climate • 97% asphalt pavement • Representation on topic panel Paint Water blasting, grinding Illinois • Midwestern climate • 30% concrete pavement • 20% chip seal, cape seal, and microseal • Use of abbreviated marking patterns • Representation on topic panel Paint, temporary tape, durable markings Water blasting, grinding Michigan • Northern climate • Approximately 92% asphalt pavement (FHWA 2015) • Use of wet reflective markings • Use of lead and lag markings for lane shifts • Use of updated temporary tape Paint, temporary tape Water blasting, grinding, foil- backed tape (leveling or base course) Missouri • Midwestern climate • 80% asphalt pavement • Use of tabs Tabs, paint Water blasting, shot blasting North Carolina • Mid-Atlantic climate • 90% asphalt pavement • Use of performance specification for temporary markings • Use of pattern masking Paint, performance markings (durable markings) Pattern masking, grinding, water blasting Oregon • Northwestern climate • 90% asphalt pavement • Use of various types of temporary pavement markings and various methods of pavement marking removal Paint, temporary tape, buttons, tabs Grinding, sandblasting, shot blasting, water blasting, milling, black tape Table 22. Overview of case examples. Courtesy of Colorado DOT Figure 54. Temporary 6-in. pavement markings in work zone on I-25 South Gap project.

68 Temporary Pavement Markings Placement and Removal Practices in Work Zones are assessed for compliance with standards. For retroreectivity, the modied epoxy markings must meet the same minimum requirements as permanent markings, and a pay factor is applied if the minimum threshold is not met (Table  23) (Colorado DOT 2019b). Retroreectivity requirements for temporary paint markings can be added to the contract through use of a special provision, with threshold values lower than those for permanent markings. Colorado strives to improve awareness of temporary pavement markings so that it becomes more of an active consideration during design and construction. e DOT provides training classes and is currently developing a process guide for both temporary and permanent markings. is guide will provide direction on procedures, inspection processes, and selection of marking type. Colorado would like to learn about other DOT practices for temporary marking width and retroreectivity requirements and is interested in possibly exploring the use of orange markings in work zones. Colorado Experience with Pavement Marking Removal For removal of temporary pavement markings, Colorado normally uses water blasting and grinding. Water blasting is the preferred method for transition markings to limit the eects of ghost markings, but the scheduling of water blasting equipment is sometimes a challenge. Grinding is oen applied when the marking removal is in the same location as the permanent markings. Colorado’s standard specications require the contractor to propose a method of pavement marking removal at the preconstruction conference subject to approval of the engineer (Colorado DOT 2019b). Colorado’s standard specications prescribe that the extent of removal of pavement markings should be as much as possible (Colorado DOT 2019b). In addition, a wider swath of removal is necessary for transition markings as shown in Table 24. e purpose of the wider swath is to Color Retroreflectivity Reading (R) in a 1-mi Section (mcd/m2/lx) Pay Factor (%) for the Entire 1-mi Section White R 400 100 375 R < 400 85 350 R < 375 75 325 R < 350 60 300 R < 325 50 R < 300 Remove and replace Yellow R 250 100 225 R < 250 85 200 R < 225 75 175 R < 200 60 150 R < 175 50 R < 150 Remove and replace Source: Colorado DOT 2019b. Table 23. Colorado pay factors for retroreectivity of modied epoxy markings.

Case Examples 69   enlarge the removal so that it is not recognizable to drivers as a standard marking. In general, Colorado nds that removal of pavement markings works well with proper inspector enforce- ment. In Colorado’s experience, ghost markings present the greatest challenge to pavement marking removal, and Colorado is interested in learning about strategies used by other DOTs to address them. Colorado Project Example: Central 70 e Central 70 project, located on a 10-mi section of I-70 in Denver, includes pavement reconstruction, adding a new express lane in each direction, a partial lowering of the highway, and construction of a 4-acre park over the lowered section (Colorado DOT n.d.a.). e cor- ridor has high trac volumes and provides access to Denver International Airport. e total estimated construction cost is $1.2 billion, and the project is scheduled for completion in 2022. Originally, modied epoxy was solely specied for the temporary pavement markings on the project. However, it was later determined that temporary pavement markings were needed in December. To meet project schedule requirements, the DOT decided to use low-VOC paint during winter since it works well for cold weather conditions. e low-VOC paint was reapplied weekly to ensure that the markings were visible, and the pay quantities were adjusted. An aerial view of the Central 70 work zone is shown in Figure 55. Florida Florida Experience with Temporary Pavement Markings Florida’s pavement consists of approximately 97% asphalt and only 3% concrete. Florida typically uses paint for temporary pavement markings in work zones. In rare instances, thermo- plastic or temporary tape may be used. Temporary tape is not used on asphalt because Florida Width of Pavement Marking to Be Removed Width of Swath 12 in. > 8 in. 15 in. Source: Colorado DOT 2019b. < 8 in. or = 8 in. Table 24. Swath widths for transition marking removal in Colorado. Source: Colorado DOT 2019a Figure 55. Aerial view of Central 70 work zone at Peoria Street in January 2019 in Denver, Colorado.

70 Temporary Pavement Markings Placement and Removal Practices in Work Zones nds it dicult to remove aer exposure to trac. In Florida’s experience, the use of paint on concrete pavement can lead to ghost markings, so multiple applications of temporary tape are sometimes placed on concrete pavement. A pavement marking material selection chart in Florida’s design manual species the use of paint for temporary pavement markings (Florida DOT 2019). Florida is generally satised with the performance of paint for temporary pavement markings, although sometimes designers do not specify multiple applications for long work zones, which can lead to issues with accurate payment to contractors. Florida adopted the national MUTCD and follows the MUTCD standards for temporary pavement markings in work zones (FHWA 2009). e DOT uses a 6-in. width for temporary markings. Temporary paint markings in work zones must meet the requirements for permanent pavement markings for standard paint (Florida DOT 2020b). For sections greater than 500 feet in length, removable tape must be installed within a length tolerance of 2% using a mechanical applicator. Removable tape may be placed by hand on sections with a length of 500 feet or less. e minimum retroreectivity values for standard paint and removable tape shown in Table 25 must be met for temporary pavement markings in work zones. In addition, black masking tapes and black parts of contrast tapes are required to be nonreective with a reectance lower than 5 mcd/m2/lx. e contractor must measure, record, and certify the retroreectivity values for standard paint, and Florida DOT may test the retroreectivity markings within 3 days of receiving the certication. Standard paint markings with retroreectivity values falling below 150 mcd/m2/lx within 6 months must be replaced at the contractor’s expense. Florida maintains a pavement marking database that provides information regarding retroreectivity and historical data for permanent pavement markings. Florida’s standard drawings provide layouts for pavement markings and other channelizing devices for various scenarios and typical applications for the application of temporary pavement markings (Florida DOT 2020a). Moving forward, Florida is beginning to consider design aspects for CAVs for temporary pavement markings in work zones. e DOT would like to see more research undertaken for wet recovery and wet weather for temporary markings and is interested in learning about the general practices of other DOTs with respect to temporary pavement markings. Florida Experience with Pavement Marking Removal For removal of pavement markings, Florida normally uses water blasting or grinding. Shot blasting is also sometimes used, but there is only one contractor in the state who performs this method. e Florida Turnpike usually applies a mill and ll to the nal surface as a result of high speeds and trac volumes. Florida investigated the potential use of chemical removal methods but was not able to nd a contractor who could perform the work. Florida’s standard specications allow for the use of any removal method that completely removes the existing pavement markings without damaging the pavement surface or texture (Florida DOT 2020b). Temporary Marking Color Time After Initial Placement (Months) Minimum Retroreflectivity (mcd/m2/lx) White 0 300 Yellow 0 250 White 6 150 Yellow 6 150 Source: Florida DOT 2020b. Table 25. Retroreectivity requirements for standard paint and removable tape in Florida.

Case Examples 71   e use of black paint or fog seal to cover existing pavement markings is not permitted (Florida DOT 2020a). With regard to performance, Florida nds that the water blasting is expensive, and there is variability in the quality of the water blasting equipment. An example of blasting equipment used in Florida is shown in Figure 56. e DOT also experiences dierences in the quality of the grinding removal based on the operator. Ghost markings are a major concern, especially for larger work zones. Florida nds the eradication of markings on multiple lane shis to be particu- larly challenging. Florida would like to see additional research on eld testing of ghost markings and is interested in learning about the practices of other DOTs to address ghost markings. Florida Project Example: I-75 Off-Ramp at SH-70 (Manatee County, Florida) e intersection of the I-75 o-ramp and SH-70 in Manatee County, Florida, underwent a full reconstruction in 2020. is intersection experiences heavy trac with high trac volumes on SH-70 and has several trac control phases. Waterborne paint is being used for the temporary pavement markings. Frequent visual assessments of the pavement markings by Florida DOT inspection sta are required at this intersection because of signicant problems with ghost markings. Although the existing pavement is asphalt, it looks very white to the naked eye because of aging and the dierent types of aggregate used in the pavement. Aer removing the existing pavement mark- ings, the new white and yellow pavement markings are dicult to see during both daytime and nighttime (Figure 57). Frequent turning movements contribute to rapid deterioration of the pavement markings, which need to be refurbished every 4 to 6 months. Florida installed many RPMs on each trac stripe to help guide drivers at night. Illinois Illinois Experience with Temporary Pavement Markings Illinois typically installs temporary tape and paint for temporary pavement markings in work zones on asphalt and paint for temporary pavement markings in work zones on concrete pavement. Durable marking materials such as urethane, polyurea, and epoxy are sometimes Courtesy of Hog Tech Technologies Figure 56. Example of water blasting equipment used in Florida.

72 Temporary Pavement Markings Placement and Removal Practices in Work Zones used for temporary applications with high volumes or long durations (Illinois DOT 2015). Contrast markings are occasionally applied on concrete pavements. e use of temporary wet reective markings is only allowed for a research project to assess the durability of wet reective marking materials (Illinois DOT 2015). Local agencies sometimes use low-cost tape. e designer typically species the type of temporary pavement marking to be applied on a given project. Illinois has a high percentage of concrete pavement. e percentage of roadways by pavement surface type in Illinois is as follows: 50% asphalt, 30% concrete, and 20% thin surface treatments (chip seal, cape seal, and microsurfacing). While Illinois has its own supplement to the MUTCD (Illinois DOT 2014), guidance for short-term pavement markings may be found in its Policy Document TRA-17 (Illinois DOT 1990). is policy species that short-term markings consisting of abbreviated patterns are required at the end of each day for all lanes open to trac. For the short-term markings, yellow and white stripes with a length of 4 feet and spacing of 40 feet are applied for centerline and lane line markings, respectively. For edge line delineation, diagonal stripes with a width of 4 in. and length of 2 feet may be applied on the shoulders at intervals of 50 feet on ramps and 200 feet on mainlines. Roadways with ADT values and truck volumes lower than the values shown in Table 26 are exempt from the policy requirements for short-term pavement markings. According to the Illinois Standard Specications, the short-term markings should be replaced with standard temporary or permanent pavement markings within 3 calendar days for no-passing zones and 14 calendar days for all other markings (Illinois DOT 2016a). Layouts for temporary pavement markings, signs, and other channelizing devices for various scenarios are shown in the Illinois standard drawings (Illinois DOT 2019). Markings are typically placed using mobile operations. Temporary marking materials must meet the requirements of Standard Specication Sections 1095.02 (Paint Pavement Markings) and 1095.06 (Pavement Marking Tape) (Illinois DOT 2016a). Minimum daylight reectance requirements are 85% for white paint and 50% for yellow paint. Temporary tape is classied as Type I or Type III, with Type III tape having a higher durability based on Federal Test Method Standard No. 141A, Method 6192. For temporary tape, Courtesy of Florida DOT Figure 57. Pavement markings and ghost markings in work zone at I-75 off-ramp and SH-70 in Manatee County, Florida. ADT Multiunit trucks 2,500 10% 2,000 15% 1,500 20% 1,000 25% Source: Illinois DOT 1990. Table 26. Threshold volumes for low- volume roads exempt from short-term markings policy in Illinois.

Case Examples 73   minimum requirements for the coecient of retroreected luminance (RL) using ASTM D4061 are shown in Table 27. Temporary markings are reviewed visually by the resident engineer or inspector at intervals of 1 to 2 weeks, depending on the size of the project. e Illinois eld manual for trac control (Illinois DOT 2016c) includes evaluation guidance for work-zone pavement markings, which is consistent with ATSSA’s Quality Guidelines for Temporary Trac Control Devices and Features (ATSSA 2017). Illinois nds that the temporary pavement markings generally do not perform well. In the DOT’s experience, paint wears out quickly, and low-cost tape does not hold up. Illinois’ greatest challenge involves nding suitable temporary pavement markings for thin surface treatments on asphalt pavement such as chip seal, cape seal, and microsurfacing. Illinois nds that tape does not adhere well to these surface treatments, and paint disappears because the emulsion bleeds. For these surface treatments, Illinois typically uses TRPMs with covers, and the cover is removed when the treatment is applied. Other hurdles faced by Illinois in the use of temporary pavement markings include getting the temporary markings to stay down and matching trac volumes to the appropriate type of temporary pavement marking. Illinois gives some thought to future accommodation of CAVs, but currently does not consider them in the design process. Illinois is interested in possibly exploring the use of hot spray thermoplastic for temporary pavement markings and in learning more about the experiences of other DOTs with respect to selection of temporary marking type for dierent surfaces and performance of temporary pavement markings. Illinois Experience with Pavement Marking Removal Methods for pavement marking removal that are employed in Illinois include grinding, water blasting, black tape, and burning. On intermediate layers of asphalt pavement, an eort is made to set up construction phasing that allows the temporary markings to be paved over with the next layer. In most instances, the contractor selects the preferred method for marking removal, although sometimes the engineer may make the decision. According to the Illinois standard specications, the contractor may use any method that does not cause material damage to the pavement surface (Illinois DOT 2016a). e contractor must clean debris from the pavement using compressed air or water blast. e Illinois eld manual for trac control provides quality guidelines and ratings criteria for the removal of conicting pavement markings, as shown in Table 28 (Illinois DOT 2016c). e manual includes example pictures to depict the dierent ratings. e Illinois specications also include time and equipment requirements for pavement marking removal. e engineer is required to approve grinding equipment. Existing conicting Coefficient of Retroreflected Luminance (RL)—mcd/ft2/footcandle (mcd/m2/lx) Type I Type III Observation Angle White Yellow Observation Angle White Yellow 0.2° 2,700 2,400 0.2° 1,300 1,200 0.5° 2,250 2,000 0.5° 1,100 1,000 NOTE: 1 mcd/ft2/footcandle = 1 mcd/m2/lx. Source: Illinois DOT 2016a. Table 27. Minimum values for coefcient of retroreected luminance (RL) for temporary tape markings in Illinois standard specications.

74 Temporary Pavement Markings Placement and Removal Practices in Work Zones markings must be immediately removed. In addition, all temporary markings must be removed within 5 days of the placement of permanent markings. Illinois nds ghost markings to be a major concern for the removal of pavement markings. e DOT is seeking a good solution to the problem of ghost markings. Another concern is that black tape is sometimes mistaken for permanent markings by drivers. Illinois Project Example: TRPM on Seal Coat An unmarked but state-maintained route required the application of seal coat on a 2-mi section. For seal coats and other thin surface treatments, the Illinois recurring special provi- sions (Check Sheet No. 32) mandate that TRPMs be placed at 4- spacing every 40 feet for a skip dash and 5- spacing for centerlines (Illinois DOT 2016b). Example TRPM layouts for the project are shown in Figure 58. As described previously, the TRPMs include a plastic cover that is removed aer the application of the thin surface treatment to expose the reective tab. While Illinois nds that this system is relatively eective for short-term markings on thin surface Rating Criteria for Removal of Conflicting Pavement Markings Acceptable • Removal of all conflicting markings • Removal performed in accordance with the applicable traffic control standard, the standard specifications, and the traffic control plan • Removal meets the satisfaction of the engineer Marginal • Presence of at most 10% of conflicting markings after removal • Presence of at most 10% of any individual conflicting line after removal Unacceptable • Presence of more than 10% of conflicting markings after removal • Presence of conflicting letters or symbols • Presence of more than 10% of any conflicting line after removal • Presence of lines or markings outside of the new traveled way with the potential to cause confusion Source: Illinois DOT 2016c. Table 28. Illinois quality guidelines for pavement marking removal. Courtesy of Illinois DOT Figure 58. Example TRPM layout on seal coat project in Illinois in (a) daytime and (b) nighttime.

Case Examples 75   treatments, it is seeking alternative solutions because of the high cost ($4,000 to $7,000 per mi) of these markings. However, Illinois has not been able to nd a suitable alternative because the use of pavement marking tape or liquid markings is not allowed within 10 days of application of the surface treatment, during which time water is released. Michigan Michigan Experience with Temporary Pavement Markings Michigan typically uses paint and temporary tape for temporary pavement markings in work zones. For leveling or base courses, foil-backed tape that melts into surface is sometimes applied. Tabs may be installed as directed by the engineer to supplement the temporary markings on tangents, trac transitions, runarounds, and crossovers (Michigan DOT 2012). Spray thermoplastic and tabs are typically used for microsurfacing and chip seals, respectively. Contrast markings may be applied to concrete pavement (Michigan DOT 2020c). e selection of marking type is typically determined by the designer based on pavement type and construc- tability. Concrete pavement accounts for approximately 8% of the pavement in Michigan based on Highway Performance Monitoring System (HPMS) data (FHWA 2015). e pay items for temporary markings are designated as Type R (removable tape) or Type NR (nonremovable tape or paint) in Michigan’s standard specications (Michigan DOT 2012). Type R markings are required on the nished pavement surface when temporary markings are not in the same location as permanent markings or as designated by the engineer. Type NR markings are used when the temporary markings are in the same location as permanent mark- ings or when the pavement surface will be removed or replaced during construction. In addition, Type NR markings are required when temporary markings are placed between November 1 and April 15 or when temporary markings are removed aer December 1. Michigan is known to be the rst state to require all of its temporary markings to be wet reective and has implemented improvements to marking materials, including the use of wet reective optics and enhanced tape. e wet reective markings include both paint and tape (Michigan DOT 2020c). Temporary Type R tape and Type NR paint are required to be wet reective. Specications for the wet reective markings are provided in a frequently used special provision (Michigan DOT 2020a). Initial retroreectivity requirements for temporary wet reective Type NR markings are shown in Table 29. e wet reective paint is placed at a thickness of 18 mils at a maximum speed of 8 mph. Michigan nds that the wet reective markings work well and help increase visibility of the temporary markings, especially at night in the rain (Figure 59). Michigan is in the process of evaluating enhanced tape materials for temporary pavement markings. e goal of this evaluation is to improve durability and facilitate faster removal with Temporary Wet Reflective Type NR Pavement Markings Average initial retroreflectivity at 30-m geometry in mcd/m2/lx with flow of placement Test Method Color White Yellow Dry (ASTM E1710) 700 500 Wet Recovery (ASTM E2177) 250 200 Source: Michigan DOT 2020a. Table 29. Michigan retroreectivity requirements for temporary wet reective Type NR pavement markings.

76 Temporary Pavement Markings Placement and Removal Practices in Work Zones the intention of reducing worker exposure to trac. e improved tape was tested on three projects in 2019, and it will be used on all Interstate projects in 2020. While Michigan has its own state MUTCD (Michigan DOT 2011), it generally follows the FHWA MUTCD (FHWA 2009) with respect to temporary pavement markings. Michigan provides additional guidance for temporary pavement markings in its Work Zone Safety and Mobility Manual (Michigan DOT 2020c). Temporary broken centerline markings consist of 4- dashes at 50- spacing, and solid edge lines are used. Grabber cones or drums may be used in lieu of edge lines to delineate the shoulder for durations between 3  days and 14 days. Michigan is switching to 6-in. markings (12 in. for gore markings) in 2021. Lead and lag markings (300  for freeways and 150  for nonfreeways) are used before and aer lane shis to help make the shis more visible in sun glare. Temporary route shields made from preformed thermoplastic are sometimes used to help guide drivers through the work zone (Figure 60). Inspectors are required to visually evaluate the temporary pavement markings Courtesy of Michigan DOT Figure 59. Michigan work zone during wet nighttime conditions, with wet reective paint on the left side of the roadway. Existing markings that are not wet reective paint are used on the right side of the roadway. Courtesy of Michigan DOT Figure 60. Example temporary route shield marking in Michigan work zone.

Case Examples 77   daily, and Michigan typically uses its pavement marking convoy typical application (Michigan DOT 2020d) for temporary markings. Challenges experienced by Michigan during the placement of temporary markings include weather limitations, the need for greater awareness of temporary markings by contractors, and enforcement of the contract provisions with respect to temporary markings. Michigan is exploring the feasibility of performing trac switches with rolling closures and slower freeway trac speeds to limit worker exposure and improve safety. Michigan believes there is a need for greater consistency between states in the placement of temporary pavement markings, especially with regard to considerations for CAVs. Michigan Experience with Pavement Marking Removal For pavement marking removal, Michigan typically uses grinding on asphalt pavement and water blasting on concrete pavement. For removal of less than 5,000  of pavement markings per stage, Michigan’s standard specications allow the use of the following methods: sand- blasting, shot blasting, high-pressure water, steam or superheated water, or mechanical devices (e.g., grinders, sanders, scrapers, scariers, and wire brushes) (Michigan DOT 2012). For removing more than 5,000  of pavement markings per stage, self-propelled truck-mounted removal equipment is mandated. Wet reective Type NR paint must be removed by the least abrasive method at the direction of the engineer (Michigan DOT 2020a). Water blasting is not allowed on asphalt pavement because Michigan has found that it can remove some of the nes. e use of paint or bituminous bond coat to cover existing markings is prohibited (Michigan DOT 2012). e method of pavement marking removal must be approved by the engineer, and the contractor is required to minimize the damage to the pavement surface texture when removing pavement markings. Markings that are not applicable must be removed before any changes in trac patterns with a duration of more than 3 days (Michigan DOT 2020c). Michigan nds ghost markings to be a signicant concern. e state has not yet found a good solution to the problem and is interested in learning about possible solutions tried by other states. Michigan would like to improve the removability of pavement markings, thus reducing worker exposure. Michigan also nds it challenging to ensure that paint removal is performed properly and inspected. Michigan Project Example: Pilot Testing of Improved Tape Materials In 2019, Michigan tested enhanced tape materials to improve durability and removability (Michigan DOT 2020b). e evaluations were performed at three locations on I-75 and I-94. e wet reectivity and adhesive of the tapes were the same as the prior tapes. e dierent tapes installed under ideal weather conditions performed well. At the location on I-75 near SH-75, the process for removing the test tape was found to be four times faster than the old tape. In addition, the old tape frequently broke and frayed during the removal process. A visual comparison of the pulling of the old tape and test tape can be seen in Figure 61. Overall, Michigan found that the test tapes were more durable and easier to remove than the old tape materials. Missouri Missouri Experience with Temporary Pavement Markings Missouri’s pavement consists of approximately 80% asphalt and 20% concrete. Missouri mostly uses temporary tabs for temporary pavement markings in work zones because of ease of placement. Temporary paint is sometimes applied in work zones with longer durations. Tape

78 Temporary Pavement Markings Placement and Removal Practices in Work Zones is rarely used, although it is occasionally specied for lane shis. Missouri standards do not allow for the application of temporary tape on the nal surface unless specied in the plans (Missouri DOT 2019b). Missouri uses a 6-in. width for temporary tabs in work zones and a 4-in. width for other types of temporary pavement markings in work zones. Tabs are placed at 40- intervals (Figure 62). Example eld applications of tabs are shown in Figure 63. Temporary paint must meet the retroreectivity requirements shown in Table 30. Construction inspec- tors review the temporary markings in the work zone, and a handheld retroreectometer is sometimes used. Missouri incorporates Section 6F of the MUTCD (FHWA 2009) into Section 616.6 (Tempo- rary Trac Control Zone Devices) of its Engineering Policy Guide (EPG) (Missouri DOT 2019a). Courtesy of Michigan DOT Figure 61. Comparison of pulling tape in Michigan: (a) old tape and (b) test tape with improved durability and removability. Source: Missouri DOT 2019b Figure 62. Example tab layout from Missouri Standard Drawing 620.10G.

Case Examples 79   e use of temporary pavement markings on the nal pavement surface is limited to 14 days aer the application of the nal pavement surface treatment (Missouri DOT 2019a). A job special provision can be added to the contract to limit the length of paving that triggers the 14-day time limitation for temporary markings. is job special provision requires temporary striping to be applied if permanent markings are not in place by October 1, with the permanent marking being installed in the spring. Temporary markings are required to be placed to rep- resent any permanent marking a roadway displays. All routes in Missouri receive a centerline marking, and edge line markings are based on ADT. Routes with an ADT greater than 400 vpd and a width of at least 20  have both a centerline and edge line markings. Routes with an ADT less than 400 vpd and a width of at least 18  typically only have a centerline. Typical applications for moving operations are used for TTC in placement of the temporary markings or marking removal. Missouri also has a specication that requires temporary markers to be removed and collected to keep plastics out of the environment. Missouri currently does not consider CAVs in the process of selecting temporary pavement markings but believes that it may have to reexamine the use of tabs (which cannot provide guidance to CAVs with the current image- processing technology) in the future if CAVs become more prevalent. Missouri encounters many challenges in its application of temporary pavement mark- ings. In Missouri’s experience, temporary tabs do not stay down well if they are not installed Courtesy of Missouri DOT Figure 63. Example tab applications in Missouri work zones: (a) rural two-lane highway; (b) Interstate. White (mcd/m2/lx) Yellow (mcd/m2/lx) % Payment 275a 200a 100% > or = 200b > or = 175b Maintain Source: Missouri DOT 2019c. aMinimum requirement for initial application of temporary paint. bTemporary paint shall be maintained to this level at the ’ Table 30. Minimum retroreectivity requirements for temporary paint in Missouri standard specications.

80 Temporary Pavement Markings Placement and Removal Practices in Work Zones according to the manufacturer’s recommendations or they are in place longer than 14 days. Missouri finds that tabs are also susceptible to damage from construction equipment, such as rollers and asphalt trucks, during paving operations. These issues result in the need to replace damaged tabs, which increases the exposure of workers. In an evaluation study of tabs placed on a short section of US-63 in Missouri with no construction equipment, the tabs lasted over 2 weeks. Missouri finds that tabs or paint do not stay down well on chip seals. Temporary paint often requires two to three good applications. A shortage of striping contractors limits the use of temporary paint. Missouri once used both temporary tabs and temporary raised markers in combination but moved away from the raised marker design to permit easier removal of the temporary markings. Too many times raised markers would be rolled into the surface by the paving operations, making their removal impossible. Missouri would like to learn more about the practices and experiences of other DOTs for temporary markings with respect to types of materials, performance of tabs, procedures for tracking the 14-day time limit, and enforcement of contract provisions for temporary pavement markings. Missouri Experience with Pavement Marking Removal For pavement marking removal, Missouri normally uses water blasting on asphalt and shot blasting on concrete. Grinding is also sometimes used, but water blasting is preferred because of concerns about scarring of pavement from grinding, especially on lane shifts. In some cases, the resident engineer or inspector may not allow grinding. Missouri’s standard specifications require the removal of at least 95% of the existing marking, and the contractor is responsible for the repair of any excess damage or scarring to the pavement (Missouri DOT 2019c). Challenges faced by Missouri with respect to pavement removal include ghost markings and performance issues. Ghost markings present a major challenge to Missouri’s practices for pavement marking removal. Marking removal on poor pavement surfaces sometimes leads to deterioration of the pavement as a result of the loss of asphalt and aggregate. Missouri experiences other performance issues with pavement marking removal. Water blasting can sometimes blow apart asphalt pavement and damage joint sealant on concrete pavement. Missouri finds that shot blasting works well on concrete pavement but is expensive. Because of these concerns about existing removal methods, Missouri believes there is a need to develop innova- tive pavement-marking removal methods that do not disturb the pavement. Missouri Project Example: I-270 North Project in Saint Louis (Design–Build) A design–build project for infrastructure improvements on a 14.5-mi section of I-270 on the north side of Saint Louis, Missouri, is under construction with an anticipated completion date of December 1, 2023. The scope of the project includes interchange improvements, bridge replacements, new bicycle and pedestrian crossings over I-270, a new counterflow bus lane, addition of a fourth lane on I-270, conversion of adjacent streets to continuous one-way outer roads, and a 2-in. mill and overlay of the I-270 pavement (Missouri DOT 2020). During the procurement phase, the contractor had the option to propose use of different standards. While the contractor requested the use of 15 alternative standards, none of these standards were related to temporary pavement markings in the work zone. Thus, the Missouri DOT specifications and standards for temporary pavement markings are being followed. While the project is in the early stages of construction, the contractor anticipates that paint will predominantly be used for temporary pavement markings along with some temporary tape. An example of the paint for temporary pavement markings in the I-270 work zone is shown in Figure 64. For removal of pavement markings, water blasting or grinding will be used based on pavement type.

Case Examples 81   Missouri Project Example: I-44 in Saint Louis (Ghost Markings) Bridge work and pavement resurfacing have been performed in phases on the I-44 corridor in Saint Louis, Missouri, from 2015 to 2021. e corridor experiences heavy trac, with AADT of approximately 98,000 vpd and 12% trucks in 2015 (Missouri DOT 2015). e rst phase of the project from the Saint Louis city line to South Kingshighway Boulevard included the rehabilita- tion of four bridges. e initial trac pattern during construction included three 10- lanes with a Jersey barrier. e corridor experienced heavy trac in the work zone, and the DOT decided to change the trac pattern to three 11- lanes eastbound and two 12- lanes westbound. Aer the change was made to the three 11- eastbound lanes and two 12- westbound lanes, the ghost markings from the previous 10- lanes and original 12- lanes led to some driver confusion, especially with sun glare from the sunrise in the morning peak period. To address this concern, the temporary striping for the three 11- eastbound lanes and two 12- westbound lanes was changed from intermittent to a solid line to make the markings more visible to drivers. Example photographs of the I-44 ghost markings are shown in Figure 65. e later stages of construction Courtesy of Missouri DOT Figure 64. Example of temporary pavement markings (paint) in work zone on I-270 near Old Halls Ferry Road. Courtesy of Missouri DOT Figure 65. Ghost markings in work zones on I-44 in Saint Louis, Missouri: (a) four 12-ft lanes (I-44 eastbound, daytime, May 2020); (b) lane reduction from four 12-ft lanes to three 10-ft lanes (I-44 westbound, nighttime, March 2016); and (c) lane reduction from four 12-ft lanes to three 10-ft lanes (I-44 eastbound, sunrise, March 2016).

82 Temporary Pavement Markings Placement and Removal Practices in Work Zones included a 4-in. mill and ll, so the ghost markings were eradicated when the project was completed (Figure 66). North Carolina North Carolina Experience with Temporary Pavement Markings North Carolina typically uses standard water-based paint for temporary pavement markings on non-Interstates and nonfreeway work zones. North Carolina primarily uses asphalt on its Interstate/freeway network with concrete pavement representing approximately 10% of its mileage. In the past, North Carolina did not require any dierent type of pavement marking systems for its high-volume Interstates and freeways than for its secondary system. Now, the DOT has developed specications that require “semidurable,” highly reective pavement markings in work zones on Interstates and freeways. For Interstate and freeway projects, North Carolina developed and implemented a perfor- mance specication for work-zone pavement markings that allows the contractor to choose between thermoplastic (50 mil), polyurea, epoxy, polymer paint, or temporary tape (Figure 67). e liquid paint systems all require 20 mil applications. Factors aecting the choice of temporary pavement marking include the pavement type, cost of material, duration of the trac pattern, and the frequency of snowplowing. As part of the performance specication, retroreectivity minimums are required. Measurements are taken with a mobile retroreectometer, and the results are compared with threshold values (Table 31). e retroreectivity measurements are taken within 30 days of placement, and North Carolina reserves the right to take retroreectivity measurements at any subsequent time. North Carolina has experienced varying degrees of success with the performance speci- cation. While there have not been any debonding failures, it has sometimes been dicult to achieve the required retroreectivity values, especially on older pavements. In addition, North Carolina nds it challenging to strike a balance between giving the contractor exibility while being somewhat prescriptive and providing contractor guidance. Overall, North Carolina Image capture: May 2019; © 2020 Google Figure 66. I-44 eastbound near Southwest Avenue interchange in Saint Louis, Missouri.

Case Examples 83   believes that use of the specication has led to a signicant improvement in the quality of its temporary pavement markings on Interstates and freeways. Although North Carolina has its required statewide specications (North Carolina 2018a), it follows the MUTCD standards (FHWA 2009) with respect to temporary pavement markings. A marking width of 6 in. is typically used, while 4-in. markings are oen applied on secondary or urban roads with narrower lane widths. North Carolina’s standard specications require daily inspection of TTC devices (North Carolina DOT 2018a). e DOT’s performance pavement marking specication ensures that both daytime “presence” and retroreectivity for nightly performance are achieved for the duration of the trac pattern. e key compliance feature is the statewide mobile scanning contract. All trac pattern changes on Interstates and free- ways are scanned within 30 days of the pattern change, and the data are submitted to the resident engineer and to the statewide work zone engineer. However, North Carolina is interested in learning more about the practices of other DOTs regarding placement of markings under high speeds and trac volumes. North Carolina nds that dierent types of temporary markings are suitable for specic conditions. Polymer paint is commonly applied on short-duration activities where trac patterns are changed more frequently and snowplowing does not frequently occur. In North Carolina’s experience, thermoplastic works better where there are higher trac volumes, trac patterns with longer durations, and less frequent snowplowing. Polyurea provides better performance in areas with higher trac volumes, higher frequency of snowplowing, and trac patterns of longer durations. Source: Kite n.d. Figure 67. Example of temporary pavement markings using performance specication in work zone in North Carolina. Temporary Marking Color Time After Initial Placement (Months) Minimum Retroreflectivity (mcd/m2/lx) White 0-1 375 Yellow 0-1 250 White 6 325 Yellow 6 200 White 12 150 Yellow 12 100 Source: Kite n.d. Table 31. Minimum retroreectivity requirements for temporary pavement markings in North Carolina performance specication.

84 Temporary Pavement Markings Placement and Removal Practices in Work Zones North Carolina Experience with Pavement Marking Removal North Carolina developed and implemented a specication for pattern masking, which is a black polymer surface coating applied to the entire width of the roadway in 6- passes (Figure 68). e specication was initially developed to address pavement rutting or damage, “ghost lines,” and other nondesirable outcomes caused by the grinding of thermoplastic mark- ings on asphalt pavement (Figure 69). North Carolina later perceived a need to prepare for CAVs, which became an additional motivation for the continued development and use of pattern masking in the state. e greatest challenge experienced by North Carolina in imple- menting the pattern masking has been durability, and other challenges include dry times, winter temperatures, and the need for a large tank size for application. In the 4 years that North Carolina Source: Kite n.d. Figure 68. Example of pattern masking in work zone in North Carolina. Source: Kite n.d. Figure 69. Example of deep rutting as a result of aggressive pavement marking removal.

Case Examples 85   has been using the pattern masking, several revisions to the specification have been made to increase the thickness to reduce glare, modify the grip element to increase skid resistance and eliminate seams, and to reduce drying time, especially during cooler temperatures. To reduce contractor risk, North Carolina has offered to reimburse the contractor if there are any issues with the pattern masking material. To date, the pattern masking has been applied on approximately half of the projects for which it is specified. Material availability, weather, and value engineering sometimes preclude its use. Alternative removal methods to pattern masking include grinding on asphalt pavement and water blasting on concrete pavement. North Carolina’s standard specifications do not allow for the use of high-pressure water blasting on asphalt pavement (North Carolina DOT 2018a). Moving forward, North Carolina would like to see increased use of the pattern mask- ing, which it believes is an effective solution to the challenges posed by ghost markings and CAVs. North Carolina continues to learn from its application on specific projects and modify the specification as needed. One of the striping contractors in the state recently purchased equipment solely for the application of pattern masking, a development which is anticipated to help expand its use. Once this application becomes a standard method of work-zone pattern changes, North Carolina anticipates that more striping contractors will get involved, leading to greater acceptance as well as improving the cost-effectiveness of the application. North Carolina is interested in learning about the practices of other DOTs with regard to preparing for CAVs. North Carolina Project Example: US 17/74 in Wilmington, North Carolina (Pattern Masking) One of North Carolina’s early applications of pattern masking took place in 2014 on a 2.5-mi section US 17/74 in Wilmington, North Carolina, with four lanes and ADT of 84,000 vpd (Kite n.d.). This project was selected for pattern masking because removal of incorrectly installed pavement markings was leading to pavement damage and problems with dust control. North Carolina was interested in evaluating the durability of the pattern masking for 12 months under high traffic in a coastal environment. Since this project was an early evaluation of the pattern masking, it was applied in 2-ft widths instead of the 6-ft widths that are currently implemented. A thickness of 10 to 12 mils instead of the current 20 mils was used. Results from the pattern masking at 2 months and 12 months are shown in Figure 70. As shown in the figure, the markings were still covered after 2 months, but the application appeared to be uneven with missing gaps. After 12 months, ghost markings were visible, and the contractor covered the ghost markings with black paint. The performance markings were still visible after 12 months although they showed more wear on concrete bridge decks. As described in the previous section, North Carolina made several improvements to the pattern masking based on its implementation experience with projects such as this one. Other Pattern Masking Examples in North Carolina Based on prior experience with other projects, North Carolina made some changes to the required thickness and application widths to ensure more uniformity during application and to improve the durability of the masking material. Figure 71 shows an example of the masking and performance pavement system used for an on-site detour alignment on I-40 (Burke County) with an ADT of 40,000. In typical line removal applications, the scarred pavement resulting from traditional line removal application could possibly create driver confusion during wet night and low light conditions. North Carolina finds that by using the masking, not only are

86 Temporary Pavement Markings Placement and Removal Practices in Work Zones the old lines concealed, but no pavement rutting exists while creating the ultimate contrasting surface for the performance lines to be placed. Figure 72 shows a picture of I-40 in Wake County. To test the product’s durability, North Carolina selected this project because it had the largest trac volume of any project to date with over 180,000 ADT. e gure shows signicant contrast between the eastbound and westbound directions as a result of the pattern masking. Initially, the masking material concealed the old thermoplastic lines and create the desired contrast for the performance pavement markings (polymer paint). However, aer 120 days, the material was demonstrating excessive wear, and the DOT decided to remove the existing lines. Based on the results of this project, durability was an issue resulting in large part from the extremely high volumes. Since this time, changes have been made to improve the product’s durability as well as the ability to install in cooler temperatures. Source: Kite n.d. Figure 70. Pattern masking on US 17/74 in Wilmington, North Carolina (a) 2 months after placement and (b) 12 months after placement. Courtesy of North Carolina DOT Figure 71. Work-zone pattern masking and thermoplastic (50 mil) used on asphalt pavement on I-40 in Burke County, North Carolina (40,000 ADT).

Case Examples 87   In summary, North Carolina is learning and adjusting with each installation of the masking application. e contracting and striping industry is becoming more knowledgeable as well as acquiring equipment that can successfully and productively install the material. It is North Carolina’s belief that the masking and performance specications for temporary pavement markings will soon see more successful and consistent applications as a result of the prior experiences as well as through industry acceptance. Oregon Oregon Experience with Temporary Pavement Markings Approximately 90% of Oregon’s pavement is asphalt. Oregon uses various types of temporary pavement markings for work zones, including paint, temporary tape, buttons, and tabs. Oregon refers to buttons as reective pavement markers and tabs as exible pavement markers. e decision on which marking type to use is oen made by contractors, but sometimes the designer species the temporary marking type. Factors taken into consideration when selecting a type of temporary pavement marking include pavement type and duration. In Oregon’s experience, the various types of temporary pavement markings are suitable for dierent conditions. Tabs are typically used for chip seals. While Oregon has a state supplement (Oregon DOT 2011) to the national MUTCD (FHWA 2009), the DOT follows the standards of the MUTCD with respect to temporary pavement markings. Oregon uses a 4-in. width for its temporary pavement markings (Oregon DOT 2018). Materials meeting the requirements for permanent markings are usually applied, except that the temporary paint has fewer beads. Tabs are used to supplement or simulate Courtesy of North Carolina DOT Figure 72. Work-zone pattern masking with polymer paint used as the performance pavement marking on I-40 in Wake County, North Carolina (180,000 ADT).

88 Temporary Pavement Markings Placement and Removal Practices in Work Zones solid lines. Various layouts for tabs are shown in Oregon’s standard drawings (Figure 73) (Oregon DOT 2019b). Oregon’s standard specications require that permanent markings be placed on the nal pavement wearing course within 28 days of placement of temporary pavement markings (Oregon DOT 2018). Oregon developed its own handbook for TTC for work zones of 3 days or less which includes typical applications (Oregon DOT 2016). Inspec- tors review the markings before the roadway is opened, and unacceptable markings must be removed and replaced. Oregon’s climate poses challenges to the use of temporary markings because of a high amount of rainfall and lower temperatures. Oregon nds that the temporary paint does not last long, and it is hard to get markings to stay in place during the winter. In Oregon’s experience, temporary tape is easier to remove than paint but labor-intensive to install. Oregon also noted that buttons (reective pavement markers) last longer than paint but require signicant maintenance. Other challenges faced by Oregon related to temporary markings include maintenance of temporary markings and ensuring proper engineering application of markings. Oregon currently gives some limited consideration to CAVs in using temporary pavement markings but expects them to become more of a factor in the future. To address these and other challenges, Oregon would like to learn more about the practices of other DOTs regarding innovative types of markings, wet applications, simulated markings, use of temporary markings for work zones of short and long duration, and practices for delineat- ing shoulders. Oregon believes that developing a guidance document regarding the conditions suitable for dierent types of temporary markings would be benecial. Source: Oregon DOT 2019b Figure 73. Example layout of tabs from Oregon Standard Drawing TM810.

Case Examples 89   Oregon Experience with Pavement Marking Removal Oregon uses several methods for pavement marking removal on intermediate layers of asphalt, including grinding, sandblasting, shot blasting, water blasting, milling, and black tape. Black tape is sometimes used on nal surfaces on asphalt pavement and on concrete pavement. e contractor typically selects the method for removing pavement markings. Oregon’s standard specications include a performance specication (Section 225.43i) (Oregon DOT 2018). e use of paint or asphalt to cover existing markings is not allowed. A maximum of 1/8 in. of pavement may be removed during the process of pavement marking removal. e standard specications prohibit the use of grinding to remove existing markings from the wearing course unless the new markings match the original conguration. Oregon experiences ghosting problems with many of the pavement-marking removal methods. Several strategies are used to limit the eects of ghosting. Temporary tape or another type of marking that removes easily is frequently used on the wearing course. In addition, permanent markings are oen placed in the same location as the temporary markings. Oregon Project Example: I-5 A pavement preservation project on I-5 from Woodburn to Salem is under construction and was completed in 2020. e project includes 12.4 mi of repaving and the resurfacing of six bridges (Oregon DOT 2019a). e project was on a fast track for completion, with design undertaken in fall 2018 and project letting in spring 2019. is section of I-5 is a high-speed corridor with heavy trac volumes (approximately 85,000 to 97,000 vpd). Since the project was a pilot for a work-zone safety initiative, trac was partially run on the shoulder to increase the separation of vehicles from the work zone. Temporary pavement markings consist primarily of paint along with reectors. Markings suitable for a longer duration were preferable, as it was anticipated that the temporary markings would need to be le in place during winter until permanent markings could be applied. High speeds and heavy trac precluded the widespread use of tabs, although tabs were applied in some locations such as tapers, as shown in Figure 74. e permanent and temporary markings are generally in the same locations to limit the eects of ghosting. In addition, the design plans specied that fog seal should be applied in any striping removal areas on the asphalt pavement. ere was an incident during construction in which a CAV on autopilot veered sharply into a taper aer identifying tabs (exible pavement markers) as a lane line. Aer this incident, Oregon took additional steps to ensure the removal of tabs immediately aer use. Overall, Oregon believes that the temporary markings performed well on the project. Figure 74. Pavement markings in work zone on I-5 from Woodburn to Salem, Oregon. Courtesy of Oregon DOT

90 Temporary Pavement Markings Placement and Removal Practices in Work Zones Summary of Case Examples e seven DOTs described in this chapter have diverse experiences with respect to temporary markings in work zones and pavement marking removal. Some of the key ndings from the DOT interviews can be summarized as follows: • While DOTs oen have their preferred types of temporary markings, the type of temporary marking used in a particular work zone depends on a variety of factors, including duration, weather conditions, frequency of snowplowing, time of year, ease of placement, pavement type, trac volumes, and equipment availability. DOTs nd that dierent types of temporary markings are suitable for specic conditions. • Designers oen select the type of temporary pavement markings to be used in a work zone, but sometimes contractors make this decision. • Some DOTs are in the process of transitioning from the use of 4-in. markings for work zones to the application of 6-in. markings. Wider markings are sometimes applied in gore areas. • 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 diculties in nding suitable temporary pavement markings for thin surface treatments on asphalt such as chip seal, cape seal, and microsurfacing. • DOTs are evaluating and implementing various strategies in an eort to improve temporary pavement markings in work zones, including 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 typically inspect temporary pavement markings visually, with inspection frequencies ranging from daily to biweekly. • Some DOTs measure retroreectivity of temporary pavement markings. reshold values vary among DOTs and are oen based on marking color and time aer placement. • Material requirements are sometimes based on the specications for permanent pavement markings. • e level of concern for incorporating provisions for CAVs into processes for temporary pavement markings and pavement marking removal varies between the DOTs. • DOTs normally use typical applications for mobile operations for the placement of temporary pavement markings in work zones. • 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 trac. • Contractors typically select the method used to remove or cover existing pavement markings. In some cases, DOT approval is required, and standard specications sometimes prohibit the use of specic methods based on pavement type. • For a given method of removing existing pavement markings, DOTs nd that there is sometimes variability in the quality of pavement marking removal based on operator or equipment. • Contractor and equipment availability sometimes limit the range of temporary pavement markings or pavement-marking removal methods available to DOTs. • DOTs are seeking innovative solutions to the problem of ghost markings. Strategies imple- mented 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 location as the temporary markings. • Research needs identied by the DOTs include developing new materials for wet recovery and wet weather markings, eld testing and new solutions to address ghost markings,

Case Examples 91   advancing standards to encourage greater consistency between DOTs (especially with respect to provisions for CAVs), and creating a guidance document regarding the conditions suitable for different types of temporary markings. • DOTs are interested in finding out about the practices and experiences of other DOTs for temporary pavement markings and marking removal, especially with respect to perfor- mance, selecting marking types for different surfaces, placement under high speeds and traffic volumes, preparing for CAVs, materials, time constraints, enforcing contract provi- sions, using innovative types of markings, wet applications, and delineation of shoulders.