620.12 Construction Inspection for Sec 620

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MoDOT Test Method TM 80
Retroreflectometer Request

620.12.1 Description

This work shall consist of furnishing and installing pavement marking either permanent or temporary in nature. Pavement marking requirements are ever changing to meet new challenges and to improve the quality. Many of the changes require change orders or order records to implement the new requirements, since many are not directly specified in contracts. Sec 105.1.1 of the standard specifications provides the authority to the engineer to determine what quality of work is acceptable. Sec 105.3.1 allows the engineer to make adjustments in pay for work deemed less than desirable but is to remain in place. In addition, Sec 620.1 specifically states that this work shall be as shown on the plans, as specified therein or as directed by the engineer. The key words here are “as directed by the engineer”, which allows the engineer to enforce new requirements or quality standards as long as the contractor is informed by the engineer of what the expectations are. However, if the requirements become too stringent, the contractor may require compensation for items not covered in the contract. Good engineering judgment needs to be applied in enforcing any new items not covered in an existing contract.

General guidelines that apply to pavement marking contracts are:

  • Surface preparation is required on all new surfaces.
  • See Permanent Pavement Markings for the current material selection guidelines.
  • Retroreflectivity readings of painted curbs are not required.
  • The alignment standards for the installation of milled rumbles are in Construction Inspection Guidelines for Sec 626.
  • Milled rumbles shall be clean and dry before the installation of permanent pavement marking. No payment will be made for this cleaning.
  • Edgeline rumble "stripes" will be installed according to the guidelines in Rumble Strips.
  • When temporary paint is used the temporary markings will meet the following:
  • Minimum Initial Retroreflectivity – 150 mcd/m2/lux
  • Minimum Maintained Retroreflectivity – 100 mcd/m2/lux
  • 95 percent of the stripe needs to be present.
When temporary paint markings fail to meet any of the above requirements, the contractor will replace the temporary markings.

620.12.2 Construction Requirements (Sec 620.2)

620.12.2.1 General (Sec 620.2.1)

(Sec 620.2.1.2)

The inspector must ensure that the striping contractor is providing pavement marking that is uniform in appearance with crisp, well-defined edges and of uniform width and thickness. It is also essential that the pavement marking has a uniform surface distribution of glass beads.

(Sec 620.2.1.3)

Longitudinal markings should be offset from joints. This is so future maintenance of the joints, crack pouring etc. doesn’t impact the markings. No line should be closer than 2 in. to a joint (See Standard Drawing 620.00).

(Sec 620.2.1.4)

No-track time is the point in the curing process at which vehicular traffic may cross the line without removing paint or beads. No-track time is dependant on the material and weather conditions when applied. Vehicles driving on wet markings damage lines by removing beads, reducing retroreflectivity and reducing the life of the line. The contractor may be liable for damages to vehicles that track the paint.

(Sec 620.2.1.6)

At ramps, the stripe within the gore area should be 12 in. wide, and beyond the gore area, reduced back to 6 in. wide.

(Sec 620.2.1.7)

Application rates are checked by calculating the yield. This is done by determining the amount of material used versus the amount of line placed. Yields for different materials can be obtained from the suppliers. Yield is determined by dividing the quantity of material used by the amount of line placed. The amounts of material used can be determined from the striper. The amount of line placed can be determined either from the foot counter on the striper or estimates of the amount placed. Foot counters on stripers are only active when the guns are actually applying material. If foot counters are used, either the foot counter should be reset to zero at the start or the initial reading needs to be recorded. The results are in gallons per mile (refer to Yield Table for Liquid Pavement Marking Materials.

Another way to check the application rate is on the fly with a wet film thickness gauge. The gauge, which is typically a rectangular piece of metal or plastic with serrated edges of different depths, is placed on a test plate immediately after the material has been placed. Test plates, which are thin metal squares and can be the same test plates used for concrete thickness testing, are placed in front of the striper during production. When doing a test the beads should be turned off when the striper passes over the plate to get an accurate reading of the wet thickness. The number of test plates used is dependent on the amount of line being placed and the discretion of the inspector.

(Sec 620.2.1.8)

When shoulders are fog sealed, fog sealing should be kept out of rumble strips that are to contain a rumble stripe. Any overspray of fog seal material should be completely removed by a method approved by the engineer prior to placement of the rumble stripe. When surface preparation or pavement marking removal is required, the method of sur-face preparation or removal shall not cause structural damage to the pavement and shall meet the approval of the engineer. For all contract work the surface preparation area or removal area shall meet the following requirements:

(a) Not be more than 1 in. wider than the pavement marking.
(b) Not be more than 1 ft. longer than the pavement marking.
(c) Not be deeper than 1/16 in. from the top of the pavement surface.
(d) Not deviate laterally more than 3/8 in. per 10 feet.

These requirements/tolerances should be enforced on projects where the surface preparation is visually unacceptable. Some infrequent surface preparation beyond these tolerances may be acceptable. The enforcement of these tolerances is left to the engineer or district’s discretion.

The engineer may enforce these requirements on any existing job as long as the engineer has informed the contractor of the quality of work expected prior to the work being performed. If the contractor is unaware of the expectations for the final work, it may be more difficult to require corrective action at the contractor’s expense.

In the standard specifications Sec 620, Sec 620.60.2, Construction Requirements for Pavement Marking Removal, and Sec 620.90.3.3, Surface Preparation for Epoxy Pavement Marking Material, both state, “The pavement surface shall not be left scarred with an image that might mislead traffic. Any excess damage or scarring of the pavement shall be repaired by the contractor, at the contractor’s expense.” It should be noted though, regardless of the method used, repair of asphalt pavement surfaces leaves an image of the repair that may still mislead traffic and diminishes the overall life of the asphalt pavement. For this reason, we want to avoid under all circumstances unnecessary scarring to pavement surfaces, asphalt or concrete. To drive this home to pavement marking subcontractors, it is believed that it is better to make monetary deductions than to have them only repair the damaged area. (The benefit of repairing asphalt pavements is questionable, and is left to the discretion of the engineer to require or not sealing of these scarred areas.) Therefore, it is recommended the following deductions in payment be made for unacceptable scarring of the pavement surface due to surface preparation or pavement marking removal operations:

  • For centerline stripes, monetary deductions should be made if more than 10 percent of the pavement markings have scarred areas outside of the allowed tolerances. If visual inspection indicates that this is the case, it is recommended the number of unacceptable and total stripes be counted, and a direct percentage deduction in the contract price be made. For example, if 20 percent of the stripes placed had surface preparation or removal areas outside of the allowed tolerances, then the contractor would be paid only 80 percent of the contract price. If the percentage were 29 percent, than payment would be 71 percent of the contract price.
  • For solid line pavement markings, such as edge lines, if visual inspection indicates 25 percent or more of the surface preparation or removal is outside the allowed tolerances, than 75 percent of the contract price for the pavement markings should be made. No varied deduction in payment as recommended for centerline stripes is recommended.

More significant contract price deductions are being recommended for centerline pavement marking because excessive scarification in the middle of the roadway is more noticeable and computations are relatively easy to make than if trying to apply a direct percentage to solid pavement markings.

On undivided roadways where solid line pavement markings are placed in combination with centerline skip pavement markings, deductions in payment should be applied as if the pavement marking was a solid line.

620.12.2.2 Permanent Pavement Marking (Sec 620.2.2)

On all major routes, all permanent pavement marking white lines and yellow edge lines should be 6 in. wide. Therefore, all divided highways, unless given an exception by the Central Office, should be 6 in. wide.

All other permanent pavement marking yellow lines, such as on the centerline of two-lane highways or other roadways where lane lines have double pavement marking stripes, should be 4 in. wide.

The location of the stop bars and traffic signal loop detectors at intersections are critical. Improper location of these two features in relation to each other can cause operational problems with the traffic signals. Ideally, the two features are located so that when a vehicle stops at the stop bar, the stopped vehicle is fully in the detection zone of the loop. Care also needs to be taken when side street left turns are present. Locating the stop bars too far forward in these situations can either make it difficult for the side street traffic to execute their left turn or the turning traffic could clip the loop, thereby putting a false detection into the signal.

When intersection markings using durable materials, such as the 3M tape, are to be installed at intersections with traffic signals, the installation sequence of the detector loops and permanent pavement marking is important. Coordination of the layout of stop bars and loops with traffic personnel is encouraged for proper placement of both. The detection loops should be cut and sealed first, followed by placement of the stop bars. This sequence is recommended so that the durable pavement marking tape is not cut or damaged by the saw cutting process for the detector loops. The grooving required for installing the tape should not damage the loop detectors, since the loop cuts are significantly deeper than the grooving. Following these steps will provide the good, clean look that we want on projects and will allow the permanent pavement marking, such as 3M tape, to provide the durability that we are expecting.

620.12.2.3 Inspection (Sec 620.2.3)

Permanent pavement marking should be inspected following installation. Final measurements for retroreflectivity should be taken no sooner than 14 days from placement of the pavement markings and no later than 45 days following placement. It is important to wait 14 days to allow traffic to remove excess beads that are not embedded into the paint and to wear off any paint film that may be on the surface of the embedded beads. Measurements taken in this timeframe (14-45 days) generally results in the most favorable initial readings as long as the contractor avoids tracking mud, tack or other debris onto the pavement markings.

Retroreflectivity testing should be conducted when pavement markings are dry and no visible moisture is on the road surface. Fog and condensation of morning dew should not be considered as acceptable weather conditions. Testing should not be done immediately after snow events. Testing should be done after salt from snow removal operations is washed away by rain. Retroreflectivity testing should be done during daytime hours only.

For construction projects 0.5 mi. or shorter, portable handheld retroreflectometers, such as the Mirolux 30 retroreflectometer, should be used in lieu of a mobile retroreflectometer to take retroreflectivity readings on permanent and temporary pavement marking. Measurements should be made in accordance with MoDOT Test Method TM 80. All measurements should be made in the direction of traffic flow, except on the centerline of two-lane roads where the required number of measurements should be made in each direction. Both single and double lines are to be measured, and the acceptance criteria should be applied for each line in both directions. Inspectors should realize that the Mirolux 30 machine normally shoots a beam of light approximately 6 to 12 inches. in front of the machine's lens. Therefore, the lens should be located approximately 6 to 12 in. from the flat area of rumble stripes. When the light falls in the bottom of the rumble, the retroreflectivity readings are usually lower than the backside or top of the rumble area because of the change of light beam angle, and for that reason, care should be taken to avoid taking readings in the bottom of the rumble. If handheld retroreflectometer results are disputed by the contractor, a mobile retroreflectometer may be requested for dispute resolution.

For construction projects longer than 0.5 mi., a mobile retroreflectometer should be used. Mobile retroreflectivity readings are taken by a third party contractor hired by MoDOT. To provide the third party contractor with the required information for taking the readings, the Retroreflectometer Request form should be completed and sent to the Construction and Materials Division as soon as the markings are placed.

For all maintenance contract projects, regardless of the length of project, retroreflectivity measurements are provided by the contractor with an approved third party contractor using a 30- meter geometry retroreflectometer. The readings are to be performed as required by each individual contract.

A conscientious contractor will take readings with a handheld unit during the course of the work. Inspectors should also spot check retroreflectivity with a handheld unit as a quality check of the work. Where handheld units are shared among project offices, planning and coordination are necessary to ensure a unit is available when its needed. These initial readings should not be used for final acceptance, but may be used for determining partial payment for the work performed prior to receiving mobile retroreflectometer readings. For more detail, see Acceptance below.

620.12.2.4 Acceptance (Sec 620.2.4)

(Sec 620.2.4.1)

Acceptance or rejection should be based on the acceptance requirements given in Sec 620.2.4 of the standard specifications or as required by the contract, such as specified for maintenance contract projects which are usually less stringent.

For projects 0.5 mile or shorter, the acceptance readings are based on the readings taken by the engineer with a hand-held retroreflectometer. For cases in which six or three sample size measurements are taken, calculate the average. If the average falls below the minimum required value, reject the pavement marking. For cases in which 20 sample measurements are taken for a segment of roadway, if 17 or more readings in a 300 ft. section, or actual length for intermittent longitudinal lines less than 1000 ft., for that segment of roadway are above the minimum value required, accept that segment of pavement marking. If four or more readings within a segment are below the minimum value required, calculate the average value of the failed readings and use the calculated average to determine, if applicable, the amount of deduct that applies to that segment, or if that segment of pavement marking needs to be removed and replaced.

For projects longer than 0.5 mile, the acceptance readings are based on the mobile 30-meter geometry retroreflectometer readings provided by a third party contractor hired by MoDOT to do the testing. The mobile retroreflectivity data is supplied in 0.1 mile intervals and should be reviewed by the engineer for acceptance.

Currently there is not an approved method for applying epoxy pavement marking over existing epoxy pavement marking, and if not done properly, could pop off within a year or sooner. Spraying over new epoxy pavement markings with low retroreflectivity readings is not recommended at this time, and removal is considered drastic if the retroreflectivity readings aren't too low.

Deductions for epoxy pavement marking, based upon average readings obtained using hand-held retroreflectometers or 0.1 mile interval readings using a 30-meter geometry retroreflectometer, are recommended to be:

At this time, apply the above deductions only to epoxy pavement marking.

The above recommended deductions are in the process of being evaluated by reviewing historical information on retroreflectivity values of existing epoxy pavement marking. The undergoing evaluation will not be completed until one more year of data is attained. At that time, recommendations for deductions will be finalized, based on actual data, and be implemented into the specifications.

Although these deductions are not part of current specifications for epoxy pavement marking, current specifications require complete removal and replacement at the contractor’s expense if retroreflectivity readings do not meet the values given in Sec 620.4.1 of the standard specifications. Therefore, because the above deductions may be more suitable to the contractor, the contractor should be given the option of taking a deduct in payment where applicable, based upon the above table, in lieu of total removal and replacement.

Under current specifications the contractor cannot be paid for installed permanent pavement markings until mobile retroreflectivity readings have been received and processed by the resident engineer. As a result, pavement marking contractors are not receiving pay for their work, on average, until 60 days after installation. This delay in payment is causing a hardship on these contractors and is not in line with the concept of the Prompt Payment Act that MoDOT has earnestly supported. To reduce this hardship to some degree, it is recommended that REs consider partial payment of pavement markings after initial inspection of the work and a preliminary evaluation of the retroreflectivity of the pavement markings. Depending on the comfort level of the RE with the initial inspection of the work and past performance of the pavement marking contractor in the RE's area, one of the following procedures is suggested to determine the amount of partial payment to be made to pavement marking contractors:

  • If past performance of the pavement marking contractor, in regards to retroreflectivity readings, have ranged at or above the 80 percentile of the minimum specified retroreflectivity requirements, a nighttime drive-thru by the engineer or inspector may suffice to feel confident that the pavement markings will meet retroreflectivity requirements. If this is the case, payment of 80 percent of that due to the contractor for installed pavement marking is recommended. The key to acceptance for partial payment based on a visual drive-thru inspection is how the contractor’s past performance has been on previous projects. This method of inspection is not recommended for contractors who have provided marginal work in the past.
  • When past performance of the pavement marking contractor has been marginal or the drive-thru inspection provides questionable results, the RE should take some retroreflectivity readings with a handheld retroreflectometer at some random locations. The number of readings taken is left to the RE or district's discretion, but should not be less than 20 readings per mile. The amount of initial payment should be based on the results of the handheld retroreflectometer readings, using the deduct table to determine the percent of payment that the contractor will likely receive after mobile retroreflectometer readings. The initial payment should subsequently be adjusted accordingly, but is recommended not to exceed 80 percent. Please note, do not take any retroreflectivity readings until seven days after the pavement markings have been installed. Readings taken prior to seven days may provide erroneous retroreflectivity values. Where possible, take readings without or with minimal traffic control measures. When traffic control is required, the pavement marking contractor should provide it at their expense. If the pavement marking contractor refuses to provide traffic control, then no payment should be given to the contractor until the mobile retroreflectometer results are received. Regardless if traffic control is required or not, the pavement marking contractor should be informed when the readings will be taken and given an opportunity to have a representative present during such testing.

Although the above procedures will not provide statewide consistency, this is the only viable alternative that can be quickly implemented now. Each engineer and district should be fair and consistent as much as possible in paying for this work. It is recommended not more than 80 percent ever be paid up front prior to receiving mobile retroreflectivity readings.

A chart designating retroreflectivity acceptance requirements and payment adjustments for painted and durable pavement marking lines can be found in Sec 620. Due to the rough and irregular surface of Seal Coat, the chart includes a lower (pass/fail) threshold of 150 millicandelas/m2/lux for this type of surface. This lower requirement only applies to Seal Coat placed in accordance with Sec 409 and does not apply to scrub seal, microsurfacing, UBAWS, open-graded hot mixes, or any other type of pavement surface.

On maintenance restriping contracts, the intent is to require retroreflectivity readings that comply with the retroreflectivity numbers in the specifications. However, consideration of pavement condition needs to be part of the equation. Sections of roadways where retroreflectivity numbers indicate replacement should be physically inspected to determine the pavement condition. Pavement surfaces that are rough, broken, cracked, raveled or severely aged may not meet the retroreflectivity requirements of a good surface. The inspector should use engineering judgment to determine what impact the pavement condition has on the quality of the line if it isn’t covered in the contract. Please note, most maintenance restriping contracts now provide less stringent retroreflectivity requirements. Another factor that can impact the retroreflectivity readings is the width of the line read. Where the new line has been placed on an old line that is 5 in. or wider, the retroreflectivity readings may be impacted by the old line beyond of the new stripe. In such cases, retroreflectivity readings should be adjusted accordingly.

620.12.2.5 Temporary Pavement Marking for Milling, Grinding and Resurfacing Operations (Sec 620.2.5)

On all projects, temporary pavement marking on intermediate lifts of asphalt or concrete work that are to receive additional layers should be either preformed short term marking tape, temporary raised pavement markers (rpms) or paint. (Although not specified as a temporary pavement marking alternative in Sec 620.2.5 of the standard specifications for pavements undergoing milling, grinding or resurfacing operations, paint is not detrimental to any pavement surface and may be used in lieu of preformed short term marking tape or temporary raised pavement markers as a "no cost" change order.)

The purpose of the temporary raised pavement markers is to provide guidance to motorists during times when the permanent pavement markings are not present during maintenance and construction projects. Temporary raised pavement markers shall be maintained in accordance with the standard plans.

For diamond ground surfaces when there are problems of getting rpms to stay, it is recommended that construction grade liquid nail be used. Another option, instead of using rpms on diamond ground operations on divided highways, is to allow the contractor to grind the inside lane first, and then place a temporary centerline paint stripe on the newly ground inside lane. For a short period, until the outside lane is diamond ground, a double centerline will be present, which is acceptable. The key to allowing this is to ensure that the temporary centerline stripe is placed in the same footprint that the permanent centerline pavement marking will be installed. If not, the temporary centerline stripe will need to be removed by the contractor at the contractor’s expense after the permanent stripe is in place. Note, this striping operation will result in the permanent stripe to be on the left side of the longitudinal pavement joint, and although the standard plans show that the line should be on the right side of the joint, placing the permanent centerline pave-ment marking on the left side of the joint is permissible for these jobs.

On diamond grinding operations, when the existing pavement edge line is ground away as part of this work, temporary raised pavement markers shall be placed in accordance with the standard plans should be placed on the shoulders. In the cases where the shoulders are unpaved, tape should be placed in accordance with the standard plans for resurfacing projects. Pavement marking paint or preformed short term marking tape does not have to be removed prior to the placement of subsequent lifts. Leaving these pavement markings in place will not affect the performance of subsequent HMA or concrete lifts. However, temporary raised pavement markers will have an impact on subsequent lifts and should be removed prior to placement of additional pavement structure.

All jobs with paved shoulders wider than 4 ft., Type 1 rpms are to be placed in lieu of tape once the edge line is removed or covered. Temporary raised pavement markers are required to be removed by the contractor after installation of permanent pavement edge markings.

For visibility and safety, it is critical that the following standards are enforced:

(1) Temporary lane marking durations of less than two weeks need to be placed in accordance with Standard Plan 620.10. Specifically, lane markings with temporary tape or paint shall be 4 ft. long with 36 ft. gaps.
(2) In accordance with Sec 620.2.5.2 (Section 620), any temporary pavement marking damaged, displaced or missing should be replaced at the contractor’s expense within two hours upon notification from the engineer with the following exception.
(3) In accordance with Sec 620.2.2, on roadways opened to traffic, permanent pavement marking should be in place no later than five days after final paving operations. In all other cases, operations should be scheduled, as much as possible, to comply with Sec 620 of the standard specification. For projects requiring permanent pavement markings to be installed in rumble strips, the final paving operation should be considered as the time of completion of the rumble strips. However, operations should be mobilized by the contractor to minimize the time between when the traveled way was opened to traffic and when permanent pavement markings are installed. For such operations when the roadway is opened to traffic for an extended time with temporary pavement markings, it is critical for the contractor to maintain the pavement markings strictly in accordance with the specifications, especially temporary pavement edge marking requirements.

620.12.3 Preformed Pavement Marking Tape (Sec 620.10)

Permanent pavement marking tapes typically require a primer to be applied before the tape is installed. The inspector should request a copy of the manufacturer’s installation requirements before the job begins to make sure they understand what needs to be done for a proper installation. If Type 2 tape is specified, it is to be installed in a groove in the pavement. Manufacturer’s recommendations on grooving for their product should be requested and reviewed before the work is started. For grooving installations, the inspector should make sure the groove is clean before the tape is installed. Whether ground or not, it is important that dust and grinding debris not be allowed to reenter the area where the tape is being applied. This is especially important under windy conditions and during the time when the primer is curing before applying the tape. Also, the dust and grinding debris need to handled properly. The dust needs to be controlled like any pavement cutting operations and the grinding debris needs to be disposed of in a licensed facility.

620.12.4 Paint for Pavement Marking (Sec 620.50)

Cold weather paint can be substituted for the normal waterborne paint if there are temperature considerations when the paint is to be applied. Normal waterborne paint shouldn’t be used if the temperature is below 50° F. If the temperature is below 50° F but over 35° F, cold weather paint should be used. Paint has a cure or "no track" time that is dependent on weather conditions. The cooler the weather the slower the cure time. Humidity is also a factor in the "no track" time for waterborne paint. High humidity will slow the cure time. Paint lines will normally cure to a "no track" condition in 2 to 3 minutes. However cooler temperatures or high humidity can increase this time significantly. Heating of the paint during cool weather can decrease the "no track" time. Glass beads are normally applied at a rate of 10 to 12 pounds per gallon of paint used (refer to Typical Application Rates of Pavement Marking Table). However, with the performance requirements of Sec 620.2.4, contractors may choose to use higher application rates. Be careful, flooding the line with too many beads can actually hurt the quality of the line. This happens because there is too much glass on the surface and the beads will block each other out. It is the contractor’s responsibility to meet the retroreflectivity numbers, so the inspector may just want to caution them that too many beads could hurt the quality of the line.

620.12.5 Pavement Marking Removal (Sec 620.60)

Covering over pavement markings with oils, paint or other materials is not allowed. This is because these coverings eventually wear out and the line becomes visible again.

620.12.6 Temporary Raised Pavement Markers (Sec 620.70)

(Sec 620.

Temporary raised pavement markers should be used for surface treatment projects as defined in Sec 413 when temporary rpms are specified, specifically on micro-surfacing surfaces, scrub seals, ultrathin bonded asphalt wearing surfaces, fog sealing applications, and bituminous or concrete crack sealing or filling operations. In such applications, the temporary raised pavement markers should be placed with a protective sleeve. After the maintenance application, the protective sleeve should be removed by the contractor at the contractor’s expense.

620.12.7 Epoxy Pavement Marking Material (Sec 620.90)

620.12.7.1 Material (Sec 620.90.2)

Type A Epoxy Marking (Sec 620.90.2.1) Type A epoxy pavement marking is a slow-cure material and may be substituted for Type B epoxy on new pavements not open to traffic or on pavements open to traffic where adequate traffic control can be provided during the curing period as specified in Sec 620.2.1.4. If substituted, this should be a no cost change order.

Type B Epoxy Marking (Sec 620.90.2.2) Type B epoxy pavement marking material is a fast-cure material suitable for all epoxy pavement marking applications and is the preferred epoxy pavement marking material. Type B epoxy may be substituted for Type A epoxy for all situations. Negotiation of a cost reduction for such substitution should be pursued if there is known material or labor savings, but should not be a reason for denial for such substitution. A change order should be made for such substitutions.

620.12.7.2 Construction Requirements (Sec 620.90.3)

(Sec 620.

Epoxy pavement marking material is a two-component material that is mixed immediately prior to application. The equipment should be capable of thoroughly mixing the components to manufacturer’s recommendations prior to application. No longer do we limit what method that the contractor my use to mix the epoxy. Satisfactory results is the only criteria.

Being a two-component material, it is very important that the contractor mix the parts in the correct proportions. Normally, epoxy is a 2 to 1 mixing ratio. Failure to mix the components correctly can cause the material to be discolored and/or can dramatically slow the cure time.

(Sec 620.

Surface preparation is required prior to placement of epoxy pavement marking. On new asphaltic concrete pavement, cleaning operations should not begin until after the mat has reached ambient temperature. The extent of cleaning on new asphaltic concrete should be so that 75 percent of the stone substrate is exposed. This cleaning criteria applies to rumble stripes as well. Depending on the time between cleaning operations and installment of epoxy rumble stripes or the type of cleaning operations used, the rumble strip may require to be air blasted or swept to remove loose debris in the bottom of the rumble strip.

(Sec 620.

All existing pavement marking should be removed to the extent that 95 to 100 percent of the existing marking is removed. Where temporary pavement marking paint has weathered over the winter months and subsequently has substantially been removed, the surface preparation, if deemed appropriate by the engineer, may only consist of a method that will satisfactorily clean the pavement surface. Caution should be taken to allow only surface cleaning. If the temporary paint covers the existing pavement surface to the extent that it will prevent the epoxy to bond with the pavement surface, the epoxy pavement marking will pop off when the paint loses adhesion. If existing epoxy pavement markings are in good condition and will not interfere with or otherwise conflict with newly applied markings, existing epoxy pavement marking may remain if approved by the engineer. Removal operations should be conducted in such a manner that no more than moderate color or surface texture change results on the surrounding pavement surface to ensure that the surface mix remains sealed. The engineer should make the determination of acceptable removal. The above guidance is based on recent information that surface preparation, including the removal of existing epoxy markings, is the best practice for achieving quality epoxy pavement marking.

Surface preparation and the epoxy pavement marking should be kept aligned, if not, the epoxy pavement marking may pop off outside of the preparation area. The surface preparation area should also be kept to a minimum beyond the permanent epoxy pavement marking width for aesthetic reasons, and in the case for asphaltic concretes, to minimize the surface area exposure to environmental elements. Refer to guidance for Sec 620.2.1.8 for additional information.

For diamond grinding projects, surface preparation needs only to consist of sweeping or whatever it takes to remove any loose debris from the pavement surface prior to placement of the epoxy pavement marking.

Basis of Payment (Sec 620.90.3.6) A new line item adjustment type has been added in AASHTOWARE Project (AWP) titled "Retroreflectivity Adjustment". Please associate any adjustment based on the criteria provided above in Acceptance (Sec 620.2.4) to this new adjustment type.

Guidance for Acceptance (Sec 620.2.4) provides deductions for unacceptable retroreflectivity epoxy pavement markings. A new line for adjusting the price for epoxy pavement markings has been added to AWP, titled "Retroreflectivity Adjustment," for this purpose. Applicable deductions should be made by a change order, as follows: Underrun the original pay item at the contract unit price for whatever quantity is not being paid at the full contract unit price, then include a line or lines as necessary showing the same item number, but now as an overrun with the applicable adjusted unit price.

620.12.8 Snowplowable Raised Pavement Markers

New installation of snowplowable raised pavement markers has been discontinued for all roadways.

620.12.9 Snowplowable Raised Pavement Marker Rehabilitation

620.12.9.1 Construction Requirements

It is recommended a Type III epoxy mixed with aggregate in accordance with Sec 1039.50.1 be used to patch holes left by the removal of a SRPM.