SP312-000110-00

VIRGINIA DEPARTMENT OF TRANSPORTATION

SPECIAL PROVISION FOR

LATEX MODIFIED EMULSION TREATMENT (MICRO-SURFACING)

August 10, 2010; Reissued July 12, 2016

I. DESCRIPTION

This work shall include furnishing and placing a latex modified emulsion to existing roadway surfaces as specified herein and as directed by the Engineer.

II. MATERIALS

A. Emulsified asphalt shall be a quick set latex modified cationic emulsion conforming to Section 210 of the Specifications and the following:

1. The emulsion shall be designated CQS-1h cationic quick setting emulsion and shall conform to Cationic Type CSS-1h.

2. Ring and ball softening point of the residue, minimum = 140 degrees F.

3. Pass towel test (VTM-89) in the 30 minutes at room temperature with job materials.

4. Residue, percent by evaporation, minimum 62 percent as determined by VTM-78.

5. Material shall be furnished according to the Departments Asphalt Acceptance Program.

B. Aggregate shall be non-polishing crushed stone conforming to Section 202 of the Specifications, except the soundness loss shall not exceed 18 percent.

Gradation of the aggregate shall be according to the following:

SCREEN

SIZE

TYPE A

(% Passing)

TYPE B

(% Passing)

TYPE C

(% Passing)

RUTFILLING

(% Passing)

No.3/8 100 100 100 100 No.4 100 90-100 70-95 70-95 No.8 65-90 65-90 45-70 45-70 No.16 45-70 45-70 32-54 32-54 No.30 30-50 30-50 23-38 23-38 No.50 18-33 18-33 16-29 16-29

No.100 10-21 10-21 9-20 9-20 No.200 5-15 5-15 5-12 5-12

C. Mineral filler shall be non-air entrained hydraulic cement, Type I, conforming to Section 214 of the Specifications or hydrated lime conforming to Section 240.02(a) of the Specifications. When requested by the Engineer a manufacturers Certification will be required.

https://covgov.sharepoint.com/sites/TM-VDOT-SC-Specifications-External/2016_Standard_Specifications/SP312-000110-00.docx

D. Water shall conform to Section 216 of the Specifications.

E. Latex modifier along with emulsifiers shall be milled into the asphalt emulsion by an approved emulsion manufacturer.

F. Additives may be used by the Contractor to provide control of the break/set time in the field. The type of additive shall be specified in the mix design.

G. Sampling requirements for gradation shall be taken from aggregate stockpiles designated by the Contractor. These stockpiles shall be located in the aggregate producer's quarry and acceptance for gradation will be based on an approved aggregate Producer's modified acceptance production control plan. Samples for Marshall tests and asphalt content shall be taken from the completed mix for testing by the Department. The frequency of sampling and testing will be established by the Engineer based upon the Department's acceptance program. The asphalt content will be determined by the Ignition Method (VTM-102) or nuclear gauge (VTM-93), as determined by the Engineer.

III. MIX DESIGN

A. The mixture shall be designed in a Department approved lab by the Contractor for the

Engineer's approval and the job mix formula shall provide the following:

1. Compatibility of latex, aggregate and emulsion according to the Schulze-Breuer

Test procedure. Other procedures approved by the Engineer may be used. The test shall be run at the design stage and when requested by the Engineer.

2. A minimum Marshall Stability of 1800 pounds when tested according to VTM-95.

3. A flow of between 6 and 16 units when tested according to VTM-95.

4. An asphalt content that produces 4.7 percent voids in total mix for surface and 6.5 percent voids for rutfilling when tested according to VTM-95.

Aggregate used in the job mix formula shall be from the same source and representative of the material proposed by the Contractor for use on the project.

B. Proportioning of the mix design shall be within the following limits:

Type A Type B Type C Rutfilling % Residual Asphalt (by wt. of dry aggr.) 6.5-8.5 6.5-8.5 5.0-7.5 4.5-6.5

% Mineral Filler 0.26-3.00 0.26-3.00 0.25-3.00 0.25-3.00 % Latex Modified-Solids (by wt. of residual asp.) 3.0 Min. 3.0 Min. 3.0 Min. 3.0 Min.

Additive As Required As Required As Required As Required

IV. EQUIPMENT

All equipment, including hand tools, shall be designed or suitable for the application of micro-surfacing and in good working condition.

A. Mixing equipment shall produce the asphalt mixture in a self-propelled, front feed, continuous loading, and mixing machine. The unit shall deliver and proportion the aggregate, emulsion, mineral filler, control setting additive and water to a revolving multi-blade shafted mixer and discharge the mixture on a continuous and uniform basis. A mobile unit will be permitted on areas less than 15,000 square yards provided a sufficient number of units are used to promote an efficient continuous type operation which minimizes disruption to traffic and provided the units are equipped with a twin shaft mixer capable of an operational speed of 60 feet per minute and have a capacity to store and mix components to produce a minimum of 5 tons of mix. All equipment shall be capable of delivering a continuous, uniform, properly proportioned, and homogenous mixture to the spreading unit.

Individual volume or weight controls for proportioning each material shall be provided and meters or counters shall be such that the Engineer may readily and accurately determine the amount of each material used at anytime.

The mixing machine shall be equipped with a water pressure system and nozzle type spray bar to provide a water spray immediately ahead of and outside the spreader box when required.

B. Equipment calibration shall be provided by the Contractor stating the current year data for each mixing unit using materials from the same sources as those to be used on the project. Data for each unit shall be in the form of a graphic scale indicating the proportioning controls settings required to obtain the residual asphalt content as determined in the mix design. Such data shall be maintained with each unit.

C. Spreading equipment shall uniformly spread the paving mixture by means of a mechanical type spreader box attached to the mixer and equipped to agitate and spread the materials throughout the box. The box shall be designed and operated so all the mixed material will be kept homogenous and moving with no evidence of premature breaking during laydown. A front seal shall be provided to ensure no loss of the mixture at the road contact surface. The rear flexible seal shall act as a final strike off and shall be adjustable.

The spreader shall be maintained to prevent the loss of the paving mixture in the surfacing super-elevated curves. The spreader box and rear strike-off shall be so designed and operated that a uniform consistency is achieved and produces a free flow of material to the rear strike-off without causing skips, lumps, ripples or tears in the finished surface. A secondary strike-off may be used to improve surface texture.

Rutfilling, when required, shall be accomplished by means of a box specifically designed for that purpose. The box shall be of one-half lane width and have a dual chamber with an inner v configuration of augers to channel the large aggregate to the center of the rut and the fines to the edges of the rut fill pass. The box shall be equipped with dual steel strike-off to control both the width and depth of the rutfill.

D. Pneumatic roller may be required by the Engineer, at no cost to the Department, if excessive loss of aggregate is observed. The roller shall be equipped with treaded tries having an air pressure of 40 – 60 pounds per square inch (psi).

V. PROCEDURES

A. Beginning work, The Contractor shall notify the Engineer at least three work days prior to beginning work. Up on request by the Department, the Contractor shall provide 6 quarts of liquid emulsion and 50,000 grams of aggregate material for the Department’s use in determining asphalt content. The contractor shall perform ignition oven calibrations and submit them with the job-mix formula (JMF) to the Department two weeks prior to the beginning of the work.

B. Surface preparation, prior to applying the paving mixture, the surface shall be thoroughly cleaned of all vegetation, loose materials, dirt, mud and other objectionable materials. Prior to paving, an asphalt tack coat Type CSS-1h diluted three parts water to one part asphalt shall be applied at a rate 0.05 gallons per square yard. When required by field conditions prewetting of the tacked surface shall be applied evenly at a rate that will uniformly dampen the entire roadway surface.

All cost for furnishing and applying the tack coat and prewetting shall be included in the price bid for "Latex Modified Emulsion Treatment".

C. Application types and rates

1. Rutfilling shall be placed by means of a specially designed rutfilling box that will leave the surface crowned between 1/8 and 1/4 inch per inch depth to allow for traffic compaction to approximately a level surface. The Contractor shall provide and use a ten foot straight edge to control the depth and crown.

2. Latex Modified Emulsion Treatment for leveling course shall consist of an initial application to prepare for the surface course. The minimum application rates shall be 16 pounds per square yard for Type B and 20 pounds per square yard for Type C.

3. Latex Modified Emulsion Treatment (LMET) for surface course shall consist of the final application which serves as the pavement surface. The LMET shall be placed at an application rate of 16 to 20 pounds of mix per square yard for Type B and 18 to 22 pounds per square yard for Type C.

Where neither rutfilling nor leveling is used, the mix application rates shall be 18 to 22 pounds per square yard for Type B and 20 to 24 pounds per square yard for Type C.

The Contractor shall provide to the Engineer aggregate weight tickets, a daily delivery summary, and an estimate of aggregate lost and otherwise not used in the work for each stockpile location (rutfilling aggregate shall be stockpiled and inventoried separately). When disagreements occur, the Engineer will make the final determination of such loss.

D. Application

The mixture shall be spread to fill minor cracks and shallow potholes and leave a high-skid resistant surface uniform in texture and appearance. Longitudinal joints shall not overlap more than four inches, except on irregular roadway widths when approved by the Engineer; however the joints shall be neat in appearance. Pavement edges shall be reasonably straight and shall be tapered to tie in neatly at gutters, entrances, and connections. When possible, longitudinal joints shall be placed on lane lines.

During night paving operations sufficient lighting shall be provided by the Contractor to insure proper application of micro-surfacing.

Rutfilling must be compacted by traffic or by a minimum of three passes with a pneumatic tire roller not in excess of 5 miles per hour (mph) prior to application of the surface course and must be cured such that applied material is totally free of detectable water. Rutfilling or scratch courses placed at night shall not be overlaid the same night or until such time that the materials totally free of detectable water.

Any oversized aggregate or foreign materials shall be screened from the aggregate stockpile prior to delivery to the mixing machine. A mixing aid additive shall be used to accommodate spreading due to slow placements or high temperatures. Additionally, water in a very limited quantity may be sprayed into the sprayed box to prevent build-up on the blades. All excess material shall be removed immediately from the ends of each run. Loose aggregate that is determined to be objectionable by the Engineer shall be immediately removed without damaging the surface.

Based upon a visual examination or test results the Engineer may reject any work due to poor workmanship, loss of texture, raveling or apparent instability.

The entire area specified shall be treated and the contract quantity shall not be exceeded.

E. Test requirements

Samples representing a maximum of 500 tons will be taken from material produced by each mixing unit for asphalt content determination. The residual asphalt content of such samples shall be within plus or minus 1.5 percent of the approved job mix. When successive tests from a mixing unit fail or one test fails by more than two percent, that unit shall be removed from service until approved by the Engineer.

F. Price Adjustment

Emulsified asphalt certified weight tickets showing the residual asphalt content shall be provided to the Engineer. Asphalt not used shall be documented and considered in determining the percent of asphalt used on the total project. Upon completion of the project, the percent of asphalt shall be determined by dividing the calculated weight of residual asphalt by the delivery ticket weight of aggregate used in the work. A one percent reduction in the unit price per ton will be applied for each one tenth of a percent the residual asphalt content is more than one percent below the approved job mix formula.

The price adjustment will be applied to the total tons for which payment is made.

G. Weather Limitations

Micro-surfacing shall not be applied on surfaces containing puddle water and on surfaces less than 50 degrees F, except that in the early morning the minimum surface temperature may be 40 degrees F provided the ambient temperature is expected to be above 60 degrees F and there is no forecast of ambient temperature below 32 degrees F within 24 hours from the time the material is applied.

H. Personnel

The Contractor shall have a Department certified Slurry Surfacing Technician on the job site to control the work.

VI. MEASUREMENT AND PAYMENT

The quantity of latex modified emulsion treatment used in the accepted portions of the work will be measured by net ticket weight of aggregate, latex modified emulsion and mineral filler delivered and incorporated in the accepted work. No deduction will be made for moisture naturally occurring in the aggregate and mineral filler.

The accepted quantity of latex modified emulsion rutfilling will be paid for at the contract unit price per ton.

The accepted quantity of latex modified emulsion treatment will be paid for at the contract unit price per ton for the type material specified.

Payment will be made under:

Pay Item

Pay Unit

Latex modified emulsion rutfilling Ton *Latex modified emulsion treatment, (Type) Ton

*(For asphalt schedule work projects the leveling and surfacing courses are shown as separate line items in the schedule of work but combine into one bid item in the schedule of items.)

SP512-000110-00

SPECIAL PROVISION FOR

SECTION 512—MAINTAINING TRAFFIC – NON-SCHEDULES (LUMP SUM)

July 12, 2016

SECTION 512 of the Specifications is amended as follows:

Section 512.03—Procedures is amended to include the following:

The Contractor shall submit a plan, sequenced with his plan of operations, to the Engineer for maintenance of traffic for his review prior to commencement of work. The plan shall be designed and implemented according to the Virginia Work Area Protection Manual, the MUTCD and the Department generated project-specific temporary traffic control plan or requirements provided in the Contract. When the Department provides a sequence of construction in the Contract, the plans or estimated quantities for maintenance of traffic items are for estimating purposes only.

Section 512.04—Measurement and Payment is replaced with the following:

Maintenance of traffic including flagger service, pilot vehicles, electronic arrows, warning lights, channelizing devices, traffic barrier service, traffic barrier service guardrail terminals, impact attenuator service, construction pavement markings, construction pavement message markings, temporary pavement markers, eradication of existing pavement markings, temporary detours, aggregate material, Type III barricades, construction signs, and truck mounted attenuators will be paid for on a lump sum basis as follows:

(a) Per structure wherein, the lump sum price bid shall be for providing maintenance of traffic for a single structure identified in the Contract by its structure number. No measurement will be made.

(b) Per route and location(s) wherein, the lump sum price bid shall be for providing maintenance of traffic for work at a specified location on a single specified route or, specified locations grouped together on a single specified route as one lump sum item.

No measurement will be made as detailed in the Contract.

The Contractor’s price bid shall include, but not be limited to; providing a person to meet the basic work zone traffic control and intermediate work zone traffic control requirements of Section

105.14 of the Specifications; furnishing, placing, maintaining, replacing, relocating, adjusting, aligning, removing, flagger service, pilot vehicles, warning lights, electronic arrow, channelizing devices, traffic barrier service, traffic barrier service guardrail terminals, impact attenuator service, construction pavement markings, construction pavement message markings, temporary pavement markers, eradication of existing pavement markings, temporary detours, aggregate material, Type III barricades, construction signs, truck mounted attenuators, and all labor, material and equipment incidental to completing this work according to the Virginia Work Area Protection Manual and traffic engineering guidelines and principles. Site specific adjustments to maintenance of traffic operations specified by the Virginia Work Area Protection Manual and the MUTCD such as quantity, location, or spacing of traffic control devices within construction limits or on any approaches to the project, required by the Engineer to improve traffic operation or safety shall be considered an alteration in the work according to the provisions of Section 104.02 of the Specifications.

The Contractor will be paid 30 percent of the lump sum bid price upon satisfactory installation of the required maintenance of traffic items to commence construction operations and active prosecution of the work. Contingent upon active pursuit of the work, the Contractor will receive https://covgov.sharepoint.com/sites/TM-VDOT-SC-Specifications-External/2016_Standard_Specifications/SP512-000110-00.docx monthly payments for maintenance of traffic based on the daily dollar amount of the bid price for maintenance of traffic until 90 percent of the unit bid price is paid. The remaining 10 percent will be paid for after all maintenance of traffic items are removed at final acceptance of the Contract.

Additional traffic control layout detail items that are determined and authorized by the Engineer to be necessary to ensure the safety of the traveling public and are in addition to the number required by the traffic control layout details in the VWAPM, the drawings in herein, and the Contract, will be measured and paid for as follows, therefore, the provisions of Section 104.02 will not apply:

● Flagger service shall include furnishing certified flagger, paddles and safety equipment.

Where additional flagger service is required, as determined and authorized by the Engineer, flagger service will be measured in hours and paid for at the rate of $15 per hour of use.

When flagger service is used for the Contractor’s convenience, such as for ingress and egress of construction equipment or materials, payment will not be made. Note: The required flaggers described in the two flagging conditions in Section 512.03(h) of the Specifications will not be measured as a separate pay item but will be considered incidental to the traffic control operations described.

● Pilot vehicles shall include furnishing vehicles, necessary warning devices, drivers, fuel and maintenance. Where additional pilot vehicles are required as determined and authorized by the Engineer, such vehicles will be measured in hours of actual use and will be paid for at the rate of $23 per hour of employed use.

● Electronic arrows shall include furnishing arrow panels, fuel, maintenance, and a truck or trailer having flashing amber warning lights for mobility of the electronic arrow. Where additional electronic arrows are required as determined and authorized by the Engineer, electronic arrows will be measured in hours of actual use and will be paid for at the rate of $5 per hour for each hour of employed use.

● Warning lights for use on sign panels or installed on traffic barrier service will not be measured for separate payment. The cost thereof shall be included in the price for other appropriate pay items. This shall include maintaining, relocating, and removing.

● Group 1 channelizing devices will not be measured for separate payment. The cost thereof shall be included in the price for other appropriate pay items.

● Group 2 channelizing devices, not designated in the Contract as a separate pay item but where additional Group 2 channelizing devices are required as determined and authorized by the Engineer, these will be measured in days and paid for at the rate of $1 per day per device. This price shall include furnishing and maintaining devices, removing devices when no longer required and signs. When group 2 channelizing devices are moved to a new location or are removed and re-installed at the same location, they will be measured for separate payment. However, when group 2 channelizing devices are moved within the lane or from one lane to another by simply moving the devices across the lane edge line without removal from the roadway, no additional payment will be made.

● Traffic barrier service will not be measured for separate payment. The cost thereof shall be included in the price for other appropriate pay items. This shall include warning lights, delineators, barrier vertical panels, fixed object attachments, patching restraint holes, fixed object attachments used on traffic barrier service in locations where existing guardrail is in place including restoring existing guardrail to its original condition, maintaining, and removing traffic barrier service when no longer required.

● Traffic barrier service guardrail terminal will not be measured for separate payment. The cost thereof shall be included in the price for other appropriate pay items. This shall include furnishing, installing, moving to a new location as directed or approved by the Engineer, and removing when no longer needed.

● Impact attenuator service will not be measured for separate payment. The cost thereof shall be included in the price for other appropriate pay items. This shall include Impact attenuators used with barrier openings for equipment access.

● Construction pavement markings will not be measured for separate payment. The cost thereof shall be included in the price for other appropriate pay items. This shall include furnishing marking materials, preparing the surface, adhesive, installation, maintaining, removing removable markings when no longer required, inspections, and testing.

● Construction pavement message markings will not be measured for separate payment.

The cost thereof shall be included in the price for other appropriate pay items. This shall include marking materials, preparing the surface, adhesive, maintaining, and removing removable markings when no longer required.

● Temporary pavement markers will not be measured for separate payment. The cost furnishing and installing pavement markers, surface preparation, adhesive, and maintaining and replacement of lost or damaged markers and removing the pavement markers and adhesive when no longer required.

● Aggregate material will not be measured for separate payment. The cost thereof shall be included in the price for other appropriate pay items. This shall include preparing the grade and furnishing, placing, maintaining, and removing material as required.

● Type III barricades will not be measured for separate payment. The cost thereof shall be included in the price for other appropriate pay items. This shall include furnishing and placing barricades, retroreflective sheeting, maintaining, relocating to new locations and removing when no longer required.

● Construction signs except those already required by the Contract (which includes those signs required by the VWAPM, the drawings herein, and such signs as “Loose Gravel”, “Unmarked Pavement”, and “Low Shoulder” that may be required by the Engineer to ensure the safety of the traveling public due to the nature of the Contractor’s operations) when determined and authorized by the Engineer, will be measured in square feet and paid for at $20 per square foot. This payment, based on square footage, shall be compensation for furnishing, placing, relocating, covering, uncovering, and removing the sign(s) when no longer needed for the duration of the project; multiple payments for the same sign used more than once will not be allowed. Such extra signs will consist of either a greater number of the standard signs already listed in the applicable traffic control layout details in the VWAPM, the drawings herein, and the Contract, or other signs included in the VWAPM but not originally considered applicable for use on this Contract.

● Truck mounted attenuators, not designated in the Contract as a separate pay item but where additional Truck Mounted Attenuators are required as determined and authorized by the Engineer, these will be measured in hours of actual use required, and will be paid for at the rate of $22 per employed hour. This price shall include furnishing the truck mounted attenuator, mounting vehicle, lights, electronic arrows, if allowed but not required, and maintenance. When electronic arrows are used at the option of the Contractor in lieu of the rotating or high intensity amber strobe light, the cost of the electronic arrow shall be included in the price for truck mounted attenuators. When electronic arrows are required and authorized as determined by the Engineer and not incidentally mounted (and permitted) on such truck mounted attenuator support vehicles, they will be paid for separately as specified herein.

● Portable traffic control signal will not be measured for separate payment. The cost portable traffic control signal equipment, installation, energy source, maintaining, adjusting, aligning, removing and relocating equipment.

● Portable Changeable Message Signs (PCMS), not designated in the Contract as a separate pay item but where additional Portable Changeable Message Signs are required as determined and authorized by the Engineer, these will be measured in hours of actual use and paid for at the rate of $15 per hour for each hour of employed use. This price shall be full compensation for furnishing or mobilizing the unit(s) to the project, maintenance, operation, and repositioning the unit(s).

Payment will be made under:

Pay Item Pay Unit Maintenance of traffic (Structure No.) Lump sum

Maintenance of traffic (Route and Location[s]) Lump sum

CITY OF FAIRFAX

SPECIAL PROVISION FOR GREEN BIKE LANE COLORED PAVEMENT

October 15, 2025

I. DESCRIPTION

Work consists of coloring asphalt pavement for bike lanes as required in Contract Documents and as directed by the Engineer.

II. MATERIALS

Bike lane color pavement marking material is to be pre-formed thermoplastic that provides durable skid-resistant surface, has long-lasting color retention, and is for use in low to high vehicular traffic areas. Bike lane color pavement marking material is to be PreMark as manufactured by Ennis-Flint, Federal Green manufactured by Integrated Traffic Systems or Swarco Preform Thermoplastic by

Swarco Industries, Inc., or approved equivalent. Bike lane color pavement marking material is to be bike lane green. Color must be homogeneous throughout thickness of material and must be such that end result of finished product visually provides surface which is uniform in color over entire surface area and which is an approximate match to specified color. Manufacturer is to demonstrate in writing, and by providing references, that pre-formed thermoplastic material has been satisfactorily used for minimum period of 2 years in areas where weather conditions are similar to those experienced in

Fairfax, Virginia area.

This material shall conform to VDOT Thermoplastic Type B, Class II paint as outlined in Sections

246.03 (c) and 704.03 (b) of the 2020 VDOT Road and Bridge Specifications.

III. PROCEDURES

Preparation of pavement surface, equipment, materials, and method of application and repair of color pavement marking material, will be as required by manufacturer.

IV. MEASUREMENT AND PAYMENT

Green bike lane paint will be measured for payment will be number of square feet of bike lane color pavement marking system constructed. Unit price bid for green bike lane paint shall include preparation of pavement surface; layout; furnishing and installing bike lane color pavement marking material; repairing damaged or improperly installed pavement marking material; protecting completed work from traffic; site cleanup; and furnishing all labor, material and equipment necessary to complete work.

Payment will be made under:

Pay Item Pay Unit

Green Bike Lane Paint Square Feet

END OF SECTION

SPECIAL PROVISION FOR

PAVEMENT MESSAGE MARKING

April 16, 2024

I. DESCRIPTION

ADD TO VDOT SPECIFICATIONS, SECTION 704 PAVEMENT MARKINGS AND MARKERS

This work shall consist of establishing the location of and installing retroreflective approach and message pavement markings in accordance with the MUTCD, the Contract and as directed by the Engineer. The approach and message pavement markings shall be white as required by the MUTCD and shall be installed as detailed in the plans approved by the Engineer.

II. MATERIALS

REFER TO VDOT SPECIFICATIONS, SECTION 704 PAVEMENT MARKINGS AND MARKERS

III. PROCEDURES

REFER TO VDOT SPECIFICATIONS, SECTION 704 PAVEMENT MARKINGS AND MARKERS

IV. MEASUREMENT AND PAYMENT

ADD TO VDOT SPECIFICATIONS, SECTION 704 PAVEMENT MARKINGS AND MARKERS

Pavement Message Markings will be measured in units of each per location and will be paid for at the Contract unit price per each. This price shall include surface preparation, premarking, furnishing, installing, quality control tests, daily log, guarding devices, primer or adhesive, glass beads, reflective optic materials when required, and warranty.

Payment will be made under:

Pay Item Pay Unit PAVE. MESSAGE MARKING, 4’, CHARACTER, TY. A Each

PAVE. MESSAGE MARKING,

APPROACH PAVEMENT MARKING, TY. A Each

Pay Item Pay Unit

Pay Item Pay Unit