648Traffic Impact Attenuator

648.1 General Description

This work includes furnishing and installing impact attenuator units/arrays to conform with plan locations and details and/or as directed by the Engineer. All impact attenuator units/arrays shall be tested and approved at the specified NCHRP 350 and/or MASH Test Level.

648.1.01 Definitions

General Provisions 101 through 150. Gating-A gating end treatment allows a vehicle impacting the nose or the side of the unit at an angle near the nose to pass through the device Non- Gating-A non-gating end treatment is capable of redirecting a vehicle impacting the nose or the side of the unit along the unit’s entire length.

648.1.02 Related References

A. Standard Specifications General Provisions 101 through 150 B. Referenced Documents National Cooperative Highway Research Program (NCHRP) Report 350. American Association of State Highway and Transportation Officials (AASHTO) Manual for Assessing Safety Hardware (MASH) ASTM A 123/A 123M QPL 64 AASHTO Roadside Design Guide (RDG)

648.1.03 Submittals

A. Installation Drawings Submit all required certifications, test reports and drawings of details for completing the installation. Obtain Engineer’s approval of these documents before beginning work on attenuator installation. Portable Impact Attenuator arrays shall meet the requirements of Ga. Std. 4960 and manufacturer specifications. B. Manufacturer’s Information Submit certification from the manufacturer that the attenuator unit/array and its interconnecting hardware replicates an NCHRP-350 and/or MASH approved attenuator in an accepted letter from the FHWA. Furnish items such as manufacturer’s brochures or specifications that completely outline the manufacturer’s recommendations for materials and installation methods. All workmanship and materials are subject to the Engineer’s approval.

648.2 Materials

A. Attenuator 1. Ensure that materials are in accordance with the manufacturer’s recommendations, specifications and details. 2. Use attenuators that have been classified as “accepted” by the Department’s Office of Materials and Research and approved by the Federal Highway Administration (FHWA) as meeting NCHRP-350 and/or MASH for the test level specified. 3. Where restoration and/or repair cannot be accomplished without the necessity of removing the unit/array from the original location, ensure replacement unit/array installation upon removal of the damaged unit/array. Furnishing, installing and maintaining the replacement will be at no additional cost. 4. Where required, ensure the approach end of the attenuator is equipped with a reflectorized object marker in accordance with plan details. The object marker may be furnished by the manufacturer of the attenuator or by others. Ensure that the front most section of the unit (the "nose") is yellow in color unless specified otherwise. 5. Where required, use an approved back-up system as specified in the plans. 6. For non-gating attenuators, anchor the attenuator to the pavement according to a system recommended by the manufacturer for the type pavement encountered. 7. Use Class "A" concrete for concrete pads, concrete back up if used, and concrete transition where required. 8. Use metal components and hardware galvanized according to ASTM A 123/A 123M unless otherwise specified. Ensure all metal components and hardware of permanent attenuators are free of corrosion when shipped. 9. In freezing conditions, water and sand filled attenuators shall be freeze treated according to the manufacturer’s recommendations.

648.2.01 Delivery, Storage, and Handling

A. General General Provisions 101 through 150.

648.3 Construction Requirements

648.3.01 Personnel

General Provisions 101 through 150.

648.3.02 Equipment

General Provisions 101 through 150.

648.3.03 Preparation

General Provisions 101 through 150

648.3.04 Fabrication

A. Design Criteria and Type Selection The Impact Attenuator Unit/array Type will be shown on the plans and designated by four characters. • First character Indicates the type of permanent installation. The letter "P" designates a permanent (non-gating) installation that is considered reusable. Reusable installations have major components that may be able to survive multiple impacts intact and can be salvaged when the unit is being repaired. Some of the components, however, need to be replaced after a crash to make the entire unit crashworthy again. The letter “S” designates a permanent (non-gating) installation that is considered low-maintenance and/or self-restoring. Low-Maintenance and/or self-restoring installations either suffer very little, if any, damage upon impact and are easily pulled back into their full operating condition, or they partially rebound after an impact and may only need an inspection to ensure that no parts have been damaged or misaligned. • Second character Designates the required NCHRP 350 and/or MASH test level. • Third character Indicates the traffic flow direction(s). The letter "B" indicates bi-directional traffic typical for median applications or when the unit is installed on the shoulder of a two-lane, two-way traffic facility. Bi-directional means traffic flows in opposite directions at the site of the attenuator installation. The letter "U" indicates uni-directional traffic flow typical for gore areas. Uni-directional means traffic on both sides traveling the same direction, from the nose to the rear of the unit. The letter "S" indicates traffic flow in one direction on a single side only, typical for a unit located on the outside shoulder of a roadway with one-way traffic and the other side of the attenuator not being exposed to traffic. • Fourth character Indicates the numerical value of the width, in inches (millimeters), of the base of the rigid object that the attenuator will be shielding. At bridge columns, this character is typically the width of the column plus the barrier base widths on the column sides at the pavement surface. B. Example A Type P-3-U-60 attenuator designates a permanent non-gating reusable installation tested and approved at NCHRP 350 and/or MASH test level 3 Uni-directional traffic flow a 60 in. (1500 mm) wide base for the rigid object being shielded. Temporary portable units/arrays may be either gating or non-gating based on construction sequencing and/or field conditions, See Specification Section 150. Unless otherwise specified, all permanent attenuators shall be non-gating.

648.3.05 Construction

Field locate the position of the attenuator nose as shown on the plans prior to beginning the installation. Have any variations approved by the Engineer. If the length of the attenuator unit/array is less than that indicated in the plan details for the specified conditions, the length of the concrete transition section or the length of the longitudinal barrier shall be increased as needed to provide a proper beginning point for the attenuator nose as shown in the plans. The length of the system will be the combined length of the attenuator unit/array, the back-up system and any required transition. The length of the system shall not be excessive to the extent that it intrudes appreciably within the clear offset distance as shown on the plans. The increased length of transition or barrier is considered as an incidental part of the system and will not be itemized separately. Temporary portable units/arrays shall be installed, moved, reinstalled and maintained as required.

648.3.06 Quality Assurance

Obtain certification from the manufacturer that the impact attenuator unit/array installed meets all required approvals and specifications and furnish these to the Engineer. Furnish any mill test/galvanizing test reports and heat numbers for all metal components of the unit per current requirements of the Department's Office of Materials and Research.

648.3.07 Contractor Warranty and Maintenance

General Provisions 101 through 150.

648.4 Measurement

Each traffic impact attenuator of the type specified, complete, in place and accepted at its location will be measured by the unit/array, including components, hardware, anchors, incidentals, freeze treated water or sand, and labor for each installation shown on the plans or as directed by the Engineer. Site preparation work, as described under 648.3.03, Preparation is measured and paid for separately under the respective items involved unless otherwise specified. Temporary units/arrays will be measured for payment only once, regardless of how often they are moved. See Specification Section 150.

648.4.01 Limits

General Provisions 101 through 150.

648.5 Payment

Impact Attenuator Units/Arrays will be paid for per each type specified. Payment is full compensation for all materials, labor, and incidentals necessary to complete the Item including installing, moving, reinstalling and maintaining Units/Arrays as required. Payment will also include the back-up system and transitions where required. Payment will be made under: Item No. 648 Impact attenuator unit, Type P- Per each Item No. 648 Impact attenuator unit, Type S- Per each

648.5.01 Adjustments

General Provisions 101 through 150.