What are the Alabama 350, TL-3 Previously Cast Concrete Barrier, Type 6A Specifications?

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The Alabama Department of Transportation outlines specifications regarding the proper dimensions for 350, TL-3 previously cast concrete barriers, type 6A (for use with approved impact attenuator systems), including general notes, elevation view specifications, plan view specifications, barrier section details, connector pin assembly details and lift hook details.

Alabama 350-TL Barrier General Notes

  1. This information refers to barriers cast prior to 1.01.2020. Barrier cast after this date should be MASH compliant. There will be an interim phase-in period for the new barrier during which this old barrier will be allowed. The MASH, TL-3 barrier and previously cast barrier are not interchangeable and should not be mixed in a continuous run of barriers.

  2. Supply one connector pin assembly with each 10’ barrier section.

  3. The contractor is responsible for checking the tightness of the 11#4” hex nut at both ends of the 11#4” diameter bolt to ensure that no hex nut comes loose during the duration of its use on the project.

  4. All barrier segments should be marked as shown: ALDOT, 350-TL, number and year cast. The markings should be permanently impressed in the barrier using a minimum of 2” high lettering.

  5. Barriers should initially be placed close together (closed joint) so that the pin can be easily inserted through the hinge bar loop. The barriers should then be opened (open joint) before the nut is tightened on the pin.

Alabama 350-TL Barrier Elevation View Specifications

350-TL barriers in Alabama should conform to the following dimensions and include the following features, according to the ALDOT elevation view specifications:

  • Length: 10’

  • Height: 32’

  • Drainage and lifting slot: 4’ long and 2” high; 3’-0” between the end of the lifting slot and the edge of the pane; the drainage slot should be centered on the panel

  • Two #5 lift hooks, each protruding 3” from the top of the barrier; 2’-6” between the edge of the panel and the center of each lift hook

  • One ¾” diameter hinge bar on the left side of the panel; 8-1/2” between the bottom of the panel and the bottom of the lift bar; 8-1/2” between the top of the panel and the top of the lift bar; 15-3/4” between each protruding end of the hinge bar

Alabama 350-TL Barrier Plan View Specifications

350-TL barriers in Alabama should conform to the following dimensions and include the following features, according to the ALDOT plan view specifications:

  • Width: 24”

  • Length: 10’-0”

  • ¾” chamfer

Alabama 350-TL Barrier Section A-A, B-B, C-C and D-D Specifications

350-TL barriers in Alabama should conform to the following dimensions and include the following features, according to the ALDOT specifications.

Section A-A

  • Width: 24”

  • Height: 32”

  • Distance between groundline and lowermost bar: 4-1/2”

  • Distance between lowermost bar and middle bar (BAR B #5 REINF BAR): 13-1/2”

  • Distance between middle bar (BAR B #5 REINF BAR) and uppermost bar (BAR B #5 REINF BAR): 11-1/2”

  • Distance between uppermost bar (BAR B #5 REINF BAR) and top of the panel: 2-1/2”

  • Section should be symmetrical in nature

Section B-B

  • Width of bottom of panel: 24”

  • Breakpoint: 10”

  • Upper slope height: 19”

  • Width of top of panel: 6”

  • ¾” chamfer or radius

  • Section should be symmetrical in nature

Section C-C

  • Width: 24”

  • Height: 32”

  • Distance from top of panel to midpoint: 1’-0”

  • Section should be symmetrical in nature

Section D-D

  • Width: 24”

  • Height: 32”

  • Distance from top of panel to midpoint: 9”

  • Incline on each side: 3”

  • Section should be symmetrical in nature

Alabama 350-TL Barrier Connector Pin Assembly Details

350-TL barrier connector pins in Alabama should include the following features, according to the ALDOT specifications:

  • Pin – AASHTO M314 Grade 36 (minimum)

  • Alternate hex head machine bolt – ASTM A307 Grade A

  • Nut – ASTM A536 Grade A heavy hex

  • Washer – ASTM F436 Type I

  • All components must be hot dip galvanized and ASTM A153

Alabama 350-TL Barrier Lift Hook Details

350-TL barrier lift hooks in Alabama should include the following features, according to the ALDOT specifications:

  • #4 rebar AASHTO M31 Grade 40 or 60 or ASTM A615 Grade 40 or 60 or ½” 250 or 270 KSI steel strand uncoated

  • Seven-wire for concrete reinforcement – AASTHO M203 or ASTM A416

  • Two required per curb section

This blog post is an interpretation of specifications by the Alabama Department of Transportation. Please consult with Alabama DOT's most recent requirements for definitive information.

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