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Lately, I have had string of overlay projects where an overlay is matching into an existing bridge. The existing bridge rail is at the correct height above the existing deck. If we match into the existing bridge rail at least part of the thrie beam would have to be installed at a lower level to match into the existing bridge rail and transition to the correct height.

Has a thrie beam transition been crash tested at a lower height than 31-inch and passed TL-3 or TL-2 crash testing?

Do you know of any options to matching thrie beam into an existing barrier when the roadway is getting an overall and the bridge is not?

See below for my quick thoughts!

Has a thrie beam transition been crash tested at a lower height than 31-inch and passed TL-3 or TL-2 crash testing?

**I am not aware of crash testing on reduced-height thrie beam AGTs at either TL-2 or TL-3. At TL-2, I would expect that a 2-in. overlay could possibly be accommodated in the transition region. Since the bridge rail and deck are at the appropriate elevations, it would seem reasonable to consider milling down the road surface prior to adding new surface overlay.

Do you know of any options to matching thrie beam into an existing barrier when the roadway is getting an overall and the bridge is not?

**Consider shifting guardrail and AGT blockouts upward on posts and capping bridge rail with similar height adjustment for at least 150-200 lineal ft beyond roadway overlay and onto bridge. Then, the height adjustment for bridge rail could be gradually ended.