The FHWA adopted Section 7 of the 1985 AASHTO publication entitled “Standard Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals” for implementation beginning in July 1990. This section requires more stringent breakaway characteristics. TxDOT’s previous design of roadway illumination assemblies (based on a 1975 AASHTO specification) does not meet these requirements.

Breakaway light poles rely on frangible transformer bases to provide the breakaway feature. The 1985 AASHTO specification provides for a maximum change in momentum of a 1800 pound car to break the pole away. The 1975 AASHTO specification provided for a similar change in momentum except that the test vehicle weighed 2,250 pounds.