Lighting systems built under the previous requirements should be maintained with ’75 AASHTO standard poles and transformer bases currently in stock.

Replacement transformer bases for lighting systems built under the ’85 AASHTO requirements should be specified to be the same model number as the bases being replaced. This model number is required to be incised on the base.

Two variables of pole construction affect structural compatibility with the ’85 AASHTO transformer bases top: bolt circle and base plate thickness. No tolerances for these variables have been established. For this reason, TxDOT does not recommend the direct replacement of ’75 AASHTO standard transformer bases with ’85 AASHTO standard transformer bases for 50 foot steel poles.