Here's a old and presumely still mercury, Westinghouse HMA-60 that's at a parking lot. Thanks to form109 for providing me with the manufacturer and the model of the fixture.
Main St. here in Buffalo used to have these on massive 30 foot ornate S-arm poles with huge transformer bases on them. Those old poles were large enough to support traffic signal span wires as well.
30 foot poles with 6 foot s-curve arms. The reason why I say they are massive is because the poles themselves are about the same size as current four bolt traffic signal span wire poles.