This article is from the James Taylor FAQ, by Joel Risberg (email@example.com) with numerous contributions by others.
Here, in JT's own words, is the explanation for Steamroller. This is
transcribed from the 1970 JT/Joni Mitchell BBC radio show bootleg:
We played this eight-month long gig at a place called the Night Owl Cafe
down in Greenwich Village in New York. It used to be a McDougal and Third,
but it might have moved since then. I don't know.
Anyhow, at that time there were a lot of so-called blues groups in New York
City, you know? And they were making a lot of noise with electric guitars
and amplifiers that their parents had bought them for Christmas and
birthdays and stuff. Their idea of soul was volume. They'd just crank it
up, you know? And they were singing all these heavy songs like "I'm a Man"
or "I'm a Jackhammer" or "I'm a Steamship", whatever..."I'm the Queen
Mary" [laughter] ... "I'm a Ton of Bricks."
And we weren't to be left out of all this so I wrote this next song, which
is the heaviest blues tune I know, ladies and gentlemen....called "I'm a
Steamroller." [more laughter as JT goes on the play a hilarious solo
version of the song]