BusTalk

[bystander]

About 1963 I visited San Francisco and one of the things I did was ride some Trackless Trolleys. I noticed that when we were getting under way, the driver would push a little silver button and the bus would move out up the hill. I asked about it, and he told me it was a "Field Shunt" whatever that means. I asked him what would happen if he pushed it while taking off from a level traffic light. He said he didn't know because he'd never tried it. Well, in awhile, we were on the level and sitting at a traffic light. "Yes?" i said.

"Yes" he said and when the light changed, he pushed the button and floored the power pedal leaving a couple of very surprised cars sitting at the light.

[N4 Jamaica]

I wish I knew electrical terms better, especially as I am a big fan of PCC streetcars, introduced to Brooklyn the year I was born. You might google "pcc cars and field shunts." I recall a trip to Boston in the early 1950's and how beautifully the PCC's accelerated in the subway, often starting jack-rabbit around a curve when leaving a station. The designers of the PCC had supposedly researched the amount of acceleration standees could bear, and they used this knowledge to make the cars rapid. Sometime in the 1970's, I recall reading in the railfan press that the field shunts had been removed from the PCC fleet to simiplify repairs and that would make for weaker acceleration.
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I have done that bit of Google research, and field shunts seems a way to give extra oomph to a starting vehicle. On this Bus Talk website within the past year, I think I read that New York's Orion hybrids were hitting people on the street, people who did not expect a stopped bus to accelerate quickly and quietly. Instead of adding an automatic horn tap or some other noise, I think I read that the TA slowed the acceleration! The lawyers rule the schedules.
I'm sure that if you read the old advertisements for trackless trolleys, you would find a quantified rate of acceleration. Imagine if automobile manufacturers were told they had to design cars without zip!