I would like to determine a bit of history about crossing gates. In particular, when hand operated gates gave way to motor driven.
Hmm…good question. I know that orginally, trains needed riders riding on horseback down the city streets to warn of the oncoming train with the dirty and noisy steam engine (Many horses would get spooked.) As time wore on, I believe the early gates were designed, porbably wood, with a hand crank that a corsing guard would lower and raise with a hand crank. I suppose sometime later motors were added with the advent of automotic gates. I would bet the change happened with a really large increase in traffic, because the cranking of the gates wasn’t the problem, it was really when to raise/lower them.
(Automatic crossing protection was availible with trolley for a long time-the pole along the wire would trip a switch on one side of the crossing, and trip another on the other side of the crossing. I think the switch before the crossing was magnetic, and when the shoe hit it, it knocked in place, completing a circuit, activating the magnet to hold the contact in, and therefore turning on the crossing. One across, the shoe on the wire would hit another switch (spring loaded), probably knocking it off for a second. While the circuit was broken, the first magnet would loose its magnetism, and physically drop out of contact. This broke the circuit, turning off the crossing, but the only break was before the crossing - this meant that it was reset for the next car to come by.)
I think modern crossing gates (at least early modern automotic crossing gates) are raised and lowered when a train enteres their “block.” A circuit is created between the two rails. When a train enters, an electrical connection is made between the two rails, and the circuit is complete, and the gates come down.
There is also current technology that adjusts the timing of when the gate falls to the speed of the on-coming train. It is called a “constant warning” system. In Ohio, it is almost standard procedure to install this in all new or upgraded grade crossings.
B&O had manual gates at Mckeesport, Pa. at least until 1969 although automatic gates were available long before that date.