As Mr. Brown is about to pull his gun on the conductor, a man in a black jacket is seen entering the train. Then Mr. Brown pulls his gun and tells the conductor that when the person leaning against the first car (Mr. Blue) gets on, he is to close the doors. The same man in the black jacket gets on again.
When the gang separates the train and backs it up to separate it from the train, the young conductor says in amazement, "I didn't know these things went backwards." Cute, but this is a very unlikely line from an apprentice conductor "studying to take the motorman's exam." Besides the usual running back and forth while making up trains in the yards, every subway car runs in both directions, because they usually do not turn the train around at the end of the line. Instead, the operator stops at the last station, walks from the former front to the former back, switches controls to the new "front end" and goes back the way he came. So all subway cars spend half of their life "going backwards," as any conductor would know.
During Garber's tour with the Japanese visitors, he says that each train is named for its "terminus" and time that it departed. Thus, he says, a train leaving Woodlawn at 6:30 would be named "Woodlawn 630." Woodlawn is not the terminus (end of the line) of such a train, but its beginning.
At the end of the film, Patrone and Garber are investigating 9 subway motormen from the list of those fired. Presumably all in one day, they see one in a wheelchair, one at a tollbooth, and Longman. When they're at Longman's apartment door, Garber asks Patrone how many more suspects from the list they still need to see that day. Patrone answers, "6, 7, I don't know." Apparently both of these highly trained and experienced cops have very short memories, or can't count to three.
The first car of Pelham 1-2-3 as it enters 28th St. is car 7339. However, at Grand Central, 7339 is seen on the opposite track across the platform. On top of that, the first car in the tunnel after being cut from the rest of the train is car 7434.
When Pelham 1-2-3 initially enters 28th St. the front "Brooklyn Bridge" destination sign on 7339 has wide lettering. Later, when 7339 comes to a screeching halt after being tripped by a red timing signal, the "Brooklyn Bridge" destination sign has narrow lettering.
When Bud Carmody closes down the rear section of the train at 59th St., there is a noticeable gap between the train and the edge of the platform. When he closes down the front section, there is no such gap.
After cutting away the rest of the train, Mr. Green, Mr. Brown and Bud Carmody walk up and climb into the head car. In the next shot, Mr. Green enters the motorman's cab while in the background, Carmody and Mr. Brown can be seen climbing into the car again.
When Mr. Green first enters 59th street station, an R16 NYC Subway car is seen leaving with the designations of a 6 train (2:16). Seconds later, Green then goes downstairs to catch an R22 train that is also a 6 train (2:45).
The relevant section of the Lexington Avenue Line includes curves sharp enough to have speed-controlled signals. As Mr. Green would have known, these cannot be cleared to green in advance of the train's arrival and will not clear if it is running away.
There are no switch-points - nor have there ever been any, between the local and/or express tracks on the IRT's Lev. Av. Line from roughly 40th Str. downtown to about 16th Str., yet frequently tunnel shots supposedly between the 33rd Str. Sta. and the abandoned 18th Str. Sta DO show points.
Departing the 42nd Str. (Express) Station for the 33rd Str. (Local) Sta. those downtown tracks - and only those, receive a switchpoint whereby the 42nd Str."shuttle" joins the Lexinton Avenue line... Those points are shown BUT in the opposite/wrong direction. (Either the scene is using a different set of points somewhere else in the System OR that scene was somehow edited-in to the film BACKWARDS.)
The sub-machine guns used by the gang are the Smith and Wesson M-76 9mm. There are a couple of scenes where Mr. Grey pulls the bolt back and releases it, letting fall into the chambered position. First the M-76 would have locked the bolt back in an open bolt configuration, making the gun ready to fire. Secondly, had any ammunition been in the magazine, pulling the bolt back and letting move forward onto the chamber, it then would have fired as all open bolt guns would have.
Hand-held 2-way walkie-talkie type radios were not (and still are not) functional in the NYC Transit subways and tunnels. Midway through the movie, two officers are shown communicating in this manner in the tunnel.
The action takes place on the local downtown Lexington Avenue Line, which terminates at the abandoned City Hall loop station, just past Brooklyn Bridge station. While the fact that the train in the film runs to the inner loop at South Ferry (where some express trains terminate) may appear to be a goof, the hijackers request that the switches be set in order to put them in the South Ferry loop - and there is indeed a switch onto the downtown express tracks, right before the Brooklyn Bridge station. At the time the film was made, the Lexington 5 and 6 lines went to South Ferry station. That section of track is still there but no longer in use.
When the money is being raced uptown, the motorcycle escort does not race ahead to clear intersections. When time is of the essence, this is standard procedure. The city had plenty of time to make sure the route was fully secure before the money ever left The Federal Reserve Bank.
Mr Blue has demanded that all the signals to West Ferry must be showing green, yet at the first station the train approaches, 23rd Street, the signal is clearly showing red and the train passes it without being tripped.
When Mr. Green pulls out of 28th Street, we see him disengage the "Dead Man's Feature" (by pressing down on the throttle with his hand). However, he does not actually move the control lever to make the train move. In that position, the train is at "idle" and will not accelerate.
The phone that the Mayor uses to take a call in his bedroom has buttons under the dial pad which must be depressed in order to receive a call on that particular line. When he is seen talking on the phone, none of the buttons are depressed
When the police car carrying Inspector Daniels and Lt. Garber returns to 17th street (just after Mr. Green has climbed out of the emergency street exit), the police car screeches to a stop. Tire marks on the road are already visible at the same spot where the car stops, indicating previous takes.
The goof item below may give away important plot points.
When Mr. Blue decides to kill himself at the end of the movie by placing his foot in contact with the third rail, Robert Shaw looks down before he falls, which would have been impossible if he were dead.