O
O.R.C. Conductor. (See Big O)
O.S. 1) On Schedule. 2) To report the passing of a train.
Observation Car Passenger carrying vehicle, usually at rear of train, with windows and seating arranged to give maximum view of passing scenery.
Occupied Camp Car Signal A white circular sign with black letters, which must be supplemented by a white light at night. When displayed, it signifies that employees are in, around, or in the vicinity of camp cars.
Oilcan Tank car
Offsider [AU] See Second Person
Old Girl Affectionate term for steam engine.
Old Hand Experienced railroader usually with high seniority. Also called old head.
Old Man Superintendent or general manager.
Ole Hoss Salvage warehouse, or freight on hand.
On The Advertised According to schedule; right on time. Often called on the card (timecard) and sometimes on the cat hop.
On The Carpet Commoner version of dancing on the carpet.
On The Ground Used to describe a derailment.
On The Spot See Spot.  (See Spot run. Run, Spot, run. Sorry, I couldn't help it.)
Op Telegraph operator.
Open Air Navigator Hobo riding freight on top.
Open The Gate Switch a train onto or off a siding. Close the gate means to close the switch after the train has passed it.
Operation Lifesaver Nationwide railroad public safety outreach program.
Operator (Opr) The person in control of a designated section of track who is accountable to the Dispatcher for movement of trains.
ORC Old Reliable Conductors, The union that represented conductors during the mid to late 19th century.
Order Board See Board.
Originating Line Haul Road The railroad on which any freight shipment starts.
Originating Station The first station on each subdivision from which a train is authorized to occupy the main track.
OTM Other Track Material.  Materials other than ties and rails ... spikes, bolts, tie plates, rail anchors, beer, etc.
Out When a trainman is at a point other than his home terminal, either on or off duty, he is out.
Outlawed See dogcatchers.
Over The Knoll Getting up the hill.
Overhead Electric wire strung above the track which supplies power to electric locomotives.
Overhead Bridge Any bridge whether railroad, automotive, or pedestrian, which crosses above the trackage.
Overhead Line Haul Road Any railroad or railroads between the originating line haul road and the terminating line haul road. Also known as a bridge line haul road.
Overhead Route (Also called Bridge route or bridge traffic.) Freight which is delivered by one railroad to a second railroad for delivery to a third railroad.
Overlap Where two block signals control the same stretch of track.
Overlap Sign A sign marking the limit of control of a block signal.