• a train, a locomotive, a train station, a subway station
• an airplane = a plane
• a bus, a double-decker bus, a bus stop
• seasons: spring, summer, fall/autumn, winter
• in fall, in winter
• a taxicab = a taxi, a cab
• a traffic light = a traffic signal, traffic lights, a stop sign, stop signs
• a car race, a running race, a marathon, a 10-K race = a 10-K, a runner, runners
• the starting line, a checkpoint, checkpoints, the finish line
• at the starting line, at checkpoint one, at the finish line
• fans, announcer

• The train is at the station.
• The bus is at the bus stop.
• The woman is at the bus stop.
• The taxis are at the traffic light.
• The taxi is at the stop sign.

• A point has zero dimensions. A point has no dimensions.
• A line has one dimension. A line has length.
• A square has two dimensions. A square has width and height.
• A cube has three dimensions. A cube has length, width, and height.

• The runner's at the starting line.
• The runners are at the checkpoint.
• The runner's at the checkpoint.
• The runner's at the finish line.
• The fans are at the finish line.
• The announcer's at the finish line.

• There are two traffic lights. The taxi cabs are at the traffic light.
• There are two stop signs. The taxi cab is at the stop sign.

No article is used when a train station is named:

• The train is at the station.
• The train is at Grand Central Station.
• The train is at Shinjuku Station.
• The train is at Gare du Nord Station.

The article is optional when a bus stop is named:

• The train is at the bus stop.
• The train is at (the) Jackson Street bus stop.
• The train is at (the) Howe Avenue bus stop.