Originally Posted by
mbstone
The numbers on a runway refer to the compass direction, the runway number is the number of degrees past true north / 10. In other words if you are at the threshold of Runway 18 you are headed due south, and the other end of the runway is numbered 36. If there is more than one runway in the same direction, the leftmost would be numbered, say 18L and the rightmost, 18R. DFW has triple runways in parallel numbered 17L, 17C, and 17R (35L, 35C and 35R at the other end). LAX has 25L and 25R at the south side of the terminal and 24L and 24R at the north.
In the case where there are 4 or more parallel runways, the runway number would be shifted by 1. e.g. DTW has 4 parallel runways. So, there's a 4L, 4R, 3L, and 3R. Before the 4th runway was built, the runways were labeled 3L, 3C, and 3R.
- Pat