Definitions:
the top or highest part of something, especially one forming a point

the highest point of achievement; a climax

the point in turning a corner when the vehicle is closest to the edge of the track.

reach a high point or climax

turn (a corner) very close to the edge of the track

a system of reduced fares for scheduled airline flights and railway journeys which must be booked and paid for before a certain period in advance of departure