"Maintain runway track". Well a track must have a starting point... in this case what is the starting point ?
Errr, how about the departure threshold, or that too obvious?
Stop splitting hairs guys, the instruction is a simple attempt to describe to the pilot an ATC requirement to maintain over the extended runway centreline on climbout when "runway hdg" might not take into account drift and "straight ahead" is less precise?
Anyone got a better idea?