ExSp33db1rd
That's about it......the use of the runways is alternated between landing and take-off under an agreement with local authorities to spread the noise impact, sorry, reduce the average noise impact on each centre-line.
That will disappear, obviously, if mixed-mode operation is introduced at LHR (ie take-offs and landings on both runways throughout the day to enable ATC to maximise the movement rate taking all factors into account) to increase LHR runway capacity, which is why the locals are up in arms against that.
The present alternating use is NOT to reduce wear 'n tear!