Originally Posted by
WHBM
I guess you've never been to the USA, where many major airports have intersecting runways and use them to INCREASE capacity. Most notable was Chicago O'Hare before the recent additional runway building, 6 runways in a star shape, 3 equilateral pairs, not unlike the original Heathrow arrangement, they used to use ALL SIX at once (co-ordinated, of course) in a spectacular bit of capacity management, and also to give some noise alleviation to the adjacent communities.
You're not really comparing apples with apples here.
Heathrow was never designed with a view to simultaneous operations from intersecting runways. The star layout was intended to allow operation from any pair of parallel cross runways when the wind did not permit safe operation from the east-west runways (bearing in mind that aircraft crosswind limits were much lower in those days).
It's true, of course, that before 23 closed it was used from time to time for landings at the same time as takeoffs from the main runway(s) but, as Gonzo points out, no amount of "spectacular capacity management" could achieve the movement rate obtainable from the two main runways.
Chicago, on the other hand, with its (now) 9 runways spread over an area more than double the size of Heathrow has evolved its runway layout over years on the assumption that intersecting runway operations will be the norm.
Heathrow, incidentally, achieves almost two-and-a-half times as many movements per year per runway as O'Hare does ...