ROYALSLOT RTP SLOT In this mode, aircraft take off towards the west and land from the east over London, thereby minimising the impact of noise on the most densely populated areas. To further reduce noise nuisance, the use of runways 27R and 27L is swapped at 15:00 each day if the wind is from the west. When runway alternation was introduced, aircraft generated significantly more noise on departure than when landing, so a preference for westerly operations during daylight was introduced, which continues to this day. When landings are easterly there is no alternation; 09L remains the landing runway and 09R the takeoff runway due to the legacy of the now rescinded Cranford Agreement, pending taxiway works to allow the roles to be reversed. Heathrow's two runways generally operate in segregated mode, whereby landings are allocated to one runway and takeoffs to the other. Best of all, the sheets of plastic are so inexpensive that scientists can change their designs on the fly and see their work in action in just minutes instead of days or weeks.|Railway Coupling by Country