Green Line route 724 is a high-profile limited-stop express bus service, currently operated by Arriva Shires & Essex as part of the large Green Line Coaches network. It operates between Harlow and Heathrow Airport, and is partly funded by the British Airports Authority (BAA). It is the only Green Line service to be operated by buses rather than coaches.
In 1998, a fleet of nine DAF SB220/Plaxton Prestige were purchased, with extra luggage space built in. These were some of the first low floor wheelchair accessible buses to operate in the United Kingdom.
These were replaced in August 2006 with a fleet of nine new Mercedes-Benz Citaro, an investment of £1.3 million. These were the result of a Quality Bus Partnership between Arriva, BAA and Hertfordshire County Council. These buses seat 39 and also have extra luggage racking. The previous DAFs were refurbished and cascaded around Arriva Shires and Essex, some now branded for route 500 (Watford - Aylesbury).
The most recent development of the route reflects the opening of Heathrow Airport's new Terminal 5 in March 2008. Service 724 will run via Terminal 5 between the Central Bus Station and Terminal 4.
From 19 May, the service was withdrawn from Heathrow Terminal 4, with another new timetable introduced. Short workings on other parts of the route became numbers 725 and 726.
* No longer serves Terminal 4 from 19th May 2008.