 On 2 June 2002, the remaining two Red Arrow routes 507 and 521, became the first London Bus routes to be converted to articulated buses.A fleet of articulated Mercedes-Benz Citaro O530Gs entered service from that date.Being commuter routes, and so little used outside peak times, these routes were suitable to test the articulated on, and resembled the original standee bus concept, now with off bus fare collection.