 As part of the move to replace London's articulated buses, a commitment made in the 2008 London Mayoral election, the articulated buses on the 507 and 521 were replaced when their contracts expired in 2009.The articulated Citaros were replaced by new 12 metre rigid versions.On 25 July 2009 a weekend service was introduced on route 507, the first weekend service for a Red Arrow route.