 Following the June 22, 2009, collision, Metro implemented a policy of no longer placing 1000-series railcar pairs at the ends of trains in order to prevent telescoping in a collision, as they were the weakest rolling stock, structurally.The new policy placed 1000-series cars in the center of six and eight-car trains, with rail cars of other series in the end positions.The 7000-series cars started replacing these cars starting in 2016.