sentences:  In April 2016, drivers belonging to the ASLEF trade union refused to pick up passengers using DOO on the new Class 387 trains on the Gatwick Express route.This is the system currently used for the 10-car Class 442 used on Gatwick Express, but the union claimed that extending this to 12-car trains put too much pressure on the driver and was unsafe.The operators Govia Thameslink Railway took legal action, and the union ultimately dropped the claim.