A train which derailed in Philadelphia on Tuesday night, killing at least seven people was travelling at over twice the speed limit when the driver hit the brakes.<br /><br /> Although the black box recorder still needs to be fully analysed, investigators know the speed was too fast for the stretch of track.<br /><br /> Robert Sumwalt of the National Transportation Safety Board said:<br /><br /> “Maximum authorised speed through this curve was 50 miles per hour (80 kilometres per hour). When the engineer-induced brake application was applied, the train was travelling at approximately 106 miles per hour (170 kilometres per hour).”<br /><br /> #Amtrakcrash: What we know <br />• Brakes slowed train from 106mph to 102mph <br />• Speed controls not installed in area CNN pic.twitter.com/GMzqakn72I— OutFrontCNN (OutFrontCNN) May 13, 2015<br /><br /> Seven carriages were derailed in the incident and more than 200 people were injured.<br /><br /> The authorities have still not accounted for every one of the 243 people believed to have been on board.<br /><br /> As well as
