(Adds quotes, detail) By Julien Pretot PARIS, April 13 (Reuters) - French railways filed a complaint on Monday after riders ignored level crossing barriers during the classic Paris-Roubaix race and were almost hit by an express train as television viewers watched in horror. "Several riders deliberately went through a level crossing in the town of Wallers, in violation of all safety regulations," the SNCF said in a statement. "Millions of TV viewers have seen, live, this very serious and reckless infringement that could have been tragic." Observing that 29 people had died in accidents around crossings last year, the SNCF said stopping trains during the race -- which is steeped in history and famed for daunting cobbled stretches -- would have caused "utter chaos". The International Cycling Union (UCI) described the incident as "extremely worrying" and said it had "requested a comprehensive report... for review and possible action". More...