Fort Worth-based BNSF Railway and a leading railroad workers union have reached a tentative agreement to allow one person to operate a train on routes protected by a new collision-avoidance system required by Congress in 2008.A BNSF spokeswoman confirmed the agreement with the International Association of Sheet Metal, Air, Rail and Transportation Workers. If ratified by union members, it would cover 60 percent of the BNSF system.Under the agreement, a sole engineer would operate most trains with the support of a remotely based “master conductor” on routes equipped with Positive Train Control.The agreement was first reported Thursday by Railway Age, a trade publication.BNSF spokeswoman Roxanne Butler said the agreement would not apply to trains carrying large volumes of hazardous materials, including crude oil and ethanol. BNSF is the largest hauler of crude oil by rail in North America.A Federal Railroad Administration emergency order last August required a minimum of two employees for such trains. Last July, an unattended crude oil train derailed in Lac-Megantic, Quebec, igniting explosions that killed 47 people. A lone engineer was in charge of the train.The Transporation Safety Board of Canada has yet to release its findings on the causes of the disaster.