Angela Green, 44, from North Moor Estate in York, was found guilty of level crossing misuse at York Magistrates’ Court.
She pleaded not guilty but after being convicted was fined and given three points on her license.
Police say Green failed to obey the signals at Bootham Level Crossing in York last October and passed over the crossing on a red light and as the barriers were coming down.
A member of Network Rail staff captured the incident on a mobile phone and gave evidence that led to her conviction.
Inspector Richard Price from British Transport Police said: “Despite our constant warnings about using level crossings safely, unbelievably Mrs. Green put her life at risk through her actions.”