Around 7:45, an 83-year-old man drove onto the tracks near Seminary Avenue and Front Avenue, Maryland Transit Administration spokesman Terry Owens said.
"The elderly gentleman became disoriented in the fog and wound up on the light rail tracks," he said.
Passersby helped the man from his car before a light rail train crashed into the vehicle, Owens said.
Owens said that no one was injured in the crash. Light rail trains were being diverted to a single track Monday evening so police could investigate, he said.
Baltimore Sun reporter Michelle Deal-Zimmerman contributed to this article.