At around 4:50 p.m., southbound train No. 362 struck Isaacson in his Honda in the area of Whipple Avenue and El Camino Real.
Caltrain spokeswoman Christine Dunn said that traffic came to a stop to yield to a fire engine and that Isaacson had stopped on the tracks and was unable to move. The train, which was traveling approximately 60 mph, was unable to stop and struck the vehicle.
Isaacson, a Redwood City resident, was pronounced dead at the scene, according to the San Mateo County coroner's office.
The crash briefly affected the northbound track and the southbound track was open by 6 p.m.
Caltrain is cautioning drivers to always allow enough room to avoid being trapped between crossing gates or by other vehicles when crossing railroad tracks, and to never stop on the tracks.