I'm guessing the thinner lines are 3" wide and the center line is 12" wide. leaveing a 1" strip of body color between the 2.
My guess is that the 1" strip was done with some 1" wide masking tape.
The painter masked off all except for a 20" section in the center of the car. He then added 1" strips of masking tape to make body colored strips. He then painted the 20" section white and removed the masking tape to make the 1" body color strips.