Blind in this sense does not mean not knowing where it is going, the hobo knows that. It does not mean empty either. The "blind" that you ride is a baggage car which has one exit to the next car in one direction, but no exit in the other. It is often the mail car next to the engine. It is blind in the same sense a cul de sac is blind, you cannot get out that way. So for instance a blind is used for a mail car to give extra security, it cannot be entered from the train driver's end. This also appeals to the hobo who need only watch one entrance for railway police or worse. The term is well established by the 1890s. A definition appears in Scribner's Magazine XXIX 429/1 1901, "The train's got a blind baggage car on... that's a car that ain't got no door in the end that's next the engine."

"riding blind" = riding [a] blind [baggage car]

The earliest phrase is "beating the blinds", meaning to steal a ride on such a car. Later one sees "jumping the blinds" and "riding the blinds". He is not asking to ride on the outside but on the inside in a car which usually would not be empty. The implications if the engineer is caught letting hobos ride in the blind baggage car are considerable, it is a free ride where there are things which could be stolen, often mail. - Craig Jamieson