Also, several other interurbans to as high a standard as the Air Line – though at a much smaller scale – were built. In 1907, the Philadelphia and Western Railroad opened its Upper Darby–Strafford line near Philadelphia with maximum grades of 2%, no grade crossings, and an absolute block signalling system (Middleton 1968, p. 109). And after World War I, the railway tycoon Samuel Insull upgraded the interurbans around Chicago, and station-to-station averages as high as 70 miles per hour were frequently attained (Middleton 1968, p. 67). Parts of these lines are in use even today.