Its not the speed, its the distance between the stops.. Let me give you an example...in the midwest USA there is a short commuter line called South Shore that

Its not the speed, its the distance between the stops.. Let me give you an example...in the midwest USA there is a short commuter line called South Shore that runs from SouthBend Indiana to southern shore of Lake Michigan and up to the Loop in Chicago Most of the stations on the South Shore are either blocks apart or a few miles apart..which negates a high speed rail solution