(A) Metra trains share tracks with freight trains where ground vibrations may already be present.
(B) In this case, impact of new Metra service is assessed as follows.
(1) Infrequently used freight rail corridor: if two or less trains per day, commuter rail impact is assessed using FTA criteria.
(2) Moderately-used freight rail corridor: if up to ten trains per day and impact criteria are already exceeded, then commuter rail causes no impact if its vibration is five dB lower than the freights. Otherwise, Metra will use the FTA criteria.
(3) Heavily used freight rail corridor: if commuter trains are less than half the number of freights, then no impact exists unless the commuter train vibration exceeds the vibration levels of the freights.
(4) In an existing freight corridor where the project includes a new track closer to vibration-sensitive sites, impact will be assessed if the existing train vibration levels are increased significantly. A significant increase is three VdB or more.
(Ord. MET 02-25, passed 8-16-2002)