Message From The President

摘要

In the January Message from the President, I discussed the benefits of high-level boarding and the related safety and clearance considerations for mixed-use railroads. This month, I conclude by further exploring the experiences of the South Shore Line (SSL). For its first modern high-level boarding platform, the SSL laid gauntlet tracks with the diverging track aligned for the boarding platform and the main track aligned for use by freight and express passenger trains. The pantograph security envelope and overhead contact system (OCS) were determinants in selecting the lateral offset of the gauntlet track. Electrified trains on either the gauntlet track or main track would operate under the same, singular OCS system to be centered midway between the two track centers which were offset by 28 V* in. Thus, the contact wire would ride on either the left or right side of the pantograph depending on the track being travelled. Number 10 turnouts were chosen under the assumption that allowable speeds over the switches would be in excess of the speed of trains arriving and departing the platform. Power-operated switch machines would be dual-control with a permanent hand-throw lever that could be quickly unlocked and thrown in the event of control failure.