An Amtrak ACS-64 "Cities Sprinter" leads a set of MARC commuter cars out of the Center City Commuter tunnel and over the aqueduct that connects downtown Philadelphia's Suburban Station with 30th Street Station across the Schuylkill River. To the right, a long 6 car set of SEPTA Silverliner's runs in the opposite direction. The reason for this unique event which took place over the Summer and Fall of 2016 and into 2017 was to make up for a shortage in capacity as the result of SEPTA withdrawing its recently delivered Silverliner V's from service after an inspection discovered a design flaw necessitating repairs to the fleet. There's a prototype for everything suggesting those mismatched trains you ran on your layout as a child may actually have been authentic after all, lol!