Caption: CN train no. 501 (CN 8894 West, at left) departs Sarnia Yard for Port Huron, MI while alongside in the yard there is a flurry of activity as train 331 (middle, power not in shot) has just arrived and is in the process of yarding its train while a yard job works local cars in the secondary "C" yard behind the photographer. Meanwhile another yard job waits for 331 to clear up so it can continue the process of classifying cars in the main yard.