Apparently a turn is an American term for an out and back freight run, as opposed to a run from one yard that finished in another yard at the other end of the line. The North Shore Line appears to have had little in the way of freight trains running as all the reference I have so far read refer to turns that went out and back again. This is probably a product of the North Shore Line being a bridge route that hustled on the margins to get freight routed for delivery over its tracks.
So, I looked at what I thought might happen when serving Burnham Yard?
I know that at midnight connecting railroads would want to off load empties to connecting lines so as to avoid per diem charges (a surcharge for holding onto a foreign road car that would have to be paid). So I figure that the first trains of the operating day for Burnham yard would be interchange traffic from the South Shore and Roarin' Elgin to offload cars in transit.
I imagined for my scheme that the South Shore would arrive first, on the basis that it was the biggest freight hauler of the three former Insull owned lines, and that it would on average haul in five cars with say a minimum of one and a maximum of nine cars per turn (just to give the operating crew some headaches). Whereas the Roarin' Elgin having much less freight traffic would only contribute two cars per day, say a minimum of one and a maximum of three per turn.
These would arrive at Burnham yard during the first shift of the day; midnight to 08:00 hours.
The next train to arrive at the yard would therefore be a North Shore turn working the second shift of the day. Again I thought that this would average around five cars, with a minimum of one and a maximum of nine cars being hauled per turn.
All of these trains are considered to be third class.
Next I would have a fourth class local switching turn come and switch the cars that the previous train had left, and spend time readying cars to be picked up by the next North Shore Line freight train.
Finally, the last train of the day would arrive at Burnham yard, a North Shore third class freight turn that would drop cars at the interchange and pick up cars for delivery. This might arrive with five cars and depart with and equal number. I'm not sure yet as this is the one job that I haven't quite got my numbers sorted out for.