I am doing a test game and I can't achieve anything near 100% utilization in the end factory. The problem is that there are two conditions for calling freight from the supplier: sufficient capacity in storage and sufficient capacity in the inbound network of goods. If either of these conditions is not met, more cargo is not produced and the transportation network sits idle. As soon as the end consumer gets below its stockpile level, a burst of activity happens until either enough goods in transit hits the limit or another delivery arrives and overloads the stockpile at the consumer again.
As I indicated in my other post, I think the easiest solution to this issue is to significantly raise storage capacity at the consumers (or even remove the limit completely). This allows "in transit" to be the primary controlling mechanism through which freight is throttled so that a well planned network can achieve 100% factory utilization. This smooths out the demand curve so that as the end consumer uses up 10 units of cargo, another 10 is demanded on the network (or, a total transit time change is made through a more/less fast network). Now we get 10 added to supply every time 10 is consumed rather than these bursts of new cargo every time the stockpile is below storage limits.
Example:
Coal merchant: 70 storage
Network can hold 400 maximum cargo based on avg transfer time
Boat leaves colliery with 400 units cargo and reaches coal merchant 1 month later. Coal merchant consumes this stock while the boat returns to the colliery. While the coal merchant is consuming this inventory, the colliery and its dockyard are not receiving any new cargo. Once the coal merchant is below 70 units, it will then call for more cargo, spurring the colliery in to action to produce a bunch more coal. This coal is loaded on to the returning boat and zips off back to the coal merchant. Meanwhile, the coal merchant runs out of coal and sits idle for half a month or more until the next shipment arrives.