Truck Symbol

[Shoddyfrog]

Sometimes my buildings get a symbol of a truck above them, with a number in the corner. Changes from orange to red as number gets higher. What does this mean?
Don't get a production alert to hover over and get an explanation. I am guessing it means alot of trucks waiting to deliver stuff from the building are trapped due to high traffic? Although the number in the icon does not correspond to the amount of items in building waiting to leave, so not 100% about that.

[Alex, Master Penguin]

As you said, it's the size of the queue, usually due to how many dispatch orders you made, and the quality of the roads

[Shoddyfrog]

OK thanks