Logistic routes created by depots are primarily useful for longer distances, as they can save you money on dispatch costs.

You start them by putting in a request on the receiving warehouse (where you want goods to go). Make sure to set the "store up to amount" to whatever amount should be stored in the warehouse.

Next, you'll want to build a truck depot at the providing warehouse and at the receiving warehouse.

The depots will get to work as soon there is another matching depot with a warehouse in range, that can fulfil the request. Goods should flow from providing warehouse - providing truck depot - receiving truck depot - receiving warehouse. Make sure the truck depots are connected by road to each other, and the warehouses.