Answer: Definitely could be wrong, but I would say to get raw materials to and from industrial centers.
Step-by-step explanation:
the reason why I'm choosing that is that Historians and economists agree that any industrializing society needs to have an effective transport network, to enable the movement of heavy products and materials around to open up access to raw materials, reduce the price of these materials and the resulting goods, break down local monopolies caused by poor transport networks and allow for an integrated economy where regions of the country could specialize.