Source: Adapted from Dr. William Anderson, University of Windsor.
National transportation networks are usually independently established and connected to other networks on an ad hoc basis. Comprehensive international infrastructure projects are uncommon since they require advanced forms of cooperation. The above figure shows a hypothetical transportation network that is bisected by a border. Since the facilities needed for border inspections are expensive to build and maintain, there are usually only a few (in this case two) crossings, creating a few links that are subject to congestion and making the whole network vulnerable to the disruption of those links. Naturally, this problem is exacerbated when a river forms the border because each crossing requires bridge, tunnel, or ferry infrastructure, which are also expensive to build and maintain. For this reason, the goal of the complete elimination of border facilities can also lead to more highly connected transportation networks. The most relevant example is the European Union with its Trans-European Transport Networks (TEN-T) strategy, aiming at improving connectivity through multimodal infrastructure investments.