In binary networks, the focus is on whether or not a connection between two nodes exists. However, not all links (or nodes) are created equal, particularly when it comes to transportation networks. When we know about the presence of a link as well as the strength of that link, it is called a valued network. For instance when traveling from A to B in a street network, there is usually discontinuity in street type. In other words, one might move from a local street to a collector road to an arterial road and then back to a collector before reaching their destination. While engineers know this sort of differentiation as functional classification, it is also referred to as hierarchy.