A Force Node Diagram of the U.S. Interstate System

There’s nothing too complicated about this post. I’ve been interested in creating an illustration of the U.S. Interstate system for awhile but my initial concept of a “subway-style” diagram of the network had already been done. After some recent experimentation with the D3 Javascript library, I decided that it might be interesting to try out a simple force node display using the Interstate’s control cities as the nodes. Control cities are certain major destinations that are used to provide navigational guidance at key decision points along a particular route. It should be noted that not all control cities are actually cities and not all cities qualify as control cities. My starting list can be found here.

After my initial data collection, I found I had that I had to modify my approach to improve the network. First of all, I had to add some nodes for certain highway-to-highway connections, especially those that occurred in remote areas. I also had to include some cities that had multiple Interstate highways passing through because they weren’t always listed on each route. Finally, I added a few non-Interstate roads where I thought it made sense, including Alaska (which doesn’t actually have any Interstate highways) and eastern Canada, which has a major highway called the King’s Highway or Ontario Highway 401 linking Toronto and Montreal to key American cities.

Here is the result … click on the picture to get to a fully interactive version.

The size of the nodes is related to the estimated population of the city/destination and the color represents Census division (plus Canada). You can kind of see a rough outline of the U.S., with the Midwest roughly in the center of the diagram (in orange) and the two coasts wrapping around on either side. Hawaii and Alaska float alone at the edge and the Florida penninsula (in the South Atlantic, in red) protrudes out toward the bottom of the chart.