The context for this map is here. Basically, it’s showing the degree to which streets, pulled from OSM, are connected at both their ends, or not. Dead-ending streets were identified recursively (details in the link) and assigned negative weights. The centroids of street segments were then rendered with a 5km radius kernal density, weighted by length. Warm colors are more connected than not.
The two cities shown are Cincinnati and Dayton. Cincinnati is divided by the Ohio River.