Abstract: Methods, systems, and apparatus, including computer programs encoded on computer storage media, for identifying choke points in an environment. One of the methods includes obtaining road data representing a plurality of roads in an environment; identifying one or more blockage points in the environment; generating a graph representing the environment, wherein: the graph comprises a plurality of nodes and edges, each node of the graph represents a respective location in the environment, each edge between a first node and a second node represents a road that connects the location in the environment represented by the first node and the location in the environment represented by the second node, and blockage points are not represented by nodes in the graph; processing the graph to determine a minimum cut of the graph; and determining, using the minimum cut of the graph, one or more choke points in the environment.