Methods, systems, and apparatus, including computer programs encoded on a computer storage medium that generates lane path descriptors for use by autonomous vehicles. One of the methods includes receiving data that defines valid lane paths in a scene in an environment. Each valid lane path represents a path through the scene that can be traversed by a vehicle. User interface presentation data can be provided to a user device. The user interface can contain: (i) a first display area that displays a first visual representation of the sensor measurement; and (ii) a second display area that displays a second visual representation of the set of valid lane paths. User input modifying the second visual representation of the set of valid lane paths can be received; and in response to receiving the user input, the set of valid lane paths of the scene in the environment can be modified.