Methods, systems, and apparatus, including computer programs encoded on a storage device, for monitoring a vehicle are disclosed. A vehicle monitoring system for monitoring a vehicle includes one or more processors and one or more computer storage media storing instructions that are operable, when executed by the one or more processors, to cause the one or more processors to perform operations. The operations include: receiving, from a vehicle occupancy monitor and by the vehicle monitoring system, vehicle occupancy data that indicates presence of a vehicle occupant; receiving, by the vehicle monitoring system and from a sensor, sensor data that indicates an attribute of the vehicle; analyzing, by the vehicle monitoring system, the vehicle occupancy data and the sensor data; and based on analyzing the vehicle occupancy data and the sensor data, performing a vehicle monitoring system action.