A sub-area in an area is identified as an authorized sub-area for a vehicle to access based on detecting a first object in the sub-area from first sensor data. Then a parameter of the first object is determined from the first sensor data. Upon detecting a second object in the sub-area from second sensor data, a parameter of the second object is determined based on the second sensor data. The sub-area is determined valid based on determining the parameter of the second object is different than the parameter of the first object.