He uses a stick to detect obstacles, and has to be guided around buildings.

They have 'sophisticated sensing technology' that can 'detect obstacles in their path, including pedestrians or other vehicles', says the company.

Cameras and sensors detect obstacles, in case, say, people wander into the car's path.

You seem to be getting a false signal — the sensors detecting an obstacle where there isn't one.

Being able to detect obstacles and terrain hazards significantly increases the safety of both manned and unmanned agricultural vehicles.