On the near side of the vehicle there are 4 sensors equally placed along the body which indicate when an object or person is within a certain distance when the left indicator is on.
Inside the cab is a “Traffic Light” which indicates how close something is to the vehicle, green being somewhat near and following to amber and red as this object gets closer and closer.
The sound system warning
As well as having this mini traffic light to signal proximity of objects next to the left-hand side of the vehicle, there is a speaker just behind the cab on the near side which calls out “Warning: Vehicle Turning Left”.
The sound warning will only go off when stationary or when driving at less than 10mph and when signalling left. It will not sound if driving more than 10mph and indicating, nor will it sound if it is stationary with the hazard lights on.
These sensors and warnings are to protect not only the vehicle and driver, but to protect potential accidents to cyclists and other vehicles that come up close.