At the time this Metrocar's full-sized version was at the test track [Middle Engine Lane - where the Stephenson Museum is now] I was working for the Passenger Transport Executive.
4001 and 4002 were traipsing up and down the test track almost everyday for several hours - perhaps to see what faults might develop ? I went to watch several times and had a few driving lessons - including helping to test the emergency braking system [as in pass the STOP board and trip the full brakes, you come to a halt very quickly indeed].