by ExadiNigel » Sun Nov 29, 2009 3:47 pm
The black triangles differentiate the height restriction signs (top and bottom) and the width restriction signs (side to side).
Looking in the highway code, the warning sign for the height restriction appears to have a large black triangle at he top and a small black triangle at the bottom. The round prohibition sign has 2 black triangles of equal size.
Nigel
Ex - ADI & Fleet Trainer, RoADAR Diploma, National Standards Cycling Instructor, ex- Registered Assessor for BTEC in Driving Science, ex-Member RoADAR & IAM, Plymouth, ex - SAFED registered trainer