To me, the load should be 'unsecure' as I'm sure the load doesn't have low self esteem. However, so far I haven't been able to find out how the actual law is written but it seems both are used.
What do you think it should be?
Do you know the correct wording?
~~~~~Edited: The correct word is actually "insecure".
"Operating vehicles with insecure cargo prohibited" = here is how it's written. Huh.Interesting.