I once saw a woman come out of a bank branch and drop a large bundle of banknotes as she got into her car. I picked up the money, tapped on her window, and handed it back to her. She looked furious as she took the money and drove off without even a 'Thank you'.
I took it as being shock and anger at herself, rather than any animosity towards me.

The workman at your traffic lights was probably aware of how serious it could have been, and his anger was at the faulty lights, not at the drivers.