Explain to employer that you used lights as a warning,easier to hit than the horn. It's unbelievable the risk some drivers take with wagons,when I was in car,I gave them bags of room,but when in wagon,I was startled sometimes at the risk car drivers take. If they only realized,it only needs a touch from a fully laden wagon to send them careering out of control. Something like 'Tyson' hitting a toddler.
I liked the idea in US, lots of wagons had various warnings on back,one was " this truck takes wide turns"