Arrest or not arrest?

I observed this pickup truck transporting a load of wood pallets, illegaly. the pallets were not securely fastened to the vehicle, as required by law. as i approached the vehicle, i noticed the driver was an elderly man. i asked to see his drivers license and proof of insurance. the driver immediately open the trucks door and began urinating on the side of his truck. i did not smell the odor of alcohol. the driver did say, “excuse me, i have to go”. this had never occured to me before on a traffic stop, so i was a little shocked. the driver finished and said, “i take a water pill and i have to go often”. i issued him a citation for expired drivers license, but should i have also arrested him for indecent exposure?