(not a sand-pitter) I got hit once. During walk around, past the outflow valve of the very light Airbus twin, walking half sideways, half backwards below the THS. The waste truck was reversing under the servicing panel. Last time I checked my 6 it was not there. I'm sure driver would say the same about me.
The experience instantly removed all my resentments to the (then new) rule of wearing the hi-viz.