Will go a step further than ATV's. On our club we have a lot of gas well roads - so our deer are familiar with trucks being in/out regularly. Yesterday, I was watching a mature buck in a food plot when a guy drove in one ridge over from me. From the time the guy left the gate off the main road, the buck grew more and more tense - and finally bolted out of the plot when the truck was about "equal level" on that ridge to our ridge. Didn't totally bust with blowing and "scramming"... but quickly turned and loped out of the plot.