White Ball of light responds to flashing headlights!

I was on my way to work in the the early morning as I went over the bridge that crosses a river I had noticed a huge white light moving up a little and back down alittle ,like a slow moving bounce. The car in front of me had to of seen it.I have see alot of these objects all my life in my area and so have other people here.As the car in front of me kept going I pulled off the side over the bridge and parked my car as it drifted away from me with no sound. I flashed my head lights at the light and the thing responded to my flashing of head lights.It moved from the left to the right and once it was lined up to my headlights it started to move toward me slowly with a up and down movement, coming closer and closer my heart was pumping as I was about rock throwing distance, In fear of what might happen and what I might experience I backed up my car up and got out of the area fast.I have see so many of these things growing up and its very hard to deal with when you try to tell people and you learn not to say anything!These balls of lights I see are about the size of a small car. I also have see them much larger and in formation moving  up and down by my creek bed then zip across the road into a field and sometimes they zig zag away.I only see them in march to may then again in september to november.
Date is approximate.  PD