bright light hoovering along car at slow speed on foggy nite

I was returning from Pine Bluff Arkansas early in the morning.I had taken the back route which is HWY 15 which has a long straight section of highway about 7 miles in length.It was very foggy and I was driving a 1980 Monte Carlo at about 25 miles per hour.I noticed a bright light behind me that seemed to be elevated.It approached very fast. I thought it was a 18 wheeler taking a short cut to avoid the the weigh station so I started to pump the brakes to let him know I was in front of him.The light came right up on rear as I continued to pump the brakes.I noticed that the light was to high to be a big truck, about that time it passed over the car at about telephone pole height.By this time I had slowed to about 10 mile per hour and had rolled down the window.The brightness hoovered above the car for about 5 seconds then moved forward.There was no sound from the brightness in front of me.Then the brightness moved to the left of the highway and traveled along side of me at about 10 miles per hour for about 15 second then dissapeared.The whole incident lasted maybe a minute an a half.
The date may be approximate.  PD