It was big! It looked the size of the moon in a perspective visual comparison. It was fast dropping straight down in front of me and then it vanished before it even got low enough to disappear at the horizon point. I hope more than anything someone else caught this and has photos or video evidence, it was such an amazing experience! I may not be 100% accurate on time and exact location as it was a very dark highway and I was freaking out for a few minutes after seeing it but I hope it was close enough that it matches other sightings reported. There is no possible way I was the only witness.