trick photography

The photo is taken on top of a tunnel, with white cars going in and black cars coming out, no pollution jokes intended. The main idea I had before I took the shot was to capture contrast and motion, which is why I picked vehicles as a subject. I took well over 100 different photographs and I probably used 25 shots to create this one. I think the hardest part was to estimate the positions of the cars and the amount of white and black vehicles. I made it even harder for myself by accidentally moving the tripod ever so slightly during the session, which was quite annoying later in the post processing.
Canon G11, f/3,2, 1/400 sec, ISO 80
-Loui Nydelius
from http://gizmodo.com/#!5643192/30-impossible-scenes-that-actually-happened