Here's my rule for all outdoor photographs...i always expose for the sky, then use flash to lighten foreground subjects. this probably could have helped in this photograph, but it's not a huge problem seeing as you didn't include alot of sky in the photo.
The sun seems to be going down, if you had taken the shot just a little bit earlier when the sun was still on the trucks it would have helped to give them more definition and character. I like the idea of the shot though
Luke