Way too much contrast. Composition is good, not too much problem there, what would have made this shot stronger is using more color variety and allowing your camera to take in more color.
The roller coaster track looks really cool. The track itself sillouhetted and the color of the sky actually take my attention away from the coaster cars. I didn't realize they were on the loop until I'd seen the picture 3 times. The white glare also distracts my attention somewhat. Not sure how well this fits in the 'vehicles' challenge, but I see definately see the intent and I'm not basing my score on that. Overall a great shot.
This is a very nice shot - everything is a sillhouette- crazy lines going here and there, the people suspended vertically and - you even got the moon in the center of it all. Very nice shot indeed. Great timing and great angle. Everything seems in place.