Is that photoshopped together? It looks really weird, since the cars are obviously toy cars (Hot Wheels sort of thing), and the fireworks look almost hand-drawn.
I don't think the cars had to be "real" in order to meet this challenge.. very creative of you to think to use toy cars! :) However, they aren't in focus, which really detracts.
The cars not being clear is the first thing I notice about this. The fact that I don't think they are real cars is the second strike. The third strike is that the "fireworks" look more like sparklers to me. Honestly you've almost pulled it off. I would've opted out of the cars if the challenge were not transportation. The fireworks have some appeal as is.