It doesn't work at the moment - you need to re-upload, and leave the description fields blank, then it should be ok. (It is because of a Greenfoot bug).

Ok, I found out the problem - it's a greenfoot bug that means scenarios with a more-than-one-line description don't work. Fortunately I can fix it after it's been upload.

It doesn't work for me either. Cowbomber, the most likely cause is that it needs files (image/sounds) that aren't inside the project and so aren't included in the export. If you need help getting it to work on the gallery, please send an email to the greenfoot-discuss mailing list (check out greenfoot web page to find it).

I think this is one of the best user-contributed scenarios so far. Well done! There is some room for imnprovement of course - making sure the cars always face in the right direction would be a good start.