Roads
Free riders are able to use roads without paying their taxes because roads are a non-excludable public good.
Source
Boundless vets and curates high-quality, openly licensed content from around the Internet. This particular resource used the following sources:
"All sizes | Construction Traffic on I-376 | Flickr - Photo Sharing!."
http://www.flickr.com/photos/daveynin/3783492242/sizes/o/in/photostream/
Flickr
CC BY.