It seems better to use a hyphen (-) to separate words in the URL.

It seems that it is better to use hyphens (-) rather than underscores (_) to separate words in URLs.

It is useful to use delimiters in URLs. The URL http://www.example.com/green-dress.html is much more understandable than the URL http://www.example.com/greendress.html. We recommend using hyphens (-) instead of underscores (_) in URLs.

via: Keep a simple URL structure - Webmaster Tools Help

Yeah, yeah, seriously...

This is Google's official opinion, but I wish I had known it sooner...

Now, let's fix the URL...