Waze carpool launched ~2Y ago in Israel. I've been a registered driver/passenger for about a year now. Here's my summary:

  - I don't like the fact it's a separate app rather than part of waze.
  - Apparently matching rides is technically non-trivial. I was hit with so many false positives I could not cope and had to deregister (as a driver).
  - Car sharing is culturally challenging, even in Israel. I guess more so in the US.
  - This will no work.