Are traffic signage locations useful to put onto openstreetmap?

I found a dataset of the latitude and longitude of street signs (stop signs, yeild signs etc.) in the pittsburgh area. Would this be the kind of information that would be useful to the openstreetmap project? It also has lists of speed limits for roads and parking info.

Where is the dataset and do you know under what license its available?

There has been some work, IIRC in Helsinki, of comparing traffic signage with actual on-the-ground mapping (e.g., speed limits). One thing they found was that often signs for restrictions were often incorrectly implemented so the signage did not have the force of law, or was widely inconsistent. So they can be useful, but probably mainly at the point where the relevant informaiton has already been mapped on highway ways.

Again you need to check that the data is truly open. I believe other datasets from Pittsburgh and/or Allegheny County have been used to augment OSM.