I've never done it but I've heard of a path between DTD and Old Key West and was wondering how good it would be to run.I know it's gotta be about 1000x safer than running International Drive.
It's a great path, though one where you should be closer to light than dark. Since the treehouses have reopened, the path is lit all the way to the treehouse bridge (from DTD). Between there and OKW it is dark.
If you are running in the dark, you should use a little caution as you approach the bridges. The pathway has a hill at the bridge to blend into the slope up the bridges. Also, early morning, this path is used heavily by golf course crews. If you see lights coming around a corner, pull off until they see you.
Other than that, it is a great run. There is water at the point where the practice green is located and water at all OKW pools. You can also combine the loops into the Treehouses and through SSR for more miles.
One of the neat things, if you do decide to run in the early hours... The DTD music system is cued up with motion sensors. There used to be a spot in DTD where you would hear the music magically appear.
Here is a loop through OKW and DTD
http://www.mapmyrun.com/routes/fullscreen/164105730/
One with SSR
http://www.mapmyrun.com/routes/fullscreen/5375436/
If you are driving over, the Boardwalk DHS loop is a better run in the early hours. One really needs to try to hit the guard shack at BWV about 0500 or later. They tend to want to turn you around if you are earlier due to safety issues (I have been warned a few times but always allowed in). Tell them you want to run, show your License and tell them you plan to park behind the guard shack. I find if I act like I know what I am doing and have done it before, they rarely give any grief.
Here is the trail
http://www.mapmyrun.com/routes/fullscreen/178482598/