100%, but I only have 4 engines at the moment I have two on the main and two in sidings at all times, and I have room for two more in the sidings. So until I get to six engines, I run them all.
Note that I will probably have more than 6 engines before I know what happened......
Then I'll have to choose or build more trackage.
-Eric
<EDIT> In case I misinterpreted, they are all currently in running condition. Two days ago it was more like 75%. This aspect apparently varies based on my karma any given moment.