No you're a frustrated engineer because you don't drive trains, and that's what engineers are supposed to do!!!
JK... I'm the same way. I have to analyze everything to death, and even then I'm not sure.
You could do a FMECA and figure out the statistical probability of what your prime failures will be given each method. That will at least make you be able to sleep at night knowing you did your due diligence and are not a slacker for and engineer...
You can also derive a fault tree from your primary requirements list. Just don't include double or multiple fault scenarios. Only do single credible faults and you should come out o.k.
Rocketman....
and for those wondering what FMECA is ...
Failure mode, effects, and criticality analysis - Wikipedia, the free encyclopedia