Okay, you gave a good portion of information, but you should make the stages you mention clearer by punctuating them, for instance:
-Stage one:
-Stage two:
-Stage three:
-As many stages as you like.
Another thing you could do add subtitles and others to make it cleaner and easier for the reader to jump straight to what they want to see. I usually jump to said subtitles when reading other SCP-files because i'm for example not that interested in containment procedures.
Otherwise i absolutely LOVE the concept, something that could happen to everyone, i.e. creepypasty, simple but unsettling enough. Develop more things this SCP does and you might creep any readers when riding any vehicle.
Lordeaglemeagle