You want to argue that an oil-based transportation sector is at an end. Good enough. Forgetting whether you are right or wrong about this for the moment, you want to then proceed with an analysis of current conditions and anticipate future ones by positing a "what-if" with regard to that change.
It doesn't work that way. A simple example: once upon a time, there were no computer or mechanical phone systems. Every call had to be routed through operators, at every level. Every message had to be written down by human hands. And every message had to be delivered or picked up by human agency. These things changed. How many man-hours were used doing these things, prior to such change? How many jobs disappeared, after the change? But that doesn't represent a permanent change in labor distribution. It doesn't mean that there is no some percentage of the labor force out of work, for ever and always. Yet, you seem to think that is the way it works.
A change in the transportation sector--whatever the cause--will certainly affect many, IN THE MOMENT. But it is wrong-headed to 1) predict the exact extent of such, 2) assume the effect is permanent, and 3) assume what the immediate consequences will be, barring any evidence of such.
You are engaging in wild speculation on a number of levels.
I get that you are researching "peak oil," that you may very well understand many things about this topic. But you should be careful when you use such understanding to derive opinions on the consequences. I can say the same thing to many global-warming alarmist, scientist and lay-man alike, who suppose they know the consequences for the economy.
Economics is not--imo--a science. Not yet, anyway. It is, however, a very difficult field. To suppose one can have predicative power--long and short term--within it is, frankly, nonsensical.