Well, yes and no. Within the foreseeable future, we'll have to replace the entire car fleet and petroleum support infrastructure anyway, just to retain current capacity. So the decision is not between doing maintenance on existing infrastructure versus building a new system, but between which new system to build in order to handle any given transportation task.

Even if this were not the case, the case for an upgrade to the infrastructure that results in lower resource use for the same service would depend on your planning horizon. If the service cost, including depreciation, is lower for the new mode than the old mode, then there exists a discount rate for which an upgrade is viable.

Finally, it is possible to have growth in terms of the quality of service rather than in terms of the number of ton- or passenger-kilometers travelled. Rail offers a number of advantages over airplanes and cars - they are more comfortable than either; unlike planes, you don't have to go through a gauntlet of goons to get on; and unlike cars you're not driving yourself, so you can use the time for more interesting pursuits.

- Jake

Friends come and go. Enemies accumulate.