The Atlantic Cities reported yesterday on a novel study by Metro assessing the impact of, well, just not having Metro. The study produced some interesting, though not wholly unpredictable conclusions.

In a first scenario where Metro disappeared but we had the same road infrastructure we have now, people would just stop driving long distances. (Yay shop local!) In a second scenario, roadway capacity would expand to accommodate all the new drivers, at a cost of $6 billion for the 1,000 lane miles needed. All of those extra drivers would need extra places to park their cars, and that too would come at a cost. According to the study, all the five-story parking garages needed would cover roughly 166 blocks.

There would be other effects, too:

It’s easy to see how the loss of transit could ripple out even further, impacting everything from greenhouse gasses to the city’s green space to its water quality. At that point, this exercise in counterfactuals starts to get really complicated (and beyond the scope of what even Antos could wrap his head around). The point, though, is that transit produces an awful lot of benefits — parking garages deferred, congestion mitigated, jobs created — we don’t think about enough.

While it’s fun — and terrifying — to play around with these hypotheticals, no one should base their existing opinion on Metro solely on the idea that if it weren’t around commuting would suck way worse than it does now. If that were the case, it would certainly say something about how far popular opinion with the region’s mass transit agency has fallen.

Martin Austermuhle blogs at DCist . The Local Blog Network is a group of bloggers from around the D.C. region who have agreed to make regular contributions to All Opinions Are Local.