The Chicago-based nonprofit Center for Neighborhood Technology recently unveiled its AllTransit Gap Finder—an online mapping tool designed to point out areas with “inadequate” transit service. It’s a good effort, and it’s certainly good that we have more tools for understanding transit demand.

But the concept of “transit gaps” (or even worse, “transit deserts”) is less enlightening than it seems, for two reasons. First, it ignores the cost of providing transit, which has to be considered when act…