If DUMB transit uses maglev, then the straight lines of mag rails will be detectable because they stand out from nature's terrestrial fields. If only there were civilian scanning flights somehow, we could suss out the tunnels. For example, we know Denver airport is underlaid with these, so we should be able to start by flying over the airport and then via magnetic field detectors, tracing the lines going from it. One more thing: deep underground tunnels HAVE to be only within tectonic plate boundaries, since crossing a plate border is subject to seismic instability. So I wonder how they handle California's DUMBs. Maybe there are plate-to-plate transfer stations, so we could look along such boundaries for stations; the maglev lines would have discontinuities at these places.

If DUMB transit uses maglev, then the straight lines of mag rails will be detectable because they stand out from nature's terrestrial fields. If only there were civilian scanning flights somehow, we could suss out the tunnels. For example, we know Denver airport is underlaid with these, so we should be able to start by flying over the airport and then via magnetic field detectors, tracing the lines going from it. One more thing: deep underground tunnels HAVE to be only within tectonic plates, since crossing a plate border is seismically unstable. So I wonder how they handle California's DUMBs. Maybe there are plate-to-plate transfer stations, so we could look along such boundaries for stations; the maglev lines would have discontinuities at these places.

If DUMB transit uses maglev, then the straight lines of mag rails will be detectable because they stand out from nature's terrestrial fields. If only there were civilian scanning flights somehow, we could suss out the tunnels. For example, we know Denver airport is underlaid with these, so we should be able to start by flying over the airport and then via magnetic field detectors, tracing the lines going from it.