Rochester NY tried the same thing, with roughly the same results. It's a shame the technology and need for public transit correlated with the automobile explosion, but culture drives society - if people in either Rochester or Cincinatri or anywhere else with a defunct subway project really wanted it completed, it would have been done. Now the fashion is urban density, and cars are increasingly seen as a blight on walkable downtowns. At least Cincinatti's regular tunnel upkeep gives the people the chance to dream.