Do you want all the costs of a metro system with none of the speeds or connectivity. Do you just want to build something to shut up the transit advocates without addressing the issues with car dependence in your city. Try a streetcar system. They could be useful but we know that you over at [insert American city here] don't care about good transit, you want to use transit as a tool of economic development. And we can garentee that it might maybe boost the economy in a way more noticable than the displacement it could cause. It worked as transit for literally just Portland and Kansas city and isn't that enough? Maybe your city will be the 3rd US city with a good modern streetcar