^^ yeah, I know certain newer systems like Montreal's have the track slope up slightly on the approach to stations, so gravity can assist with braking and acceleration.
Anyway, the more I think about this, the more it sounds like it will exceed Related's budget. Certainly this should cost more than $100M, especially if prevailing wage is required and costly mitigation is needed for Dearborn Park residents. Maybe CTA should just buy out that whole block of 15th.