What are some of the practical obstacles to a “shared interests” between a freight railway business and the proposed new higher speed passenger entity? This paper discusses the real “tension” between the two business interests that fund freight trains versus those that support and fund higher speed passenger trains as they attempt to share the same tracks in a safe manner. There are fundamental laws of physics that have to be addressed as the two different sets of equipment are “accommodated” on a shared corridor. This may not always be an easy accommodation between the two commercial parties. One real tension between the two commercial interests involves the physical problem of accommodating two radically different train sets on areas of curved track. For one example, what will be the passenger train required future higher speeds and how will these speeds be accommodated in existing main line tracks with curves varying from 1% to 6% in degrees? How much super elevation will need to be put back into the heretofore freight train tracks? How will the resulting super elevation affect the operation of so called drag or high tonnage slow speed bulk cargo trains? Accommodating such differences in train set types, axle loadings, freight versus passenger train set speeds, requires making detailed choices at the engineering level. These may be shared interests, but they are also variables with far different outcomes by design for the two different business types. The freight railways have spent the last few decades “taking the super elevation out” because it is not needed for the modern and highly efficient freight trains. Now the requirements of the passenger trains may need for it to be replaced. What are the dynamics and fundamental engineering principles at work here? Grade crossings have a safety issue set of interests that likely require such things as “quad” gates and for the highest passenger train speeds even complete grade separation. Track accommodating very high speed passenger trains requires under federal regulations much closer physical property tolerances in gauge width, track alignment, and surface profile. This in turn increases the level of track inspection and track maintenance expenses versus the standard freight operations in a corridor. Fundamentally, how is this all going to be allocated to the two different commercial train users? What will be the equally shared cost and what are examples of the solely allocated costs when a corridor has such different train users? In summary, this paper provides a description of these shared issues and the fundamental trade-offs that the parties must agree upon related to overall track design, track geometry, track curvature, super elevation options, allowed speeds in curves, more robust protection at grade crossings, and the manner in which these changes from the freight only corridors are to be allocated given the resulting much higher track maintenance costs of these to be shared assets.