The PATH Act modifies how the federal government evaluates whether transit projects deserve federal funding through the fixed guideway capital investment grants program. Currently, the law uses specific formulas to predict how many people will ride new transit systems, but this bill allows transit agencies to use more flexible forecasting methods that account for population density, population growth rates, and local development plans. The legislation is designed to help high-growth communities demonstrate that new transit projects are economically justified, potentially making it easier for rapidly expanding areas to qualify for federal transit grants. The bill affects transit agencies and communities seeking federal funding for rail and bus rapid transit projects. No specific funding amounts or implementation timelines are specified in the legislation.