STOPS is a limited implementation of the conventional "4-step" travel model developed by the Federal Transit Administration (FTA).
STOPS replaces the standard "trip generation" and "trip distribution" steps with the Census Transportation Planning Package (CTPP)
tabulations from the 2000 census to describe overall travel markets. It also replaces the traditional "coded" transit network with
standard transit services data in the General Transit Feed Specification (GTFS) format.
RTA has led an effort to establish a consistent set of inputs to represent a "base case" scenario for the entire RTA region
within the STOPS environment. From this base scenario, transit modelers should be able to code new build and no-build scenarios
with a significant reduction in setup and calibration time. By using a consistent set of model inputs for the entire region and
coding new projects in line with the Chicago Region User Guide, RTA hopes to allow transit operators, planners, and advocacy groups
to explore transit improvements in a manner that produces reliable estimates across the Chicago region.