This is the full version, it does not require anything but the base game Train Simulator 2016 to run.
Read more here:
Train-Simulator.com Store Page for the Springfield Line
You can also download and read the full manual there.
Or go directly to the Steam Store page here.
Important Information for Owners of the Springfield Line 1.0 or 2.0
We are still working on the content update from an earlier version of the route to the new, final one. We regret the delays, there have been several unexpected issues close to the release that have forced us to start rebuilding the update package. It should not take us more than a few days, we kindly thank you for your patience. As previously announced, we will inform you here and directly via email when the update is available.