Scenario editor is (one day) software for editing road networks and scenarios for traffic simulation.
Before getting started you'll need to install git, node.js and npm(npm comes with node.js). Here are instructions for installing node.js as well as reference to installing git: http://howtonode.org/how-to-install-nodejs
Please see the Scenario Edit Wiki (https://github.com/calpath/scenario-editor/wiki) under Build and Run on how to develop with it.