From the homepage:
Welcome to SCAG’s Bike Ped Planning Page.
This site is a new approach to public involvement in transportation planning. Rather than the traditional approach of public review and comment, you are now part of the planning process itself. […]
The results will be considered by SCAG for incorporation into the Regional Transportation Plan (RTP) in summer 2011, which looks at the transportation infrastructure needed to meet the needs of Southern Californians 20+ years into the future. But this Wiki will not stop then. It will continue to evolve, serve as a resource for stakeholders and local governments, and be used for the 2016 RTP update (Release 2.0).
From the about page:
SCAG is the nation’s largest metropolitan planning organization, representing six counties, including Imperial, Los Angeles, Riverside, San Bernardino and Ventura Counties. In addition, SCAG represents 190 cities and more than 19 million residents. SCAG undertakes a variety of planning and policy initiatives to encourage a more sustainable Southern California now and in the future.
The site is produced by Melbourne, Australia-based Collabforge.
From the source code, it appears the site runs on Drupal.