The mission of the Ann Arbor Downtown Development Authority (DDA) is to undertake public improvements that have the greatest impact in strengthening the downtown area and attracting new private investments. Since 1982, the Ann Arbor DDA has done a great deal to improve the attractiveness, walkability, and vitality of downtown. It emphasizes infrastructure projects including constructing parking structures and installing transformative streetscapes, but also works on a variety of smaller projects in support of its mission, including providing free bus passes for downtown employees, installing bike parking, and grants to encourage the creation of new workforce housing units. The Ann Arbor DDA District encompasses all or part of 67 city blocks, or approximately 271 acres. Of this total, 80 acres are public rights-of-way, 72 acres are in public use, 42 acres contain UM properties, and approximately 1/3 of the DDA District is contained within an historic district. The work of the DDA is done by a small staff and a Board of twelve citizens appointed by the Mayor and City Council. DDA members volunteer their time, talent, and expertise to the DDA for the benefit of the downtown. They serve four-year terms and work through committees to accomplish the goals of the DDA.