...Standard & Poor's Ratings Services assigned its '##+' rating to Ann Arbor, Mich.'s series 2015 general obligation (GO) limited-tax open space preservation refunding bonds. At the same time, we affirmed our '##+' ratings on the city's outstanding GO bonds. The outlook is stable. The bonds are secured by a statutory first lien on a half-mill levy approved by voters in November 2003 for acquiring land and land rights. However, the rating is based on the city's full faith and credit limited-tax GO pledge, which we view as the stronger security. The city plans to use bond proceeds to refund it series 2005 limited-tax GO open space preservation bonds for expected interest cost savings. The '##+' rating reflects our assessment of the following factors for the city, specifically its:...