A Somerville alderwoman is calling for a review of the effect of road closures during SomerStreets, a series of monthly summer street festivals throughout the city. Rebekah Gewirtz said she supports the events, but she wants to review ways to reduce the impact of road closures as a result of the events. “We’re shutting down the roadways, a lot. . . . ,” Gewirtz said. “I was trying to get from one end of the city to Union Square, and, I’m not kidding, it took me an hour.” A proposed event permit was tabled March 14 to give time for the city to review the road closures.