Chicago Transportation Commissioner Gabe Klein, best known for bringing bicycle-sharing and speed-enforcement cameras to the city and promoting alternative transit over vehicle travel, is resigning, effective at the end of the month, Klein told the Tribune on Friday.



Klein, 42, said he will return to the private sector, which was part of his original plan when Mayor Rahm Emanuel appointed him to head the Chicago Department of Transportation in May 2011.



Klein and his wife, Stephanie Plummer, who works for the U.S. Environmental Protection Agency in Washington and spends part of each week in Chicago, also plan to start a family soon, he said.



"One of the hardest things for me is leaving because we have been so successful, but I've got some family obligations,'' Klein said in an interview.



Major accomplishments he cited under his 2 ½-year watch include expansion of the Chicago Riverwalk, the start of the Bloomingdale Trail and reducing the repaving cycle for arterial streets to 15 years from 64 years.



Klein has overseen the creation of the Divvy bike-sharing program, which started in late June and has grown to about 3,000 bicycles at some 300 bike-docking stations. The program's implementation was delayed, but bike-sharing is growing in popularity here. Divvy has provided more than 600,000 trips and logged more than 1.5 million miles, city officials said.



Klein did spark controversy over the contract that Chicago awarded to Alta Bicycle Share Inc. to run the bike-sharing program. A rival bidder claimed that Klein, who once did consulting work for Alta, tainted the selection process by failing to disclose the past business relationship. Klein said he recused himself from the process that picked Alta.



Klein said that as a youth, he worked at his parents' bicycle stores in the East, and he singled out the Divvy program as one of his proudest accomplishments.



"Every time I see a Divvy bike or a wider sidewalk or a speed camera slowing drivers down, I know I've had an impact on people's lives,'' he said.



He called being commissioner of transportation in the transportation hub of the United States "the hardest and most rewarding thing I have ever done.''



Before coming to Chicago, Klein was director of the Washington, D.C., Department of Transportation, where he was involved in the development of the district's bike-sharing and trolley bus programs.



He co-founded On The Fly, an electric vehicle vending company, according to a bio of Klein on the CDOT website.



Klein also managed daily operations for bicycle retailer Bikes USA, and oversaw the car-sharing system in the D.C. area when he was regional vice president of Zipcar, the CDOT bio said.



After leaving CDOT, Klein said he plans to take his wife on a vacation, then go to work on developing a couple of private-sector business plans that promote transportation technology.



jhilkevitch@tribune.com



Twitter @jhilkevitch