Mayor Rahm Emanuel's plan to install 100 miles of protected bicycle lanes in Chicago by 2015 is running into a speed bump thrown down by the state.

Streets where the Chicago Department of Transportation has installed or plans to build protected bike lanes include Jackson Boulevard, Clybourn Avenue, Diversey Avenue, Elston Avenue, Washington Boulevard, Adams Street, Archer Avenue and Pershing Road.

The protected lanes are designed to improve safety for cyclists by creating a physical barrier — a parking lane or flexible posts — between moving vehicles and bikes.

But in many of the selected locations, sections of the roadways fall under state jurisdiction. The Illinois Department of Transportation won't allow protected bicycle lanes to go on state-designated routes until it is satisfied they are safe, officials said.

IDOT will collect at least three years' worth of traffic accident data and then make a determination based on the analysis, officials said, adding that the existing information is inadequate because protected bike lanes are new here.

"We don't want to make decisions on a scattershot basis. Our traffic engineers want to see more data on the impact of protected bike lanes,'' IDOT spokesman Mike Claffey said.

Claffey said IDOT has safety concerns that include the visibility of cyclists at intersections and operational issues like maintenance and snow-removal around protected bike lanes. Approving protected bike lanes for Chicago would open the floodgates to allowing all other local governments in the state to do the same, he said.

"We are also concerned about losing traffic lanes,'' Claffey said, noting that protected bike lanes require more space than traditional bike lanes.

IDOT's go-slow approach may win applause from some drivers who think Chicago is going overboard, especially on such thoroughfares as Dearborn Street downtown, where critics say a new configuration with two-way protected bike lanes makes traffic nearly immovable and dangerous for pedestrians.

But some transportation professionals say IDOT should let Chicago move forward with its plan.

"With about 60 traffic crashes every day in Chicago that result in injuries and fatalities, why would IDOT put the brakes on a proven traffic safety strategy?" said Ron Burke, executive director of the Active Transportation Alliance, which promotes greater use of alternative transportation.

"Chicagoans want safer streets, and studies show that protected bike lanes create more order on the streets and reduce injuries involving bikes, pedestrians and cars," Burke said.

Steven Vance, a transportation planner who is a bicycling advocate, said IDOT's action is unwarranted because there is ample evidence from cities worldwide pointing to the safety benefits of protected bike lanes in reducing crashes.

New York City's protected bike lane on 9th Avenue led to a 56 percent reduction in injuries to all street users, including a 29 percent reduction in injuries to people walking, according to the city's transportation department.

"IDOT is being a little stubborn,'' said Vance, 28, who is deputy editor of Streetsblog Chicago, which covers sustainable transportation issues. He was first to blog about IDOT's policy imposing a "moratorium'' on the city's installation of protected bike lanes.

"IDOT says the safety performance of protected bike lanes is inconclusive, but there is a lot of information showing that the farther you can get a cyclist away from cars, the safer that cyclist will be,'' Vance said in an interview.

"I am concerned that IDOT will continue to find the data inconclusive. It seems IDOT doesn't want to be 100 percent pro-car (any longer), but they are having a difficult time making the transition.''

Claffey disagreed. IDOT revised its policies under the state's Complete Streets program approved by the General Assembly and signed into law by Gov. Pat Quinn three years ago, he said. As an example, he said, IDOT now pays 80 percent of the cost for localities to construct new bike lanes during road projects, compared with no state match previously.

Chicago's first protected bike lane was completed in July 2011 on a half-mile stretch of Kinzie Street between Milwaukee Avenue and Wells Street, so IDOT will continue to collect crash reports through at least half of 2014, officials said.

For the short term, it means there will be a patchwork of bike-vehicle separations on the streets that, some argue, could lead to confusion among cyclists and motorists and possibly cause or contribute to accidents.

On Jackson, the barrier-protected bike lane starts at Western Avenue, but it switches at Ogden Avenue to a buffered bike lane. The reason for the change is that Jackson is a state route between Ogden and Lake Shore Drive.

A buffered bike lane uses pavement markings to create more spacing than a typical bike lane provides between motorized traffic and bikes, but the buffered space lacks a physical barrier to protect cyclists from vehicles.

The buffered lane extends east on Jackson from Ogden to Halsted Street, except for a one-block stretch of Jackson between Ashland Avenue and Laflin Street where the road narrows. There are no bike lanes on Jackson east of Halsted.

A bike lane designated for cyclists on Jackson is needed in the downtown, from Halsted past Union Station and the Financial District through to Wabash Avenue, Vance said.

CDOT officials, meanwhile, are following IDOT's marching orders.

"We are monitoring traffic operations on roadways with recently installed protected bike lanes. As these analyses progress, we will share our findings with IDOT and work together to develop a strategy for the installation of these innovative facilities on state jurisdiction roadways,'' CDOT said in a statement.

Emanuel will undoubtedly push ahead with his plan to build 100 miles of bike lanes in his first term, Vance said, but the city may be forced by the IDOT delay to "put something in that is less desirable by the community, like a buffered bike lane," he said.

CDOT recently changed its terminology to reclassify buffered bike lanes as "buffer-protected bike lanes.'' But Vance said it is "disingenuous to say that a painted buffer is a kind of barrier; just ask any bicycling mom.''

Contact Getting Around at jhilkevitch@tribune.com or c/o the Chicago Tribune, 435 N. Michigan Ave., Chicago, IL 60611; on Twitter @jhilkevitch; and at facebook.com/jhilkevitch. Read recent columns atchicagotribune.com/gettingaround.