Chicago police Lt. Richard Plotke steered the bicycle around an obstacle course of eight cones designed to give him an idea of how it will be to maneuver around pedestrians and through narrow gangways.

"I've been riding obviously my whole life, but this is tough. This is very tough training," Plotke said, his voice slightly muffled as he spoke through a gas mask he donned as part of the training. "You've got to know how to ride. You've got to have balance."

Plotke was among the latest class — 16 in all last month — to become one of the department's hundreds of officers trained to patrol on bike.

Bicycle patrols played a key and visible role in keeping thousands of demonstrators in check in the weeks leading up to and during the NATO summit in May. But their work goes on throughout much of the year across the city.

While Chicago police used bicycles before cars became the principal mode of transportation, it wasn't until the early 1990s that the department organized a 20-officer bike patrol on orders of Mayor Richard Daley. For years, their duties were largely confined to the lakefront.

The department closely guards manpower numbers, but shortly before the NATO summit, Superintendent Garry McCarthy revealed at a public briefing that he had doubled the officers assigned full time to the bike patrol.

In addition, hundreds more officers have undergone training to patrol on bikes part time in police districts throughout Chicago.

Sgt. Joseph Andruzzi, who has headed the bike patrol since 1999, said that over the last seven years 100 to 200 officers a year completed the training.

Police sources assigned to the districts said officers patrol on bikes as regularly as possible, but staff shortages have limited their role somewhat.

On a bike, officers enjoy more face-to-face interaction with citizens. And their responsibilities can vary, from working street festivals in the neighborhoods and writing parking tickets to sneaking up on unsuspecting wrongdoers.

Just last week, officers from Andruzzi's unit arrested a juvenile who had a gun on the lakefront path along North Lake Shore Drive, an area not easily accessible by squad cars. The officers' attention was drawn to him when they smelled marijuana while riding by on their bikes, Andruzzi said.

"A police officer on a bicycle is the epitome of curb-to-curb police work," Andruzzi said. "We do everything from handle a simple aggressive panhandler on the corner to a stolen car or a man with a gun (and) everything in between."

Typically the officers dress in uniform — albeit in shorts and with a retractable, not wooden, baton. But sometimes they don plainclothes to blend in for covert or surveillance missions, one police source said. And while they have traditionally been used during warm weather months, patrolling on bikes in the districts has increased in colder weather.

Training for bike patrols started in the mid-1990s with officers undergoing just two hours of instruction. It increased gradually to the current four-day regimen.

Their mettle was put to the test during protests leading up to the NATO summit, particularly the four days around the weekend event.

The bike unit, buttressed by the addition of dozens of officers from districts around the city, weaved through traffic to keep ahead of marchers. They used their two-wheelers to force demonstrators back onto sidewalks and then formed a barrier to keep them from getting back into the street. At times they also used their bikes to block the entrances of downtown banks when protesters tried to force their way into the lobbies.

"We were on the flanks of these crowds in obstacle courses all day," said Officer Grace Delgado, who's assigned to the bike unit. "The first day was 16 hours on bikes. The second and third days were 14 hours. And the fourth day was 12 hours. It was cold one day. It was extremely hot one day. It was a downpour another day."

But ordinarily a six- to seven-hour shift on a bike might entail riding just up to 16 miles, not a lot, according to Andruzzi. The reason, he said, was all the stopping to talk to passersby, write parking tickets and make arrests.

Last month a Tribune reporter was given access to the training that officers undergo before they are allowed to patrol on a bike.

In the parking lot at Whitney Young Magnet High School, the 16 officers stood with their bicycles as their instructor, Officer Julio Guevara, yelled, "Gas! Gas! Gas!" The officers knelt to the ground and quickly unzipped the knapsacks on the side of their duty belts. They pulled out the gas masks, strapped them on and placed their sky-blue riot helmets over their heads.

Seconds later, Guevara exclaimed, "Clear. Clear. All clear," the signal for the officers to take off the gas masks.

Gas masks and riot helmets aren't standard gear, of course, but the officers were being prepared for controlling potentially unruly crowds during protests.

Plotke, a watch commander in the North Side's Town Hall police district who is responsible for a portion of the lakefront as well as the Wrigleyville neighborhood, said the training will help him since he routinely manages crowds at Cubs games and the annual Gay Pride Parade.

"We went on a 16-mile bike ride … in the 97-degree heat with the bulletproof vests on," he said. "It was a challenge."

In another crowd-control exercise, the officers grabbed ahold of their bikes by the seat and handlebars. They then walked slowly and pushed their bikes forward while repeatedly chanting, "Move. Back. Move. Back."

The officers later rode around the parking lot in two rows to form a "V," an exercise designed to force large crowds off the street and onto the sidewalks.

"We kind of go in (as) a street sweeper," Guevara said of the tactic.

jgorner@tribune.com