On many mornings, as commuters pack themselves into subway trains and drivers squeeze onto the streets, Janette Sadik-Khan, the commissioner of the Department of Transportation, rides her bicycle to work.

That the head of an agency long associated with car travel is an avid bicyclist symbolizes what might be a new way of thinking about how New York's asphalt should be used. In recent months, the city has pledged to add bicycle racks and hundreds of miles of bike lanes on city streets and has been exploring a program similar to one in Paris in which people can use bikes at minimal cost.

The Bloomberg administration says it wants to develop cycling as a viable transportation alternative to ease traffic congestion, reduce carbon emissions and encourage physical activity. But the new attention to cycling has also encountered resistance in some neighborhoods, especially when it threatens to remove traffic lanes for cars and trucks.

Ms. Sadik-Khan said her time on two wheels has become an important part of her work.

"It's invaluable to get on a bike and see firsthand the conditions that our projects are trying to address," said Ms. Sadik-Khan, who became the city's transportation commissioner in the spring. "We are really emphasizing connectivity in the bicycle lane network, because all cyclists, myself included, know that it's maddening to be coming along a lane and have it simply end and leave you off on your own on a big avenue."

To that end, the Bloomberg administration has said it will add 200 miles of bike lanes by 2010 - the equivalent of the number added during the last 20 years.

In 2001, the city's Transportation Department tested a light blue bike lane in Downtown Brooklyn and found that in terms of making the lane sufficiently visible to cyclists and drivers alike, it did the trick. But at the urging of the Federal Highway Administration, the department has forgone blue for the Brooklyn Heights bike lane and decided to experiment with green, echoing a growing national movement to make green the official bike lane color.

Other streets are getting paint jobs, too. Last week, in an experiment in making bus lanes more visible, the city laid down coats of terra-cotta-colored paint on bus lanes along part East 57th Street, and it will soon do the same for lanes on Fordham Road in the Bronx.

After the Second Avenue subway finally rolls, it also may eventually bring a new color. The Web site of the Metropolitan Transportation Authority shows a T - the letter tentatively chosen to denote the new line - sitting in a circle of turquoise. (According to Jeremy Soffin, a spokesman, the agency has not yet chosen a permanent color for the circle.)

The choice is of special interest to Lynne Lambert, whose New York City Subway Line is an official licensed maker of subway-themed merchandise. Whatever color is chosen will make its way onto T-shirts, hats and other items Ms. Lambert produces, and she said she would be happy to see the choice on the transportation authority's Web site become permanent.