Several transportation advocacy groups, frustrated with what they call the city’s consistent stalling on major transit policy changes, want to alter the way the city measures traffic congestion and road performance.

The Department of Transportation determines street performance by measuring the number of vehicles that pass through a street block in a period of time.

The advocates want a more detailed system, where the type of vehicle is taken into consideration. Thus, a bus full of people would not be counted as equal to an SUV cruising along with a driver and no passengers.

The chairman of the City Council’s Transportation Committee, John Liu, said the committee may hold a public hearing this year on the possibility of using the new system of measuring street performance.

“The issue is not limiting the numbers of trucks or any particular vehicles, but maximizing the utilization of scarce street resources,” he said.

One of the groups, Transportation Alternatives, blames Mayor Bloomberg’s reluctance to embrace radical changes such as congestion pricing in part on the Department of Transportation’s “outdated metrics that keep planners focused on moving motor vehicles and not enough on the City’s full range of transportation options,” according to an article to be published this week in the group’s newsletter.

A spokesman for the Department of Transportation, Chris Gilbride, said the department occasionally conducts surveys, with staff members counting and categorizing traffic on street corners, but because resources are limited it relies mostly on automatic traffic recorders.

The head of Transportation Alternatives, Paul Steely White, said New York City has a lot to learn from the City of London. While Londoners are making strides in reducing vehicular traffic without hurting commerce or commuters, New York is worrying about less important goals, he said.

“Potholes filled and streetlights repaired are important, but the DOT should be measuring success in smarter ways,” he said. His organization has a menu of changes it would like to see the city aim for, including reductions in weekday traffic and bus wait times.

The new system would break down the way people move about in the city into different categories, allowing for policy makers to shape their plans around “modal targets.” Transportation Alternatives wants the city to reduce driving into Manhattan’s central business district by 10% and increase walking and biking by 10%. Subtracting from one part of a pie graph allows additions in other parts so that overall the number of people making trips into the area doesn’t decrease, Mr. White said.