The D.C. transportation department is building a record of partially fulfilled promises on bike lanes, bus lanes, street parking, streetcar service and pedestrian safety.

“In the 12 years since the District Department of Transportation was spun off from the Department of Public Works, no one has asked the critical question: Does the current agency structure work,” D.C. Council member Mary M. Cheh (D-Ward 3) said last week.

Cheh thinks the answer is no. She introduced a bill that would bust up the department and let similar functions cluster together in new agencies.

Parking programs would be consolidated into one agency. All forms of transit, plus for-hire vehicles and the Capital Bikeshare program would be overseen by a new District Transit Authority.

Through community discussions and public hearings, the details may change, she said in a statement, but “the aim is to simplify decision-making and operations.”

For the discussion: While DDOT has flubbed some starts, this is not a record of failure. The department has advanced many progressive programs for transit. A new crosstown bike lane on M Street NW will open soon. Streetcars are coming to H Street and Benning Road NE this year. DDOT did very well on its most ambitious project, the vastly complicated task of rebuilding the 11th Street Bridge over the Anacostia River. In the works is reconstruction of the Douglass Bridge and South Capitol Street.

Some critiques of the department amount to saying it moved too fast, rather than too slowly. That includes the start-up of the red-top street meter program for disabled people, the revamping of the visitor parking permit system, the streetcar line originally planned for Anacostia and last year’s traffic pattern changes on Wisconsin Avenue.

Public dismay — and sometimes, council action — led the department to backtrack. Splitting up the department isn’t the cure for that.

But the biggest issue isn’t the history. It’s the future. A 21st-century view of urban transportation should encompass all modes of getting around. Solutions to our travel problems should be based on moving people, rather than on moving cars, or moving buses or moving bikes or moving pedestrians.

There’s a solid case for having one department oversee melding the modes rather than dividing responsibilities among bureaucracies that might compete for street space.

“This proposal could further balkanize how transportation is done,” said Cheryl Cort, policy director at the Coalition for Smarter Growth. “Over the short history of DDOT, policy and planning have slowly emerged to better guide engineering decisions. However, more needs to be done to put policy and planning in charge of what we build and manage. This bill would be a tremendous setback.

“How to plan and interconnect the ways we travel . . . should be under one agency head,” she said.

We already have issues with the number of agencies responsible for urban transportation. Enhanced bus service provides one of the best hopes for improving commutes within the lifetime of today’s commuters, but that’s not just a question of buying more buses. To attract more riders, the buses need to offer a quicker, more reliable trip than people can get in their cars. That means creating bus-only lanes and giving buses priority at signals.

A key obstacle regionwide: One agency, Metro, controls the buses while the streets are controlled by highway departments. Officials within those bureaucracies don’t necessarily have the same interests.

“Council members do ‘ready, fire, aim’ all the time,” said Richard Layman, author of the blog Rebuilding Place in the Urban Space. DDOT needs to be reviewed and evaluated, he said, but “a unified agency is required, with a solid master plan.”

“Parking functions need to be consolidated, but within DDOT,” he said. “I’d even consider adding the traffic enforcement unit of the police department.”

Spinning off parking functions into their own agency might address the widespread frustration with confusing street signs that don’t match the meters. But, as Layman pointed out, there’s a downside: “A parking agency as Cheh recommends would privilege motor vehicle use of the public space for car storage.”

The city anticipates adding a quarter million residents over the next several decades. Meanwhile, it’s not planning any major addition to its street network. That combination is bad for drivers as well as other travelers, and the answer isn’t to create a separate customer service agency supporting people who want to park.

“Perhaps this is the only tool that the council believes they have to press the administration for a serious assessment of what needs to change,” Cort said of Cheh’s bill. “But it’s not. Let’s have a study commission to diagnose the problems, and identify best practices and recommend solutions.”