“Let me tell you something,” she told Transportation Secretary Richard A. Davey. “I am so upset with Number 28.”

She meant the bus route between Ruggles and Mattapan, which she boarded just after 5 p.m. at Roxbury Community College, to reach the meeting 4½ miles away at Mattapan’s branch library. “It took an hour and 15 minutes to get here,” she said, narrowing her eyes.

Davey apologized, promising to look into it. But even when the 28 runs on schedule, it covers that stretch in 40 minutes, averaging less than 7 miles an hour — a halting trip of red lights and one-by-one boardings.

That daily reality is at the heart of a set of statistics released last week highlighting a racial disparity that planners, activists, and officials considered at once shocking but not surprising.

Among Greater Boston workers, white commuters who drive have the shortest trips to work — averaging less than 27 minutes each way — and black bus riders the longest, exceeding 46 minutes each way. But a gap exists even among those who take the same mode, with shorter commutes for white workers whether they drive or ride mass transit.

The biggest gap is by bus. Black commuters spend an extra 66 hours a year waiting, riding, and transferring than white bus riders, according to a new analysis from Northeastern University’s Dukakis Center for Urban and Regional Policy .

The Dukakis Center did not look directly at income and lacks hard data for Latino commuters, because the US Census considers Hispanic origin an overlapping ethnicity and not a race. But the center’s associate director, Stephanie Pollack, called the results “a reflection of the affordability of the region.”

In other words, affordable housing is scarce and often far from desirable subway and rail stations. Those who can afford to drive largely do so, because it is faster. And a transit system built up over a century to funnel commuters toward downtown Boston does a poorer job connecting to the service and physical-labor jobs not concentrated downtown — meaning longer, slower bus rides, often with transfers.

“If we care about equity in our transportation system, we have to pay attention to the bus system, which serves so many low-income and people of color,” Pollack said. “We have to do better.”

Lawmakers and advocates see an opportunity in the new year, with Beacon Hill expected to debate new taxes to support the Massachusetts Bay Transportation Authority, the highway system, and the regional bus agencies beyond Greater Boston, a transportation network deeply indebted and unable to keep up with basic maintenance and operations.

But balancing the transportation budgets should not be the only measure of success, said Pollack, which is why the Dukakis Center is calculating statistics to define and track goals such as environmental sustainability and social equity.

“We want a system where nobody’s commute is longer because of the color of their skin,” she said. “What would it take to create that system?”

Davey said the new analysis underscores what he heard while serving as MBTA general manager and now as transportation secretary.

“It doesn’t surprise me,” he said, “but it is another reminder of the hard work we have ahead of us, which is to make sure we’re not leaving anybody behind.”

State Senator Sonia Chang-Diaz, a Jamaica Plain Democrat whose heavily black and Latino district includes Roxbury and parts of Dorchester and Mattapan, said the Dukakis Center has established “metrics to make clear and put on paper the realities that I know and see so many constituents grappling with every day.”

The commuting times, calculated from data collected between 2005 and 2009 through the US Census’s American Community Survey, mean black workers spend an average of 80 more minutes a week than their white counterparts navigating the bus system.

“That’s easily a parent-teacher conference, or time to get your household finances in order,” Chang-Diaz said. “That is a very stark reality for people.”

With lawmakers poised to debate transportation finance, the report “pushes us to think more broadly about what it is we want and need to do about our transportation infrastructure, not just how do we plug this hole,” she said.