In 2017, Governor Charlie Baker toured the Springfield factory where new cars for the Orange and Red lines are to be built. Matthew Cavanaugh for The Boston Globe/File 2017

To Governor Charlie Baker, the MBTA is heading in the “right direction” in updating its aging system. But like passengers on the 111 bus crawling over the Tobin Bridge, many are left asking: Is this as fast as it goes?

The crippling derailment of a Red Line car this week has refueled the debate over how to best fund a transit agency hobbled by years of neglect and decay.

But it’s also laid bare a key difference in how Baker, Democrats, and some business leaders view a solution: As Baker defends his administration’s plans to funnel billions in borrowed money into the T in the coming years, others question the speed, and depth, of the investment as trains derail and a creaky system continues struggling to move people around.

House leaders said Wednesday they’re committed to taking up a tax package in the coming months to fund transportation projects — a need House Speaker Robert A. DeLeo said was “highlighted by recent and unacceptable failures of our transportation system.”

Meanwhile, other elected officials said the T is past the time of tipping points.

“We have to do better, and for him not to understand that it requires deeper financial investment, so that these changes can go into effect faster, is a little bit baffling,” Boston City Council President Andrea J. Campbell said Wednesday of Baker.

MBTA riders have “seen too many either derailments or service outages,” she added. “Now it’s time to act.”

After the winter of 2015 paralyzed the T, Baker all but assumed control of the quasi-public agency, creating a board of his own appointees to oversee and tighten its finances. But he’s rejected calls to raise taxes and inject the system with significant new revenue, saying the T has the money to remold the system.

The $875 million the T spent on capital projects last fiscal year was the most ever, and it’s set a goal of $1.4 billion in capital spending next year. The agency’s planned $8 billion, five-year capital program is, according to Baker, the T’s largest “by a mile,” all with an eye toward cutting down its backlog of repairs by 2032.

Hundreds of new Orange Line and Red Line cars are also in the queue, with the first of 152 new Orange Line cars expected to go into service this summer. The fleet is slated to be replaced by 2022, and Red Line vehicles will start being tested next year, with the goal of swapping out all of that line’s decades-old cars by 2023.

A new $218 million signal system is also slated to be installed on both lines by 2022.

“I do believe we’re moving in the right direction. Infrastructure improvement is at the forefront of every discussion we have,” said Monica Tibbits-Nutt, who sits on the T board.

There are also the logistical limitations to ramping up improvement projects. Beyond hiring enough people for the work, T officials have argued there are only so many hours available between when service ends one day and starts the next. To accelerate the work could mean committing to extended service shutdowns, further affecting the riding public.

“We can’t do everything at once,” MBTA general manager Steve Poftak said. “We are operating a system in a major metropolitan area that is very dependent on the system. We’re operating at all hours.

“I do think it’s important to emphasize that these are not conceptual plans,” he added of the T’s investments. “These are going to result in real tangible progress for the MBTA.”

But even some of the planned improvements have run into problems. The debut of the new Orange Line cars has repeatedly been delayed, and a new automated fare collection system that promises to speed up service is also behind schedule. Last month, the T revised its price tag for fully upgrading the system — known as the state-of-good-repair backlog — from $7.3 billion up to $10 billion.

MBTA fares are also slated to rise by nearly 6 percent on July 1. Add in this week’s delay-inducing derailment, and the frustration among strap-hangers and politicians is palpable.

A change.org petition surfaced Wednesday, calling for a freeze on fare hikes and a federal probe into the T.

“I think we’re long past the point where action is required,” said state Senator Joseph A. Boncore, the Senate chair of the transportation committee. “We are seeing a historic lack of investment really coming to a head and really creating a public distrust in the system.”

Legislators moved toward one potential solution Wednesday by overwhelmingly advancing a constitutional amendment, 147-48, that would impose an additional tax on people making $1 million or more. Revenue from the “millionaires tax” would go toward education and transportation improvements.

The vote, however, is only one step toward the amendment potentially appearing on the 2022 ballot, and if approved by voters, it wouldn’t take effect until 2023.

In a statement, DeLeo framed the plan to tackle “short-term funding” for transportation through a separate tax package this year as a way to buttress what the tax on high earners could ultimately provide.

“Clearly the last week has shown that some form of revenue for transportation projects is needed on a much earlier schedule,” said Representative William M. Straus, the House chairman of the transportation committee. “The seriousness of what we’ve seen . . . calls out for this.”

Senate President Karen E. Spilka said in a statement the Senate is trying to find a “consensus on what must be done and how we pay for it.”

There are many, including in the business community, who say investment in the T’s needs should be accelerated now.

“We’re not approaching this like a crisis,” said Richard A. Dimino, president of the business group A Better City. “We’re not doing a good enough job on the state-of-good-repair. We need to put that effort on steroids.”

Somerville Mayor Joseph A. Curtatone, a Democrat who this week said the “whole system’s been derailed,” said the T has made noticeable progress under Baker, including by putting transportation Secretary Stephanie Pollack and Poftak at the top of the agency.

“We have smart people in place. We have people who get it. What’s bewildering to me is, where’s the sense of urgency?” he said. “I don’t disagree that we’re heading in the right direction. But it’s certainly not at the pace and speed that is needed.”