A top transportation-focused lawmaker wants to hand control of the state’s commuter rail services to the Department of Transportation, a move he says would allow the MBTA to focus on subway and bus service.

Rep. William Straus, a Bristol County Democrat, said it is “fanciful to think” that high-level decisions for the commuter rail are being made by top MBTA officials when Department of Transportation officials have often led the charge for the transit service.

“So why don’t we just end the fiction that the MBTA operates, or makes the key decisions regarding commuter rail? The other policy reason is commuter rail, and daily subway and bus service are very different kinds of operations in terms of how you deploy equipment, and schedule,” said Straus, the co-chair of the Legislature’s Transportation Committee.

The proposal is part of legislation scheduled for a Monday Transportation Committee hearing, where advocates are expected to weigh in on Straus’ bill and others dealing with the commuter rail, MBTA, Western Massachusetts rail service, and East-West rail.

But not everyone is on board with changing up the commuter rail.

“This is a terrible idea,” said Stacy Thompson, executive director of LivableStreets. “… From the goal of trying to get more people onto a seamless transit system, the idea that you would chunk this out and put it under different leadership, just makes it less usable from a very practical perspective. So I just really, truly do not understand."

Ever since Robinson Lalin was dragged to his death by a Red Line train last year, which in part prompted a federal safety inspection of the MBTA, the agency has been grappling with slowed-down trains, dangerous safety failures, and increased public scrutiny.

The Federal Transit Administration issued a lengthy list of mandates aimed at fixing safety problems at the MBTA last summer, and T officials have been working to comply with those.

And the Healey administration has reworked top leadership at the agency — installing new general manager Phillip Eng as well as new MBTA Board of Directors members, and hiring a chief safety officer reporting both to the secretary of transportation and to Eng.

But Straus says the transit agency has too broad of a mandate.

“The approach here is to end up with an MBTA which is smaller in scope, in terms of its responsibilities, so that it can focus on what really, to me, should be its core mission of Boston subway service in the immediate metro area, in a safe, reliable and efficient manner,” Straus said.

Splitting off the commuter rail from the MBTA could affect the ease at which people can transfer to subway or bus services, said Brian Kane, executive director of the MBTA  Advisory Board.

“I just don’t think it makes sense to have another public transportation entity operate that so that you couldn’t have things like transfers to the bus system in places like Newton, or to the Orange Line in places like Oak Grove, or Forest Hills or Quincy,” Kane told the Herald. “To me, making it easier to transfer is where we should be headed.”

Another provision in the bill would convene a group of stakeholders to come up with a plan to transfer safety oversight of the MBTA from the Department of Public Utilities to the Office of the Inspector General.

Inspector General Jeffrey Shapiro is expected to testify on the matter during the Monday hearing, Straus told the Herald.

Thompson said another idea is to create an independent commission to oversee safety at the MBTA similar to the Massachusetts Gaming Commission or the Cannabis Control Commission.

“Maura Healy hired a really good safety officer,” Thompson said. “It’s great that she hired really wonderful DPU commissioners, but it doesn’t solve this core problem of independent oversight that we have models of in the state and that the federal government is encouraging us to do.”

Straus said he is open to changing the bill after he listens to testimony on Monday.

“There isn’t one answer to the T’s problems. We could give them all the money in the world, but if they’re inefficient and don’t manage themselves, or aren’t managed well, we haven’t solved anything,” he said.