A new report by A Better City calls for $50 billion of investment into the state's transportation system, and outlines a policy framework to upgrade and encourage a modern rail and bus system that will bring people to the infrastructure and get them out of their cars.

Meanwhile, Gov. Charlie Baker has proposed an $18 billion transportation bond bill.

Transportation experts Jim Aloisi and Chris Dempsey joined Boston Public Radio on Tuesday to break down the different proposals.

"The $18 billion bond bill is Gov. Baker's effort to say, 'Here's how we want to spend money that is already coming in.' It's not new money, with the exception of this [Transportation and Climate Initiative] program," said Dempsey, director of Transportation for Massachusetts and former assistant transportation secretary.

"It's essentially a status quo bill," he said. "The $50 billion number is an effort by business groups and others ... to say, 'We think we need a bolder plan, the status quo isn't working,' and it's an attempt to put a price tag on that. ... It might be the right number, it might be the wrong number, but $18 billion is definitely not sufficient to have the transportation system we know we all want.'

Aloisi, former transportation secretary and Commonwealth Magazine contributor, said the $50 billion plan would raise new revenue to get a more robust, sustainable, and modern transportation system.

"It buys resilience, it buys a regional rail system that is a modern, efficient system that runs frequently, all day with clean electric locomotives," Aloisi said.