That legislation, the 2012 Moving Ahead for Progress in the 21st Century (MAP-21) bill, is spending about $54 billion per year on road and transit projects across the country.
The traditional source of funding for congressional Transportation bills is the 18.4 cents-per-gallon tax on gasoline purchases that are made by drivers. However, the federal gas tax only brings approximately $35 billion per year.
Boxer said on Thursday that it was important to discuss the transportation funding shortfall "as the president goes on a jobs tour around the country," referring to a series of speeches President Obama is giving this week about his economic proposals.
"If we don't do the right thing and get that highway trust fund up and running, we will lose three million jobs nationwide," Boxer said.
"It's two million with a basic highway bill, and one million with the TIFIA, which as you know is a highly leveraged program that we had a hearing on yesterday in this very room," she continued, making a reference to the Transportation Infrastructure Finance and Innovation Act (TIFIA) loan grant program that was boosted in the 2012 transportation bill.
Boxer said lawmakers have grappled with the shortfall in transportation funding that has been caused by dwindling gas tax revenue before.
"We had funding problems then, and we have funding problems now," Boxer said, referencing the drafting of the 2012 bill.
"We have to figure out a way to fill that trust fund so that it can continue its traditions in history of making sure we have a sufficient infrastructure," Boxer continued.
Some transportation observers have attributed the reduction in gas tax revenues to increases in fuel efficiency for cars. Others have pointed to reduced travel and cargo shipping during lean economic years that have followed the 2008 recession.
Boxer did not speculate on the cause of the reduction. She just said Congress needed to get to work trying to figure out a way to make up the lost revenue.
"This problem must be addressed by Congress," she said. "A strong transportation system is vital to our nation's competitiveness, and it requires maintaining federal investments in our infrastructure."
Boxer added that "no great country can be a great country without a strong infrastructure.
"No great country can be a great country with their bridges failing or their highways failing," she said. "You've got to move people, and you've got to move goods efficiently and safely."
Boxer said she was issuing "a clarion call to all of our colleagues saying, 'Please pay attention to this, and please be part of the solution.'
"There are many ways to solve this problem, and we can solve it," Boxer said.