All five candidates attended the live debate on BBC Somerset earlier at the Numatic factory in Chard.
Labour's manifesto includes plans to delay a proposed upgrade to the A358 from the A303 to the M5 near Taunton.
In December the coalition government committed to dualling the route as part of a scheme to upgrade the South West corridor.
Labour candidate Sheena King said her party wanted to introduce a rail fares freeze up until 2017 and to promote greener transport.
"We do want to upgrade the road (A358) but priorities lie with rail travel and greener forms of travel at the moment," she said.
Conservative candidate Marcus Fysh said: "I don't think we can do without an upgrade of the A358 and A303.
"The A358 particularly is the route between this area (south Somerset) and Hinkley Point (the site of the new nuclear power plant). We need that road to be upgraded."
David Laws from the Liberal Democrats said: "We've got to dual the A303 and A358.
"It's absurd that these days in the summer, traffic is taking an hour queuing up at Stonehenge to get to the West Country. That's really bad for the economy of our area."
Green candidate Emily McIvor said the proposed road scheme was "flawed" and would be "a short-term fix".
"All the research shows that if you improve roads and increase capacity that will just result in increased traffic."
Simon Smedley of UKIP said he supported transport improvements "if they're done within budget and carefully".
He said the Â£50bn set aside for the HS2 rail project (linking London and the north of England) "should be spent across the country on transport projects".
The candidates for the constituency are:
Marcus Fysh - Conservative
Sheena King - Labour
David Laws - Liberal Democrat
Emily McIvor - Green
Simon Smedley - UKIP
Transport issues in Somerset have been debated by candidates hoping to become the next MP for Yeovil.