With Olympics boosters touting existing and planned transportation infrastructure in Greater Boston as sufficient to handle the international sporting contest, a transportation advocate says the bid documents significantly overstate the amount of upgrades that are in the works.

The document that Boston 2024 submitted to the U.S. Olympic Committee references the state's five-year capital investment plan before listing as "planned investments" $2.2 billion for the South Coast Rail, $300 million "committed" for the expansion of South Station and $400 million for diesel multiple unit (DMU) train service between Newton and the South Boston Waterfront. The bid also includes $120 million for a new commuter rail station in Allston.

According to Rafael Mares, a senior attorney at the Conservation Law Foundation who specializes in transportation and environmental justice issues, those projects overstate by about $2.3 billion the state's funding commitment. "These projects aren't all fully committed yet," Mares told the News Service.

The five-year capital investment plan includes about $255 million for bridges and track upgrades for South Coast Rail, $190 million for DMUs, and $200 million for the expansion of South Station. The capital investment plan (CIP) says MassDOT is seeking public-private partnerships to fund the remaining $700 million to $900 million cost of the South Station expansion. State officials have also said private financing would be a component of the plans to construct a new commuter rail station in Allston. Mares said the CIP does not include any money for that planned station, known now as West Station.

Rich Davey, the former transportation secretary who is now CEO of Boston 2024, said the bid was not intended to be a representation of the five-year CIP. He said the bid looked at the next 10 years and said the administration is free to move projects in or out of the pipeline.

"We're kind of talking in hypotheticals. It's ultimately up to the administration to make transportation decisions," Davey told the News Service. When Davey joined former Gov. Deval Patrick last September to announce plans to build West Station at an old freight yard, he said the project is a "no-brainer."

Mares said MassDOT has not previously said it would build DMU service between the Seaport and Newton. The CIP discusses using DMU trains - which are similar to subway cars - along the Fairmont Line through Boston. He also said the Olympics bid does not identify the funding that would be needed to add the projects to the transportation pipeline.

"Nowhere in the bid documents does it say that there is need to raise additional revenue," Mares said. He said the projects outlined in the bid would take years to be planned and built, meaning decisions about how to pay for them "would have to happen really soon."

Davey said the "greater point" of the bid is that existing upgrades to Logan International Airport, the Central Artery and the Boston Harbor cleanup have put Boston in the position to hold the Summer Games even without additions to the region's transportation infrastructure.

"There's no one transportation project that we need to do to have a successful Olympics," Davey said.

Mares also expressed some concerns about the bid's reference to the potential "relocation of existing facilities" at Widett Circle, the proposed location of Olympic Stadium in a part of the city Boston 2024 dubbed Midtown. The area next to Interstate 93 is surrounded by a Red Line rail yard, which Davey said would remain in place if the stadium is built there.

"Boston 2024 is not proposing to move the Red Line Cabot Yard," said Davey. He said Olympics facilities could potentially be built above the rail yard and he left open the possibility that a nearby bus facility could be moved.

"That's something that we need to have a further conversation with the T about," Davey said. Other current uses of the site include Boston public works storage, the New Boston Food Market wholesale food distribution and cold storage facility in addition to tracks controlled by Amtrak.