As he plans his two-year budget proposal, the state’s rapidly-depleting fund for transportation infrastructure is a major headache, Gov. Ned Lamont told a business audience on Friday. The state’s Special Transportation Fund is slowly but steadily going broke and could be exhausted by 2024. And updated transit infrastructure remains a key to the state’s future economic success and viability, Lamont told an online economic summit of the Connecticut Business and Industry Association. Lamont presented a mixed picture of transportation financing, with locally generated revenues falling but more cash expected from the Feds in the Biden administration. In the pandemic, however, with many fewer cars on the road, many state Department of Transportation projects were able to pivot to daytime construction, saving the state money, Lamont said.