WASHINGTON — The Senate is poised to pass an overhaul of highway and transit programs that gives states greater flexibility over how they spend federal aid and streamlines environmental regulations to get projects built faster.

More than 20 amendments — including proposals to allow states to charge tolls on interstate highways, provide tax credits for alternative energy and cars that run on natural gas, and permit more flights over the Grand Canyon and other national parks — are set to be decided today in an all-day marathon of voting.

The measure would spend $109 billion over less than two years.

However, that’s still far short of the spending level that two congressional commissions have said is needed if the U.S. is to maintain its aging roads and bridges and bus and train systems.