A draft of the Boxer/Inhofe amendment just came over the transom from a source in DC close to the negotiations (PDF).  This is a draft from yesterday and negotiations are ongoing, so expect changes. 

Specifically,
enviros are trying to get a "green screen" put in place, so that USDOT
can pick from the priority projects presented by the state DOTs. 
Theoretically this would mean that the Obama administration would make
better decisions about how to spend the money than the states and would
redirect funding to priority transit projects.  Based on the current
language, though, the amendment still gives precedence to the states to
load up their road building projects.

Here are the highlights of the draft circulating as of yesterday:

• The
  amendment Senators Boxer and Inhofe have been working on would increase
  highway, transit and water (clean water and drinking water)
  infrastructure funding in the stimulus by up to $50 billion if other
  funding provided for in the bill is not used quickly.
• This
  amendment would redirect up to $50 billion of funding that would
  otherwise expire at the end of Fiscal Year 2009 in addition (if
  necessary) to unobligated balances from slower-spending programs
  appropriated throughout the stimulus package that have not been
  obligated within a full year after enactment.   
• A
  maximum of $50 billion would be redistributed by the President to
  states for use on highways, transit and water projects, based on a
  priority list of shovel ready projects within 120 days, as determined
  by states.  This list would be provided by each state and certified by
  the Governor, based on priorities that are the product of ongoing state
  and local planning programs.
• Eligibility has been
  expanded far beyond highways alone.  A broad array of projects beyond
  highways and bridges can be funded including transit and environmental
  mitigation for example.  States and localities should give special
  consideration to projects that will bring the conditions of roads,
  bridges, and other transportation system elements up to standard, that
  will result in immediate employment, that will increase the energy
  independence of the United States, and that will provide long-term
  economic benefits.
• This amendment would provide
  additional funding for the clean water and drinking water state
  revolving funds and would maintain the 15% set-aside for green
  infrastructure included in the underlying bill.  This ensures that
  states will be able to implement green projects to reduce energy
  consumption and improve water efficiency with any funding provided
  through the amendment.                     
• This
  amendment takes money that is otherwise not going to quickly stimulate
  the economy and moves it to a program that can get people working
  faster.
• Funds are moved to highway, transit and water
  infrastructure investments under this amendment because they improve
  our nation’s infrastructure and can be under contract in an expedited
  manner.