Even with increased ridership, some major metropolitan transit agencies are struggling more than usual these days as the credit crisis messes with their funding and ailing banks suddenly call in huge loans, asking for millions of dollars on short notice. Transit agencies in Atlanta, Chicago, Los Angeles, San Francisco, and Washington, D.C., have been affected by the turmoil, caused in large part by the collapse of insurance giant AIG. One bank recently told D.C.’s Metro that it owes some $43 million by the end of next week; the agency could soon owe as much as $400 million to creditors. “The worst-case scenario is that we could end up having to come up with $100 million to $300 million overnight,” said Marc Littman of Los Angeles’ Metropolitan Transportation Authority. Many of the struggling transit agencies that had major assets tied up in complicated deals with AIG have asked the U.S. Treasury Department for help. With federal help, said D.C. Metro’s Carol Kissal, agencies would be able to fix their financing woes and satisfy creditors “so [then] the banks would not be looking to take their greed out unnecessarily on public transit.”