(Bill O’Leary/ The Washington Post)

More grim news about federal funding for the nation’s transit, highway and bridge projects: The Department of Transportation forecast Tuesday that the money for those repairs and expansion will begin to run short by the end of July.

The Highway Trust Fund is running low on cash primarily because it depends for revenue from the 18.4 cent per gallon federal gas tax. Inflation and more-fuel-efficient vehicles have eroded fuel-tax income. Transportation Secretary Anthony Foxx is on a bus tour through the Midwest and South this week, in part to drum up public pressure for Congress to find a new means to fund transit and highway projects.

Sen. Patty Murray (D-Wash.), chairman of the subcommittee on transportation, called the USDOT forecast, “a wake up call to Congress.”

“The Highway Trust Fund is heading toward an avoidable crisis as early as July, and if we don’t act, could lead to a construction shutdown on our nation’s roads and bridges. Every day that Congress waits to address this looming crisis, states will be forced to make difficult planning decisions, as many already have, to delay projects that improve roads and bridges in their communities,” Murray said in a statement. “We cannot stand by, as the Highway Trust Fund nears critically low levels, and lose new investments in our roads and bridges, especially when these are the very projects that ensure businesses can move their goods quickly and efficiently and help ease congestion for commuters across the country.”