Sometimes, knowing when to give up is a virtue.

State Sen. Jim Whelan, D-Atlantic, wants to find new sources of funding for the state's bankrupt Transportation Trust Fund. It's a fine goal, but his latest proposal to squeeze some money out of drivers of electric vehicles to maintain our roads and highways isn't the answer.

In February, Whelan proposed replacing the state's gasoline tax with a per-mile fee for all vehicles. Critics derided the idea, saying that it would hurt sales of fuel-efficient vehicles, would tax owners even when they drove out of state, and that it raised the scary specter of big-brother government following drivers' movements.

Now Whelan has retooled the idea, with a proposal to charge a flat fee of about $50 a year to drivers of electric vehicles. It's a marginally better approach, but not one worth pursuing.

It's not that Whelan's wrong. Since they don't pay the gas tax, you could argue that drivers of electric vehicles are getting a free ride. And his pay-by-the-mile proposal didn't come out of thin air. The idea is being discussed nationally and has been tested in Minnesota and Oregon.

Certainly, the state's Transportation Trust Fund is in need of rescue. It is $14.3 billion in debt. All of the money from New Jersey's gas tax of 10.5 cents per gallon, the third-lowest in the nation, goes to pay interest on that borrowed money.

Nor would a $50 fee keep people from buying electric vehicles; they're already more expensive than other cars. But it wouldn't help the trust fund much either. Only about 2 percent of vehicles in New Jersey are powered by electricity. Whatever money the plan would bring in would be like throwing pennies into a several-billion-dollar hole.

Drivers of electric vehicles already contribute to road construction when they pay tolls. In fact, in Atlantic County - Whelan's district - it's pretty difficult to go very far without paying a toll on the Atlantic City Expressway or the Garden State Parkway. It's worse in neighboring Cape May County, where the parkway is practically Main Street. Toll funds from these roadways have been raided in the past to finance other transportation projects.

The proposal is especially strange from a political standpoint. Whelan is running for re-election this year, but it's difficult to see what constituency this bill appeals to. Conservative voters hate the idea of more government intrusion into their lives and new taxes of any kind, and liberal voters love the idea of promoting the use of electric cars.

Whelan has said he wants to start a conversation about finding a stable funding source for our transportation infrastructure, and it's true that his proposals are pretty much the only suggestions that have been made.

But while we can appreciate Whelan's attempt to take on this important issue, he should let this bad idea go.