Interstate 66 near Manassas. (Stephanie K. Kuykendal/For The Washington Post)

FOR FOUR DAYS last fall, along one of the most heavily trafficked corridors in the mid-Atlantic, Virginia state police did something novel: They enforced the law.

They cracked down on Northern Virginia scofflaws driving at rush hour without passengers inside the Beltway on I-66, Northern Virginia’s most critical east-west artery. Since the road opened more than 30 years ago, rush-hour drivers on that segment have been required to carry at least one passenger or be subject to ticket with fines up to $1,000.

The law is widely ignored; at least 20 percent to 30 percent of rush-hour drivers on I-66 are alone in their cars, choosing the (usually slight) risk of a ticket over the hassle of carpooling. After four days of enforcement, the tally was nearly 250 tickets. That sounds like a lot, but it could have been three or four or 10 times as many; police say it’s dangerous to do more on a highway as clogged as I-66.

Those traffic-clogging scofflaws also happen to be voters, which is why politicians in Northern Virginia are afraid of them. So afraid that some state lawmakers would rather protect their “right” to continue breaking the law rather than embrace a balanced, long-term financing plan to alleviate congestion along the corridor.

The problem with Gov. Terry McAuliffe’s plan, in the lawmakers’ view, is that it includes tolls on the inside-the-Beltway segment of I-66. The tolls would apply only at rush hour, and only to solo drivers — the current scofflaws — not to law-abiding carpoolers. But no matter: Some drivers from western Fairfax, Prince William and Loudoun counties feel so entitled to hog lane space, gratis, that they have bullied legislators into taking their side.

A bill sponsored by Del. James M. LeMunyon (R-Fairfax), and similar bills from other area lawmakers, would ban tolls on I-66. Mr. LeMunyon argues that the better solution lies in building more lanes inside and outside the Beltway. That’s true in the long term. The problem is that by eliminating the tolls, the legislation would deprive the state of tens or hundreds of millions of dollars in projected revenue that would pay for the very widening the opponents of tolls say they want. It would also kill funding for an array of other transit improvements designed to divert traffic by enhancing commuters’ options: more buses, parking lots, facilities for carpoolers, etc.

The toll opponents got a dose of reality the other day from state Transportation Secretary Aubrey Layne Jr. He told lawmakers that if the tolls are scrapped, I-66 could still be widened, outside the Beltway, but only by raiding funds earmarked for other, lower-priority road projects in Northern Virginia and elsewhere across the state. That gave downstate lawmakers pause. (Widening I-66 by more than a lane inside the Beltway is another story, with a price tag that would run into the billions of dollars.)

Mr. LeMunyon himself sponsored a bill a few years ago requiring that transportation projects be ranked according to how much they would reduce traffic. Widening I-66 outside the Beltway was the state’s No. 1-rated project. Now Mr. LeMunyon and other Northern Virginia legislators are subverting the funding formula that underpins that project.

If Northern Virginia lawmakers kill the tolls, Mr. McAuliffe may simply acquiesce. If they won’t fund a fix for their own region’s traffic mess, why should the governor go to war?