Work to widen I-66 for tolled express lanes along I-66 outside the Beltway July 1 in Gainesville, Va. (Jahi Chikwendiu/The Washington Post)

THE ECONOMIC fortunes of Northern Virginia and suburban Maryland are linked, but nothing ensures that they march in lockstep. An array of variables will translate into unequal distributions of prosperity, prospects and population going forward — not least the divergent approaches the two have taken to their most critical highways.

Northern Virginia is on its way toward completion of a nearly 100-mile network of tolled express lanes on the Beltway, Interstates 66, 95 and 395 that are already used daily by tens of thousands of commuters and others. Most of it was financed, built and managed by the private sector, which keeps most of the revenue and spares taxpayers most of the burden of a $1 billion investment.

By contrast, a proposal by Maryland’s Republican governor, Larry Hogan, to add express toll lanes to the Beltway through Montgomery and Prince George’s counties, and to Interstate 270 heading north to Frederick, faces uncertain prospects and opposition from local officials, all Democrats.

In suburban Virginia, construction crews are busy expanding the express-lane network, which will not end congestion for most drivers but will keep it from getting unimaginably worse. In suburban Maryland, politicians are taking potshots at a plan that would position the region — and some of the nation’s most congested roads — for the future.

Make no mistake about what that future has in store. The Washington region is on track to grow by more than 1 million people by 2045, and car usage nationally is expanding faster than the rate of population growth. Transit is key to accommodating the region’s population boom, as well as to slowing climate change, and elected officials, including Mr. Hogan, have taken important steps toward improving transit options. But transit alone will not avert a future of pervasive gridlock.

In Maryland, critics of Mr. Hogan’s proposal are right that more road-building will increase demand. But given projected growth, it is folly to imagine that the existing road network is adequate. The real question is what degree of misery officials today will inflict on commuters tomorrow.

The express lanes’ opponents warn that the project will lose money, putting taxpayers at risk. The evidence suggests the opposite: Transurban, the company that has built and operates most of the toll lanes in Northern Virginia, says its profits are healthy and long-term projections are robust. The fact that the company is rapidly expanding the network, extending the 95 Express Lanes to Fredericksburg, reflects its confidence in a simple fact: There is plenty of driver demand.

Critics deride the network as “Lexus lanes” for the rich; to be sure, toll prices, which fluctuate according to demand to keep traffic moving swiftly, can get expensive. But the existing lanes remain free — they’d be even more congested without the express lanes — and no one is forced to use the express network, on which carpoolers and express buses also travel without charge. Maryland would be wise to adopt the same model.

Mr. Hogan’s plan comes with costs, including several dozen houses that would likely be razed to build the express lanes and hundreds more whose backyards would be affected. Nonetheless, it is a sensible response to a predictable crisis that threatens to consign his state to perpetual also-ran status in the regional economic sweepstakes.