Rendering of future I-95/I-695 interchange with toll lanes from MdTA.

Maryland highway planners predicted that if the state didn’t build 7 miles of toll lanes on I-95 north of Baltimore, the road would back up for hours every day. But when the $1.1 billion expansion opens in 2014, it won’t even collect $10 million a year in tolls.

When former Governor Robert Ehrlich’s administration decided in 2003 to add toll lanes to I-95 north of Baltimore, the traffic forecast for 2020 was 238,000 vehicles per day. Now the state predicts 186,000 daily drivers in 2020. Even that assumes growth of 1% per year, although traffic has been flat since at least 2006.

The toll lanes, their promoters said, would benefit even those who can’t afford to pay by taking traffic off the free lanes. Tolls would be set to attract as many cars to the pay lanes as they could carry without backing up. But that policy, it turns out, would only yield $2 or $3 million a year in revenue, barely more than the cost of collecting tolls, so Maryland boosted the rates to match the per-mile charge on the Intercounty Connector.

With a rush-hour toll of $1.75, the 4 toll lanes will carry less than 7% of the total traffic on the 12-lane highway. Truck drivers will avoid them, the Maryland Transportation Authority’s consultants say, “due to the minimal benefit for trucks in saving small amounts of time.” Except during exceptional traffic jams, nearly the only users will be drivers affluent enough not to care much about the toll, leading some to call them “Lexus lanes.”

But folks who can’t afford to use the Lexus lanes will pay a hefty price for them. When construction began, the Ehrlich administration estimated the cost at $830 million. The price tag has now grown by a third, even though transportation officials eliminated some expensive flyover access ramps as a cost-saving measure after Governor Martin O’Malley took office in 2007.

The net toll revenue of around $5 million a year (after subtracting toll collection expenses) won’t begin to pay off the hundreds of millions of dollars in construction debt the state has taken on. The bill will go to drivers on the Bay Bridge, Harbor Tunnel, and other roadways the transportation authority operates, unless it raids the tax-supported Transportation Trust Fund as it did to pay for the Intercounty Connector.

Even toll road enthusiasts admit that the I-95 toll lanes are a “disappointment,” built to meet forecasts that are “now seen as an absurd basis for planning.” This debacle was in fact quite foreseeable. It’s a lesson highway planners should take to heart.