Traffic congestion in Bethesda on Oct. 18. (Sarah L. Voisin/The Washington Post)

Watching the Montgomery County Council prepare to vote on plans for massive development in downtown Bethesda, I have been reminded of one of the main lessons I learned when I was chairman of the Nuclear Regulatory Commission: Official studies have a remarkable ability to define reality for planners and regulators. Even when these studies defy common sense, their numbers and projections create a kind of artificial reality that is difficult to dislodge.

Montgomery County is in the process of approving a new sector plan that would allow existing square footage to increase to 32.4 million square feet in downtown Bethesda — that’s 8.8 million more than it now has. Some of this space would be for offices, and the rest would be residential (nearly 8,000 new residential units). If approved, downtown Bethesda would look like Rosslyn or Tysons Corner.

Developers want to go forward because they expect to generate considerable income from young professionals eager to move somewhere close to the District on the Red Line, with many bars and restaurants. And Montgomery County planners are eager because they anticipate a tax revenue windfall. They also argue, with some justification, that if there is to be development in Montgomery County, it’s better that it be in areas dense with public transport than out in, say, Germantown where cars are the main mode of transport.

But there is one major problem with these plans: They would bring more people (with more cars and more children) to a location where the public schools are already bursting at the seams and where drivers experience daily a kind of traffic Armageddon during rush hour on the Wisconsin Avenue corridor, affecting local residents and D.C. commuters alike.

And, according to Montgomery County regulations, there is supposed to be traffic mitigation when volume at key intersections exceeds certain levels, and a development moratorium when a school cluster is forecast to be 120 percent of its anticipated capacity.

Enter the official studies on which the planners rely. Anyone who lives in the East Bethesda or Battery Park neighborhoods will tell you that since Walter Reed Army Medical Center was merged with the National Naval Medical Center in Bethesda, travel times to take a child to soccer practice or to pick up an infant from day care have doubled. And the drive often is punctuated by the frustration of watching the traffic on Wisconsin barely move when the lights turn green because of all the cars that have already poured in from Walter Reed National Military Medical Center and the National Institutes of Health. The proposal to move Marriott to downtown Bethesda with 1,200 parking spaces will only make this situation worse.

But when local residents make this point in meetings with planners, they are told not to believe their lying eyes. Remarkably, official studies showed that traffic improved when Walter Reed moved to Bethesda. It seems that these studies used wires across the road to measure the number of cars that moved across them in a set period of time. And gridlock reduced the number of cars that could get from Point A to Point B in a set time.

Planners also relied on studies in which a person is hired to sit at a key intersection on a particular day and count cars. Such studies are notoriously unreliable and measure volume, not vehicle delay, a measure of actual congestion. The mathematical relationship between volume and delay is not linear, so one is not a good proxy for the other. If you pick the wrong intersection, or if you count cars on a sunny day, traffic will appear lighter than usual. It would be more accurate to put cameras at key intersections for days or weeks and have computer programs analyze the footage to generate vehicle counts or to have computer programs record the transit time for index cars between intersections. But, instead of redoing their traffic studies more rigorously, Montgomery County planners have proposed a new rule, currently before the council, under which buildings in newly designated “red” zones no longer would require traffic-impact studies for approval or mitigation.

Then there is the issue of schools. Planners cite Montgomery County Public Schools as a major draw for Bethesda’s new urban residents, but they have no plans to address crowding at Bethesda schools. My daughter attends Bethesda Elementary, which just completed a major expansion. But, with 598 students now in a school with a recently expanded capacity of 577, it is already officially over capacity. The planners did not predict this, partly because their models assume that replacing two-bedroom teardown homes with six-bedroom homes does not generate more schoolchildren.

Montgomery County’s official projections for school enrollments around downtown Bethesda consistently underpredicted enrollments for years, often by 20 percent. A member of the planning advisory board said the problem was caused by residents in single-family homes having more children than they were supposed to. Rather than holding planners accountable for poor projections, he blamed local residents for failing to conform to official plans.

The long-term solution is for Bethesda to incorporate as a city with its own mayor and council who would be accountable to local residents. Montgomery County is so large that its leadership has lost touch with local neighborhoods, and its council members live outside Bethesda, which they see as the “economic engine” for the rest of the county, not as a place with a quality of life to preserve and constituents to be listened to.

If development continues apace without fixing the infrastructure, the livability of downtown Bethesda neighborhoods will be destroyed. We need a moratorium on development so Bethesda’s traffic congestion and school crowding can be addressed based on realistic studies, before new buildings go up. Bethesda needs smart growth, not reckless overbuilding based on wishful thinking masquerading as objective planning.