Photo by dougtone on Flickr.

Travelers on Maryland’s newly-opened Intercounty Connector (ICC) highway see a road that seems empty and overbuilt.  Yet the Maryland Transportation Authority, which runs the road, says that traffic is slightly heavier than forecast.  Can both be right?

Yes, they can. 

The ICC could carry 70,000 cars a day without backing up even in the busiest part of rush hour.  Last month it carried 21,000 per day, and the state expects traffic volumes to stay below 50,000 each day even after drivers have a few years to learn about the road.  The ICC was built to be too big for today’s traffic.  It was designed for 20 years of future sprawl.

According to the state’s forecast for building the ICC, things will look very different in 20 years, and the road will no longer be overbuilt.  18 years from now, traffic forecasters project that the busiest segment of the ICC (between New Hampshire Avenue and I-95) will fill up in the busiest hour of the evening rush hour. 

But the state’s forecast also assumes that gas will cost $2.50 a gallon, adjusted for future inflation.  If instead, gas costs $10 a gallon in 2030, traffic on the ICC is projected to be about 40% below the $2.50/gallon forecast.

With higher gas prices, the overall drop in driving would be smaller, but rising gas prices would take cars off all roads.  With parallel routes less congested, fewer drivers would be willing to pay the high ICC tolls.  The project consultants make an educated guess that a $2.50 increase in the price of gas would cause people to drive 10% less.  Their model calculates that a 10% drop in miles driven on all roads would cause a 16% drop in traffic in the ICC.

Moreover, the forecast assumes more sprawl development. To their credit, forecast authors Wilbur Smith Associates adjusted the official population projections from the Metropolitan Washington Council of Governments, putting a little more future growth in DC and less in outer suburbs.  But the forecast still projects outer suburbs to add more people and jobs overall than inner areas. 

The forecast also assumes that wealthy and poor neighborhoods will be in the same places in 2030 as they were in 2000. Yet today, the affluent are migrating inward, while the population farther out — which is the ICC’s potential market — is becoming less affluent and thus less likely to be willing to pay high tolls.

Over the next 2-3 years, traffic on the ICC will almost surely increase as drivers get more familiar with the road.  But even then it will be half-empty.  And what happens after that depends on events that no one can predict with certainty. 

If the price of gasoline stays where it is now, the migration of the affluent into DC and Arlington halts, and McMansions spring up like weeds again in exurban counties, the road will indeed be filled with traffic in the evening rush hour 20 years from now.  But if the demographic trends of the last five or six years continue, and gas keeps getting more expensive, the outcome will be very different.  The ICC will stand forlorn, half-empty at its busiest moments; a $3 billion relic of a policy mistake. 

There’s nothing at all wrong with building for the future.  The planners of Metro thought big, and we are all better off as a result.  The question about the ICC is whether it was built for the future, or for a past age of cheap gasoline and sprawl that is gone forever.