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Are We Missing an Environmental Opportunity in the Plan to Replace the Canal Bridges?

Eve Zuckoff
Cars drive across the Sagamore Bridge on an October afternoon. The bridge is among the nine most congested roadways in the state, according to 2019 report by the Massachusetts Department of Transportation.

The Army Corps of Engineers wants to replace the aging Bourne and Sagamore bridges. The proposed plan has received widespread support, but it leaves out any consideration to offset increased traffic with a commitment to public transportation. 


Every day, thousands of cars and trucks labor up the slope of the Bourne Bridge, often taking up more than one of the narrow lanes. 

The Bourne and Sagamore bridges are the only ways to get on and off the Cape by land for the 215,000 year-round residents and 4 million annual visitors. But these 84-year-old bridges won’t be here for much longer. 


“With congestion the way it is, we believe that that replacement makes a lot more sense than continued maintenance,” said Scott Acone, project manager with the U.S. Army Corps of Engineers. The agency owns and maintains the bridges. 


Under the Army Corps' recommendations, the new bridges would be at least 120 feet wide, compared to the existing bridges' 48-foot width. The new bridges would include an extra lane for local traffic going each way and feature a median, shoulders, and a separate bike-and-pedestrian lane.

Now, some watchdogs are questioning the Corps’ recommendations, asking where these bridges fit into building a sustainable Cape Cod. 

“This is the opportunity to say hold on, wait a minute, what's going on here?” said Stephen Buckley. Buckley lives in Chatham. Before retiring, he spent more than 25 years working as a federal environmental engineer. “It’s called the law of unintended consequences," he said. "Might we be inadvertently making it better in one place, but worse in another place?”

He points to a recent report by the Massachusetts Department of Transportation that indicates if the Bourne Bridge is replaced the way the Corps is proposing, the volume of cars crossing onto the Cape during peak times could increase by 25 percent, from 2,825 cars per hour to 3,545.

“That's a significant number,” Buckley said.

In other words,  the Cape will remain the same small bucket, but the hose pumping people into it will be much bigger. 

According to Acone, it’s an unnecessary worry.

“We're going to create a more efficient flow," Acone explained. "And so as a result, more vehicles per hour can cross the bridge as opposed to waiting in traffic. So you'll see the peak number go up. That doesn't necessarily mean more vehicles overall are going.”

It doesn’t necessarily mean more vehicles overall are going, says Susan Handy, a professor of environmental science and policy at University of California, Davis—but that increased capacity can lead to something else.  

“The phenomenon we're talking about is what's called 'induced travel',” Handy said. She explained that traveling during peak times could be made easier by the new bridges, but that benefit could be only in the short term.


“What simple supply-and-demand relationships from economics tell us is that if you reduce the cost of something, people are likely to consume more of it,” Handy said.


To a tourist, reducing the cost means minimizing the pain of travel. Like, not sitting in hours of traffic to get on or off the Cape. 

“That's sort of the ‘if you build it, they will come’ phenomenon,” Handy said. “In other words, more driving.”

More driving doesn’t just create more congestion. It also has a huge environmental impact. 

The transportation sector makes up 42 percent of greenhouse gas emissions in Massachusetts. These emissions are the single greatest drivers of climate change. To fight that, in recent years the state has announced goals to reduce the number of cars on the road.  


“I don't think we can solve climate change without solving transportation,” said Chris Neill, a senior scientist Woods Hole Research Center.


Neill says the designs for the new bridges don’t advance the state’s environmental goals. In fact, they bring us in the wrong direction.  

“This is a perfect little microcosm of where opportunity exists to rethink things,” he said. 

Not in the plan to redesign these bridges is a commitment to increased public transportation with dedicated bus lanes, or expanded rail service, which experts say would help reduce the number of cars on the road and, in turn, carbon emissions.  

Neill says this is a once-in-a-lifetime opportunity to build a more sustainable future for the Cape. 

“If we can't design an infrastructure project on Cape Cod to at least stop growth in carbon emissions,” he warned, “we're not really doing what we need to do.”

The public comment period on the proposed new bridges project ends November 15th. Comments can be submitted online.

Eve Zuckoff covers the environment and human impacts of climate change for CAI.