• by Stephanie Pollack and Al Biehler
  • 10

It's a vicious cycle: Our transportation systems emit greenhouse gases that contribute to climate change. And in turn, climate change poses a huge threat to our transportation systems. What can we do?In this photo, two passengers walk alongside a moving MBTA Red Line Train. (atomicity/ flickr)


The transportation of people and goods from one place to another creates about one-third of all greenhouse gas emissions. Of that, 80 percent comes from cars and trucks.

What are the prospects for reducing those emissions? How is global climate change already affecting existing transportation systems? And how will it affect the ways we build and maintain bridges, roads, tunnels and transit systems for the rest of the century?

Noted transportation and environmental practitioners Stephanie Pollack and Al Biehler discuss what’s gone wrong — and what’s starting to go right.

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Stephanie Pollack is professor of practice in law and public policy at Northeastern University and associate director of the Kitty and Michael Dukakis Center for Urban and Regional Policy.

If you care about climate change, you should worry about transportation.

Transportation accounts for 29 percent of all greenhouse gas emissions in the U.S. According to the EPA, the average car owner releases 4.8 metric tons of carbon dioxide each year by driving — far more than the carbon emissions from heating and lighting your home.

But what’s scary about transportation greenhouse gas emissions is not how big they are, but how fast they rise. In Massachusetts, an urbanized state with good energy efficiency programs for our buildings, transportation accounts for 36 percent of our greenhouse gas emissions — and it’s the fastest growing share. In fact, the increase in greenhouse gas emissions from the transportation sector offset the entire savings from all of the commercial and industrial building improvements Massachusetts has made over the last two decades.

The total amount of carbon generated by the transportation system is a function of four factors: vehicles, fuels, operational efficiency of the whole system (e.g., traffic jams), and travel. Transportation officials are reasonably hopeful about the prospects for using technology to reduce greenhouse gas emissions caused by the first three factors. Changing how people travel is the hard part.

If you care about climate change, you should worry about transportation.

If, like most transportation planners, you think the purpose of the transportation system is to move people from one place to another, then you’re going to measure mobility, and you’re going to consider an increase in vehicle miles traveled a positive social good.

But there’s growing school of thought that suggests accessibility, the ability to get the things we need, is what people really want. If the social utility of the transportation system is redefined as such, then mobility becomes a smaller piece of the puzzle.

If the nearest supermarket is 20 miles away, I have to drive (mobility) to buy groceries. But if the nearest supermarket is a few blocks away (proximity), I could walk or ride a bus to buy groceries. Or I could buy groceries online (connectivity) and the delivery truck would emit fewer greenhouse gases than if I and 20 neighbors each drove to and from the supermarket.

It is the ability to change land use patterns by anchoring them with transit that reshapes a region to allow radically different transportation behaviors (i.e. walking, biking, car sharing, mass transit) and therefore a much smaller carbon footprint.

In eastern Massachusetts, less than 3 percent of the land is within a half mile of a transit station — but so are 30 percent of the region’s households. Those households have dramatically lower transportation-related greenhouse gas emissions than do households that lack convenient access to transit.

The bottom line is that we can reduce vehicle miles traveled without sacrificing what the transportation system does for us and our economy, which is to give us access to the things we need. We know how to do it. We’re already seeing results in Massachusetts in the past few years. And a big part of the reason is the walkability of this region and our transit system. We need to build on both of those attributes in order to continue to succeed in reducing the greenhouse gas emissions from our transportation sector.

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Al Biehler is a distinguished service professor of transportation and systems policy at Carnegie Mellon University and former secretary of the Pennsylvania department of transportation.

In the 1990s, Pennsylvania’s population grew 3 percent, but the state’s developed land increased by 54 percent and traffic, as measured by vehicle miles traveled, increased 48 percent. New roads filled with traffic almost as fast as we could build them.

As a result, when former Gov. Ed Rendell appointed me secretary of transportation in 2003, the state Department of Transportation not only had billions of dollars of new road-building projects in the planning stages, we also had a staggering backlog of structurally deficient bridges and roads in poor condition.

We faced the harsh reality that PennDOT simply did not have the money to build everything we were planning and after much internal debate decided to focus on a Fix-It-First strategy.

In the past decade capacity-adding projects have shrunk from 25 percent to 4 percent of PennDOT’s program budget. Meanwhile, the number of structurally deficient bridges has declined steadily over the past five years from over 6,000 to under 4,500. The miles of state roads in poor condition have been cut 37 percent.

Curbing the growth of transportation-related greenhouses gas emissions will require ever more difficult decisions about where and how to invest our transportation dollars.

The biggest challenge we faced was getting our transportation engineers and planners talking with other key stakeholders: local officials, transit agencies, developers, alternative transportation advocates, housing and land use experts. It was also the key to our success.

Here’s one example: PennDOT spent 15 years and $80 million planning for a four lane freeway along a stretch of Route 202, about 30 miles north of Philadelphia. When I met with local officials to tell them PennDOT couldn’t afford the additional $385 million it would cost to build the freeway, well, let’s just say I wasn’t the most popular guy in the room.

Instead, PennDOT engineers and planners worked closely with the affected communities and within three years started construction on an improved Route 202 built at street level and mostly just two lanes wide. At a savings of $185 million, it is sufficient to carry projected traffic, it is better connected with the surrounding towns and roads, and it reduces greenhouse gas emissions. That’s the approach PennDOT initiated across the state.

With the ever-increasing impact of climate change, it’s the approach we’ll need to build on. But adapting current infrastructure to deal with the effects of climate change won’t be easy and it won’t be cheap. To name just a few of the things the U.S. and countries around the world need to do sooner rather than later:

  • Build storm surge barriers and subway flood gates in our coastal cities.
  • Change bridge heights and protect them from the increased scouring from larger, more powerful storms.
  • Rebuild roads that buckle from increased heat.
  • Expand drainage culverts to cope with more violent downpours.

We also need to rethink construction practices to take into consideration the expected weather-related impacts on transportation infrastructure as temperatures rise and as extreme weather events become increasingly common.

Curbing the growth of transportation-related greenhouses gas emissions will require ever more difficult decisions about where and how to invest our transportation dollars. And then the real work of emission reduction begins.


Tags: Climate change, Environment

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  • Harold Ambler

    Most readers of this story, unfortunately, will not know that Earth’s climate system continues to function within historic bounds. In particular, they will not know that Earth has been cooling since the Holocene Optimum, 7,000 years ago. They will not know that the current interglacial, the Holocene, is the coolest of the previous five interglacials. I used not to know these facts myself, and I used to be quite upset about climate change. Now that I’ve done my homework ( I am able to focus on particulate pollution as real environmentalists should.

    • ocschwar

      And apparently, every single scientific organization on the planet has missed the pearls of wisdom you are sharing with us.

  • mememine

    The real problem you remaining climate change believers have is your grandkids explaining you to their grandkids exactly the same way you would explain Reefer Madness to your grandkids. “I see the signs!” “We cannot deny the change!” Right now you doomers look like the last fella ever to show up to the party still dressed in disco duds. Nice job girls. You held a spear of CO2 fear to our children’s backs just to make sure they turned the lights out more often and stayed “environ MENTAL y aware.
    How many climate blame believers did it take to change a light bulb? None but they did have full consensus that it would change, maybe.
    How will history judge Climate Blame Belief?
    -History will note that not one single IPCC warning ever said the end of the world would or will happen, only might and could happen. Check for yourself.
    -History will note that your solution to what we all knew was an exaggeration was to tax the air we breathe with bankster funded and corporate run carbon trading stock markets ruled by politicians.
    -Worst of all, (besides asking why climate blame wasn’t a war crime), is the embarrassment of history remembering us all for begging “OUR” politicians to make the ultimate election promise: To force us to sacrifice our lifestyles to control the climate so the weather is colder and “tamed”.
    Modern day witch burning perhaps?

  • Tobey Pearson

    Can someone tell me two things? How much climate change is man and how much is nature? What transportation systems caused the Earth to warm and end the last ice age 10,000 years ago?

    • ocschwar

      Right now, it’s 100% man. You see, the Milankovich cycles, which caused the earth to warm 10,000 ago, are now driving the earth to cool down. It’s mankind that is overwhelming the cooling phase and instead warming the earth.

  • Sarang Supekar

    Erratum: I believe there is an error in the order of magnitude of annual greenhouse gas emissions from the average car in the US in the article by Prof. Pollack. The figure should be 4.8 metric tons and not 4.8 million metric tons. At roughly 11,500 miles driven per year with a 21 mpg vehicle and with a gasoline a carbon content (upon burning) of 8.8 kg/gallon, the annual vehicle emissions come to 11500 x 8.8 / 21 = 4819 kg = 4.8 metric tons. It’s an easy error to make since metric tons of CO2 is often abbreviated as MTCO2, leading us to interprete the ‘M’ as million.

    Reducing transportation emissions is closely tied to improvement in public transit systems and urban planning, as pointed out by the authors of the article. It is not only socially inequitable to put a carbon tax on gasoline without providing an alternative means of transportation, but also a risky move for an economy that is precariously positioned between recovery and recession. Given the dynamic nature of the vehicle market, and costs per kg of carbon emission avoided, perhaps it makes more sense to first go after the low hanging fruit – the power generation sector.

    • Frannie Carr

      Thank you for catching that. It’s fixed.

  • Michael A. Lewis

    Whether or not the Modern Warming Period is caused by human CO2 production, we cannot engineer our way out of dependence on private automobiles.

    Cars are a status simple, an expression of identity, as necessary to the average American as their cell phone (now increasingly combined). American society and communities are integrally built around cars, and cannot function without them. We will have to rebuild our cities in order to stop using cars.

    Substituting electric cars for gasoline powered cars only shifts the CO2 production to a centralized power plant, or to the manufacturing plant for solar panels. There’s no free ride.

  • Benjamin Wao

    The key to reducing vehicle miles traveled and the social ills that accompany ballooning VMT lies in land use development patterns. As long as private land holders are free to subdivide their land and develop suburban style neighborhoods, far from transit and urban centers, and as long as there are people clamoring to buy into those kinds of developments, no state level policy will be effective to curb VMT. Transportation system congestion and energy use per capita will continue to rise, so long as this is the predominant development pattern. I hate to be fatalist about it but as long as the American dream is a single family house in the suburbs, VMT will continue to rise, plain and simple.

  • Steve Shoap Sr.

    I have invented several ways to make small, energy efficient cars, safer in collisions. Safer small cars would encourage more people to buy them.
    The auto companies won’t talk to me since I am an outsider. I have US patents.