Thursday, July 18, 2013

Extreme Temperatures Are Affecting Every Mode of Transportation

Extreme temperatures are on the rise. We're seeing record-high temperatures across the country, and we're seeing them more often. Two years ago, Dallas-Fort Worth saw over 70 days at 100+ degrees; Wichita Falls, also in Texas, over 100 days. When these heat waves occur, the focus tends to be public health and drought, which is entirely warranted. But the impacts on our transportation system are serious as well, and they affect every conceivable mode of travel.

Cars and Buses:

When high temperatures are sustained for long enough, concrete expands and can buckle, crack, or shatter. This isn't just harmful to the cars, buses, and other vehicles bumping over these holes and cracks; it can be downright dangerous. Besides the potential for irregular roads to cause veering or loss of control, concrete has been known to "explode," lifting chunks of concrete and putting those nearby at serious risk.

Heat-buckled freeway segment in North Carolina, from New York Times.
Asphalt is also at risk of cracking (though usually less severely), but it has its own unique vulnerabilities . It's less stiff than concrete so it deforms more easily in the heat, and can cause roads to end up extremely uneven, unpleasant and sometimes dangerous to drive. In the most extreme heat, asphalt can even come right off the road and stick to tires

Perhaps the biggest problem with heat-related damage is that it's impossible to predict where the cracks, splits, twists, or explosions will occur. This goes for basically every mode of travel. All you can do is patch them as they happen, try not to shut things down for too long, and hope that no one's injured in the mean time. 

Aside from the obvious danger posed by these infrastructure failings, the cost of these constant repairs is high, especially for roads since we have so many. We're already doing a terrible job of keeping our roads in a good state of repair; extreme heat damage is going to absorb more and more of our already-limited routine maintenance budget as the effects of climate change worsen.

Trains and Streetcars:

Photo from PBS.
Just as with asphalt and concrete, steel rails are at risk of overheating and warping. Part of the motivation for this post is today's news that Amtrak is slowing trains in the Northeast Corridor in response to the oppressive heat in the region. Consistently high temperatures can cause "heat kinks," (or, more euphemistically, a "thermal misalignment") which at their worst can lead to train derailments, and forces operators to slow trains where rail kinks and warping are known to have occurred, or be likely. There are tens of thousands of frequent Amtrak users in the Northeast that are currently having their trips delayed by 10-20 minutes due to the extreme heat. It's good that they're putting safety above speed, but they're going to have to make that trade-off more and more often as temperatures continue to increase. In extreme heat, you can't have both.


Airplanes lose lift at higher temperatures, and Phoenix airport has had to cancel flights on multiple occasions due to extreme heat. As more regions of the country begin to approach Phoenix-level highs, we may need to expect more cancellations. Also, this:

At Reagan International Airport, photo by Phillip Dugaw.
Walking and Bicycling:

This is the saddest of the lot, all the more so because it affects youth and the elderly most severely. We're already seeing it across the country: cities are telling their residents to stay indoors during times of extreme heat, discouraging them from getting around on foot or bike. You can't blame the cities, either. Heat exhaustion, heat stroke, and various illnesses made worse by overheating—all are serious concerns and lead to hundreds of deaths and thousands of hospitalizations across the country every year. In California alone, a two-week heat wave in 2006 claimed the lives of 655 people. According to the Chicago Tribune, "[s]earing temperatures kill more people in the U.S. than hurricanes, lightning, tornadoes, floods and earthquakes combined."

From the Chicago Tribune.
This is especially tragic for its timing. Just as we're finally seeing success in turning the tide back toward healthier, more sustainable lifestyles, tens of millions of people are being instructed to stay indoors and rely on air conditioning to get them through half the year or more. Two of the major causes of climate change—personal vehicles and the energy- and carbon-intensive homes that characterize suburban sprawl—have become our only refuge from the environmental disaster we've engineered. We're spending more time in our homes and cars because our homes and cars have made the climate inhospitable to actual humans.

So what can be done? Not much in the short term, unfortunately. Things are going to get worse before they get better, and as they get worse it will become harder to make the changes we know we need to make. Temperatures will increase, and they'll be high more often, so active transportation will be more of a challenge. Damage to our infrastructure from both extreme heat and extreme storms will sap money away from mitigation and prevention efforts. The obvious response is to invest heavily and rapidly in cleaner energy, and to use that energy more efficiently in our homes, businesses, and transportation systems. I'm not yet hopeful though. In a country where we haven't even come to a political consensus on the theory of climate change, much less the role we play in it, we still have a long way to go.


  1. In the long term, infrastructure can be designed to work safely without such compromises even in extreme situations. Russia ordered high-speed trains that are specifically designed to start at temperatures down to -40 (C or F) and to keep running at temperatures down to -50 C. South Korea, which isn't as cold as Russia but is colder than the Northeastern US, has heated switches. The Northeast Corridor's new electrification north of New Haven is designed to withstand hurricane-force winds. Japan and southern France both have earthquake detection systems meant to rapidly stop a train before the main wave of the earthquake gets to it.

    Presumably, there are also systems meant to withstand extreme heat. Saudi Arabia is building HSR, and has far hotter summers than the parts of the US under discussion. Spain and Italy are also quite hot in the summer. India is planning to build HSR, and has extreme heat in the summer before the monsoon season starts; I do not know how reliable its conventional rail network is, but presumably its HSR design specs call for the same levels of reliability of European, Chinese, Korean, and Japanese HSR.

    1. Thanks for the reply Alon. Good points on rail, and I think that highlights one benefit of rail: much less fixed infrastructure is required to move the same amount of people compared to roads. The downside is that a failure can be much more catastrophic, both in terms of lost lives and injury and for mobility.

      I imagine there are heat-resistant road materials as well, but to tear out and replace all of our existing roads with those materials would be astronomically expensive--perhaps we should start using those materials (if they exist) when we do major maintenance on roads and bridges in areas expected to get hotter.

      Again, my biggest worry is that walking and bicycling seem to have the fewest options available for mitigation, and that's really unfair/sad.