Is Our Infrastructure Ready For Rising Temperatures? 416
Hugh Pickens writes "Megan Garber writes that last weekend, a US Airways flight taxiing for takeoff from Washington's Reagan National Airport got stuck on the tarmac for three hours because the tarmac had softened from the heat, and the plane had created — and then sunk into — a groove from which it couldn't, at first, be removed. So what makes an asphalt tarmac, the foundation of our mighty air network, turn to sponge? The answer is that our most common airport surface might not be fully suited to its new, excessively heated environment. One of asphalt's main selling points is precisely the fact that, because of its pitchy components, it's not quite solid: It's 'viscoelastic,' which makes it an ideal surface for the airport environment. As a solid, asphalt is sturdy; as a substance that can be made from — and transitioned back to — liquid, it's relatively easy to work with. And, crucially, it makes for runway repair work that is relatively efficient. But those selling points can also be asphalt's Achilles heel. Viscoelasticity means that the asphalt is always capable of liquefying. The problem, for National Airport's tarmac and the passengers who were stuck on it, was that this weekend's 100+-degree temperatures were a little less room temperature-like than they'd normally be, making the asphalt a little less solid that it would normally be. 'As ironic and as funny as the imgur seen round the world is, it may also be a hint at what's in store for us in a future of weirding weather. An aircraft sinking augurs the new challenges we'll face as temperatures keep rising.'"
Re:News to us in Texas (Score:2, Informative)
I was going to say the same thing about Phoenix. We have at least a couple months of almost continuous 100+ temps and never hear of issues like this.
Re:News to us in Texas (Score:4, Informative)
They've just mixed the asphalt for the expected climate instead of having the same mix that would be used in Dallas, or a different mix again for a hot tropical climate. Other expected problems are rails buckling and problems with elongation of power lines.
Re:News to us in Texas (Score:4, Informative)
Re:Nope. (Score:5, Informative)
Tarmac is formulated for specific climates, so that it heats and flows properly for the maximum temperature expected in that area. For instance, 25 years ago in the region where I live, a Hot day was around 80 degrees. So the asphalt mix used was intended for that sort of climate. Now that our summers mave many days in the mid-upper 90's, and a few that tweak 100, that asphalt is out of it's temperature range.
The reason that they use different mixes depending on climate is that the mixes that set will in a cooler climate, also have some resistance to frost heaving. The mixes that harden at a higher temp are more brittle at freezing temps.
This is probably more than anyone wants to know about asphalt paving or tarmacadam.
Otherwise, yeah, we are sure letting a lot of stuff fall apart.
don't stand in one place (Score:5, Informative)
There is a reason that the area around the terminal is made of concrete and there are concrete pads placed at spots where airplanes sit. It is to allow them to stay in one place without sinking. While heat will hasten the effect, a fully loaded large airplane will sink into any tarmac. I ride motorcycles and on hot days my kick stand can dig through most tarmac quite easilly(I carry a small metal plate to spread the load on hot days).
The idea is to keep moving so one does not sink. Whoever let the heavy aircraft sit on tarmac instead of concrete is to blame for the issue and not the heat. Even on an average day for July I bet the aircraft would have sunk to some degree in three hours.
The solution to this problem is to not stand for more than a few minutes on tarmac. If the delay is longer, return to the gate or wait on a piece of concrete.
Re:Earth won't turn into Venus! (Score:5, Informative)
Damnit, even the worst fearmongers tell us that temperatures will rise by 1 degree per 20 years. Even ignoring the fact that this kind of temperature rise is insignificant in terms of what we're talking about, that's decades or centuries to replace infrastructure.
Instead of worrying about asphalt on streets, I'm worring about brains already having melted in one-too-many climate change activists demonstration.
Get a clue.
"Temperatures will rise by an average of 1 degree" does not imply that temperatures will be ~1 degree higher each and every day. Quite the contrary, climatologists predict that the weather (including temperature) will be MUCH more volatile. That means you will have many days where the temp is >15 degrees above normal, in additional to crazier winter weather etc.
Basically, because the size of weather fluctuations are expected to increase, you will get more days of crazy temperatures that will take a toll on infrastructure.
Sky Harbor (Score:5, Informative)
Sky Harbor (Phoenix airport) doesn't use asphalt runways for precisely this reason: archaeologists would be digging the bones of widebodied aircraft out of the tarpit centuries from now.
FWIW, the record temperature at Sky Harbor was 50C. They had to shut down the airport until it cooled off because the standard tables for flap settings didn't go that high. Now they do.
Re:Nothing new (Score:4, Informative)
Correction to the article, runways are made of thick concrete. Ramps and Taxiways are made of asphalt since they don't need to absorb the impact of an airplane landing gear traveling at 100+ MPH.
Re:Nope. (Score:5, Informative)
Actually, the UK's road system started off as private toll roads maintained by the people who charged tolls on them.
http://en.wikipedia.org/wiki/Turnpike_trust [wikipedia.org]
It was abandoned as being inefficient and the responsibility for the roads turned over to local government. So yes, roads 'should' be run by the state, but not as a natural monopoly, but just because it's actually more efficient to fund the roads through taxes than tolls.
Re:It's never been over 100 in DC before? (Score:3, Informative)
Re:Nope. (Score:2, Informative)
You're mixing your measurements, 2-3 degrees is on a global scale. some regions have experienced more drastic changes. i am sure there are also some regions that have colder winters now, too.
Re:Nothing new (Score:1, Informative)
Concrete lasts much longer, though. Asphalt buckles and develops ripples from the traffic. And you cannot patch asphalt. Asphalt patches get destroyed by traffic because they're never as uniform as the surrounding road. Concrete, on the other hands, patches perfectly.
The only downsides to concrete are that it's expensive (labor intensive), and that you can get really big pot holes in colder climates. If you have money, and you don't regularly get freezing precipitation, than concrete wins hands down every time. Even if you get freezing precipitation, concrete wins, but you have to fix it promptly. That's how Chicago does it.
There are various parts of the country that still have the same interstate that Eisenhower laid down. It was made with good 'ole concrete.
All the old concrete roadways that you love to hate are probably older than you are. When they finally get replaced by aphalt (or rather, are overlaid with asphalt), you'll see how quickly it turns to crap.
Re:Nope. (Score:2, Informative)
That 2-3 degrees would be the global average, but climate change could potentially result in greater local variation [wikipedia.org] in temperature.
Re:Nope. (Score:5, Informative)
In the US, you can always tell the tollways from the freeways -- they're far less well maintained, as the private businesses which own them are interested in extracting as much profit as possible. Since there is no cost incurred from the delays, accidents and/or deaths caused by the poor road quality, the businesses simply don't bother with maintenance. It's the invisible hand of the market at work, not giving a flying fuck about the externalities.
Re:Any mix for -18 to 38? (Score:4, Informative)
So what's the solution for a place like Indiana that can reach both 0 deg F (-18 deg C) and 100 deg F (38 deg C)?
Building the road better, mostly. Layering is important. and drainage is critical. the larger the extremes, the more water you have to get well away from the asphalt.
Re:News to us in Texas (Score:5, Informative)
The performance of aircraft engines at various altitudes and temperatures are well-understood. Before anything the size of an airliner takes off the crew calculates exactly how much thrust is needed to complete the takeoff safely.
Things considered include:
1. Temperature
2. Altitude
3. Takeoff weight
4. Runway length (from start point to end of runway).
5. Any obstructions beyond the end of the runway.
6. Runway slope
7. Head/tailwind
8. Flap configuration
9. Ground conditions (wet, ice, etc - this matters if the takeoff needs to be aborted)
I might have missed something, but there are charts for every aircraft with any model of engines that allow you to look all this stuff up and determine if the takeoff can be performed safely. A safe takeoff is one where the aircraft can reach a safe speed and clear all obstacles should an engine fail right at the point of no return, and also where the aircraft can lose an engine right before the point of no return and stop before the end of the runway. None of this stuff is left to chance.
Usually there is a considerable margin beyond what is necessary for a safe takeoff, and in this case the pilots instruct the aircraft to use less than full thrust. That saves wear and tear on the engines, reduces noise, and also gets rid of the "Top Gun" effect when a jet powered to haul cargo takes off mostly empty.
If the air is too hot to take off safely on any available runway then the plane doesn't take off. Of course, they know that this will happen before they bother to load the plane - they would take on less cargo/etc if they could, or cancel the flight.
Re:Nothing new (Score:5, Informative)
Actually you have it the wrong way around. Most runways are asphalt with concrete landing areas while taxiways are concrete so aircraft can sit on them or long periods of time. Asphalt is used because it does not have expansion joints and is less susceptible to heaving. Here [antigoconstruction.com] is an example of a USAF airfield with just that configuration. Note that the taxi ways are a light colour while most of the runway is dark. In the text it explains exactly what kind of asphalt was used. Here is another example [goo.gl] in Alaska. Notice that the aircraft are sitting on concrete while most of the rest of the taxiways and runways are asphalt.
Re:News to us in Texas (Score:4, Informative)
You got me there. The longest of 3 runways at Sky Harbor/Phoenix is 11,489 feet (others 10,300 & 7,800 ft). At Denver International they have one runway that's 16,000 feet but the other five are all 12,000 feet, not that much longer than at Phoenix. To address another point that's been raised in this discussion, all of those runways at both airports are concrete.
Re:Nothing new (Score:3, Informative)
A highway engineer of my acquaintance told me that in states such as California it's common to use concrete topped w/ asphalt for intersections and a distance out to support the vehicles stopped for traffic lights. If you want to see what happens to heavily traveled intersections where they don't use concrete, come to Anchorage. We have a few that are a nice washboard ;)