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After I-95 fiasco, a ‘road weather’ expert digs into snow, ice and jackknifed trucks

Andy Alden has explored the physics, environmental considerations and technologies affecting this specialized realm

Andy Alden, a senior research associate at the Virginia Tech Transportation Institute working on freight, transit and heavy-vehicle safety. (Courtesy of Andy Alden)
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Andy Alden saw the horrendous backups on Interstate 95 that started Monday with both professional detachment and an uncomfortable sense of recognition.

Alden is an expert in truck safety and “road weather,” which looks at conditions on roadway surfaces caused by things like snow and ice. He also was once stranded on an interstate near Memphis under similar conditions two decades ago.

As a senior research associate at the Virginia Tech Transportation Institute working on freight, transit and heavy-vehicle safety, Alden has explored the physics, environmental considerations and technologies affecting this specialized realm.

As the Virginia Department of Transportation continues to review the I-95 incident, including what the agency on Friday called “performance gaps,” Alden spoke to The Washington Post about the broader factors that contribute to such a calamity. The interview was lightly edited for length and clarity.

Q: Virginia State Police said a tractor-trailer jackknifed on I-95 at 8:20 a.m. Monday, marking the beginning of the backup. Within moments, police said more tractor trailers were jackknifing behind it. From the most basic level, why do trucks slip in these circumstances? And why is it so hard to get them off the highway?

A: Trucks are very different beasts than light vehicles. Tractor- trailers, and especially the trailers, are not as advanced as modern light vehicles. And, frequently, you don’t know exactly what the quality of the brakes and the tires are on trailers. They’re kind of a commodity in the freight world. In many cases, they’re not really well taken care of, though with some of the major folks, they really are. The tires on trucks are made more for long-term operation and economy than they are for traction. So you get into that situation, the dynamics of sliding on ice — you hit the brakes, and trucks tend to jackknife. That’s just the physics of things. So what’s a jackknife? Of course, they turn sideways typically, and then sometimes they tip over. And, boy, once you have a heavy vehicle crash on a highway, all bets are kind of off.

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Q: Why is it such a challenge to move a skidded-out truck that’s blocking a highway?

A: Trucks are heavy. They’re over 50,000 pounds in most cases, and the equipment that’s trying to move those trucks around is subject to the same slippage on the pavement that the trucks themselves are. It’s tough. Sometimes you have to use multiple wreckers to move a truck around. It can get complex.

Q: VDOT said it faced two inches of snow an hour for several hours, which overwhelmed its response. Some states like Michigan deal with massive amounts of snow routinely. What’s the challenge in dealing with this?

A: VDOT is relatively well-prepared. They’ve got contractors, or their own people, sitting in snowplows on the side of the road, ready to go. But in many cases, they’re relying upon being able to get those plows mobile and out there where they need to be. And as soon as you have a crash involving a truck, and you’ve blocked off the whole roadway, nobody goes any further, including the plows. Plows don’t have any kind of magical abilities letting them bypass that traffic jam and get out there ahead of it and plow. Had they been able to maintain the traffic flow, if those trucks didn’t crash — and get out there and plow like they normally do — it probably would not have been a major event.

Q: A VDOT engineer said officials were optimistic when the sun came out Monday afternoon, but clearing stuck vehicles took longer than expected, and eventually there were four inches of ice on the road, making the endeavor more treacherous.

A: Typically, VDOT is able to get out there and do pretreatment. That’s where they put brine on the roadway before an event when they know a storm’s coming in. But when they had all that rain that came right before the snow, it would have washed away any kind of pretreatment that was on there anyway. So whether they pretreated or not was really irrelevant. Another thing people need to think about is the salt that we’re putting on our roadways is actually very destructive. It ruins our cars, it ruins our infrastructure — bridges, things like that — and it’s contaminating our environment.

Right now, some of our major water supplies in the Northern Virginia area are so contaminated with salt components that we’re at the EPA limits and it’s jeopardizing people’s health. Those people that have hypertension, the sodium that’s in the water that comes from the salt is actually a health risk for those people. So you just don’t want to go out there and throw down a whole bunch of salt anytime, especially when you know it’s just going to get washed off into the ditches.

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Q: What does your research show us about ways that these kinds of situations might be prevented? Is there hope on that front?

A: Foremost is probably good communication. We’ve been working for years at Virginia Tech Transportation Institute on what’s called “connected vehicle systems,” where a device in your car could provide information about these types of things in real-time, inside the vehicle. So you’re not relying upon your cellphone or any other way of getting that information. You don’t have to worry about the signs above the road. That’s really important. Not only does it tell you you’ve got problems ahead, it lets you know where you can go. And if you encounter slippery roads, you can report that.

We actually foresee a future where the cars themselves act like probes out in the environment, sharing information with approaching drivers and maybe even the road maintenance people, so they can get in there and do something about it.

Q: Is that done today?

A: No, it’s not done. It is an edge case. The technology is there, we’re just moving toward adoption now. I know that VDOT is actually working on some cellphone apps to do those types of things, but the adoption of that in-vehicle technology that comes from the factory is not quite there yet.

Q: As you were watching this meltdown — with Sen. Tim Kaine (D) and other motorists stuck for more than 24 hours — what thoughts were going through your head?

A: Ah, boy. I guess my first thought was empathy, because I’ve been in the same situation before. I’ve been caught on I-40 in Tennessee under very similar circumstances. And you know, I also am the director of the I-81 Corridor Coalition, and this issue of people stranded along roadways has come up before as a concern. You’ve got people that are out there without any resources. You might have a diabetic who needs insulin, and there’s just not a real good way to get that to them.

The barriers we put up along the highways to make them secure, or so that vehicles don’t cross over the median and hit cars head-on in the other direction, those safety barriers also, unfortunately, constrain our response in these kinds of situations. You can’t easily get onto the roads and there are no alternative routes.

Q: VDOT, state police and emergency management officials are doing what they call an “after action review” of the whole incident. What do you want to know about why things went the way they did, and how to make them less severe in the future?

A: As a researcher, I’d like to know a little bit more about the mechanics of what happened on the roadway surface itself. We had this very warm spell, which is unusual, with that warm weather up in the 70s. Then we had rain. Then we had a whole lot of snow. And then we had freezing cold temperatures. That’s a fairly unusual situation, and I’d be really interested to know how — if that’s something we can expect in the future, with global warming or whatever — we deal with that. If we can’t put pretreatment on the road to better enable plowing, is there some other way of dealing with that kind of problem?

I also think about technological solutions, like the communications we talked about. But also, once you have people stranded out there, are there other ways to get things in to them? Could you use drones, perhaps, to drop supplies in to them, especially in critical situations like medical care, food, heat, blankets, whatever is needed? That’s technology that’s fully capable right now that could be used to do that.