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Beyond Skin Deep: The humble roadway is about more than asphalt and concrete. · Thinking Transportation: Engaging Conversations about Transportation Innovations

• 0:14
  Bernie Fette (host): Hello, and welcome.
• 0:16
  Bernie Fette (host): This is Thinking Transportation-- conversations about how we get ourselves and the things we need from one place to another.
• 0:25
  Bernie Fette (host): I'm Bernie Fette with the Texas A&M Transportation Institute.
• 0:30
  Bernie Fette: Simple appearances can be deceiving.
• 0:33
  Bernie Fette: That's certainly true regarding the surfaces that we drive upon every day.
• 0:38
  Bernie Fette: We've invited Darlene Goehl to join us for this conversation, to help us understand more about the humble roadway.
• 0:47
  Bernie Fette: Darlene is a research engineer at TTI, and she leads the Institute's Pavement and Materials Division.
• 0:55
  Bernie Fette: Welcome, Darlene.
• 0:55
  Bernie Fette: Thanks for visiting with us.
• 0:57
  Darlene Goehl (guest): Well, I appreciate the opportunity to talk about highway research.
• 1:02
  Bernie Fette: Can we start with a little history?
• 1:04
  Bernie Fette: I'm wondering if you could tell us when paved roads were first introduced in America and what they were like.
• 1:12
  Darlene Goehl: The first roads were very similar to the Roman roads.
• 1:16
  Darlene Goehl: People are familiar with that in Europe.
• 1:17
  Darlene Goehl: They've heard of the Roman roads; they're still finding them.
• 1:21
  Darlene Goehl: And they were just basically a gravel roadway.
• 1:24
  Darlene Goehl: Large rocks.
• 1:26
  Darlene Goehl: And that was brought over because that was the common practice.
• 1:30
  Darlene Goehl: In the 1800s in England, they started to take those Roman roads and try to improve them the way that they were designed.
• 1:40
  Darlene Goehl: So it started crushing the rock.
• 1:42
  Darlene Goehl: So that was kind of brought over with the British to the United States and we started with a crushed rock and then to kind of keep the dust down, they would mix tar into the top.
• 1:54
  Bernie Fette: Okay.
• 1:54
  Darlene Goehl: And so that became your first paved road, as we would see like a black top, a tar road, tarmac, you've heard that term.
• 2:02
  Darlene Goehl: So that's kinda where that came from because the person that created crushing the rock, his name was McAdam.
• 2:09
  Darlene Goehl: So they mixed the tar into the crushed rock.
• 2:11
  Darlene Goehl: They called it tarmac.
• 2:13
  Bernie Fette: Got it.
• 2:14
  Darlene Goehl: And of course, a lot of people used, uh, bricks in the larger cities.
• 2:18
  Darlene Goehl: Again, the goal is to get outta the mud.
• 2:21
  Darlene Goehl: And so you want a hard surface, that's all weather.
• 2:25
  Darlene Goehl: So late 1800s, you know, bricks mixing the tar in the top were the most popular types of roads in the U.S.
• 2:34
  Darlene Goehl: Then as the oil industry boomed, we started using asphalt and asphalt and tar are not the same thing.
• 2:42
  Darlene Goehl: Tar comes from a process from coal and asphalt comes from oil.
• 2:47
  Darlene Goehl: That's the main difference between the two.
• 2:50
  Darlene Goehl: And so we now use asphalt and really we don't use tar.
• 2:55
  Darlene Goehl: It was the early 1900s, really, when we started to get to more of a, what you would think of the type of paving you see now where you have black top roads and some concrete roadways.
• 3:06
  Bernie Fette: So if we, if we fast forward just a little bit, I was telling my friend, Cathy Reiley yesterday that I'd be having this conversation with you.
• 3:14
  Bernie Fette: And she told me,"oh, you have to ask her to talk about the non-splashing pavement!" And I'm glad that she suggested that because I think it's a fine example of how research led to innovation in a way that's tangibly beneficial, tangibly noticeable to people who use roadways every day.
• 3:36
  Bernie Fette: I wonder if you could explain briefly what my friend was talking about with the non-splashing pavement, and maybe also talk a little bit about what you see as the more noteworthy milestones in the evolution of roadways.
• 3:48
  Darlene Goehl: Ultimately, the goal of pavement is for it to be safe for you to drive on.
• 3:53
  Darlene Goehl: Well, as we improve safety of the roadway, we look at the materials that we use to construct the pavement.
• 3:58
  Darlene Goehl: And one of the more recent safety improvements is to remove splash and spray.
• 4:06
  Darlene Goehl: So it helps you have better visibility when you drive.
• 4:09
  Darlene Goehl: It helps, uh, avoid the hydroplaning problems that you may see in wet weather.
• 4:14
  Darlene Goehl: The surfacing was developed.
• 4:16
  Darlene Goehl: It's actually a porous friction course is what Texas calls it.
• 4:19
  Darlene Goehl: Basically, it's large rocks stuck together with a lot of asphalt and it has voids in it so the water will flow through.
• 4:28
  Darlene Goehl: Think of a popcorn ball, all stuck together, and it has air all in it.
• 4:33
  Darlene Goehl: So that's kind of what it looks like.
• 4:34
  Darlene Goehl: That's about the size of the rock.
• 4:36
  Darlene Goehl: It's about the size of pieces of popcorn and they're stuck together.
• 4:39
  Bernie Fette: That is great to use an analogy like that.
• 4:42
  Darlene Goehl: Yeah.
• 4:43
  Darlene Goehl: I have to explain lots of things to my family also, and they don't like the technical part.
• 4:49
  Bernie Fette: Okay.
• 4:50
  Bernie Fette: If we step away from the one that you just described, that helps to channel the water from the roadway and thereby really improve visibility, if we step away from that one, what would say some of the other really noteworthy milestones are in pavement evolution and how research contributed to those?
• 5:10
  Darlene Goehl: Yeah, it, it really started in the early 1900s when we started using these, uh, newer, well, I say newer materials for the 1900s.
• 5:17
  Darlene Goehl: It was newer, right?
• 5:18
  Darlene Goehl: Because oil was a new thing.
• 5:20
  Darlene Goehl: Cars were new.
• 5:21
  Darlene Goehl: Originally we had roads for wagons pulled by horses.
• 5:25
  Darlene Goehl: And as we started becoming automated using automobiles, trucks that are running on pneumatic tires, we have a different way and different amount of load that goes through the pavement structure.
• 5:39
  Darlene Goehl: So to be able to support the traffic, we have to design the pavement with that in mind, and the way those forces and the loading comes from the weight of those vehicles.
• 5:52
  Darlene Goehl: And so it made us look at different materials and now we have more people riding and you can imagine how rough it was to ride in a buckboard.
• 6:00
  Darlene Goehl: And then you go to a car with a pneumatic tire air-filled.
• 6:04
  Darlene Goehl: And so you expect a much smoother ride.
• 6:06
  Darlene Goehl: So from that, we need to go to something that we can pave that is smoother.
• 6:12
  Darlene Goehl: We wanna control dust and other things.
• 6:14
  Darlene Goehl: So we started mixing in asphalt.
• 6:17
  Darlene Goehl: The Texas Highway Department started in 1917 and really took over a lot of the more local roads and was able to do a lot more influence with how we do research.
• 6:27
  Darlene Goehl: Then in 1950, the Texas A&M Transportation Institute was created to support the Texas Highway Department in transportation research.
• 6:37
  Darlene Goehl: The Interstate System was started in 1956.
• 6:41
  Darlene Goehl: And from that there was a national road research program.
• 6:45
  Darlene Goehl: They had a road test that was done from 1958 to 1960, where they built a segment of the road.
• 6:52
  Darlene Goehl: They had the military come in and just drive on it continuously with loaded trucks, to look at how the loading and those trucks affected the pavement.
• 7:03
  Darlene Goehl: And that's really the basis for the pavement design procedures we have now.
• 7:09
  Darlene Goehl: And before everybody just used kind of a cookbook recipe, put eight to 10 inches of crushed rock in and surface it.
• 7:17
  Darlene Goehl: And now we have much more technical methods for designing pavements based on the type of vehicles that are gonna travel on that.
• 7:26
  Darlene Goehl: And that all led from that road test that was created that in the 1958 to 1960 timeframe
• 7:33
  Bernie Fette: For lots of us, it might seem simple.
• 7:37
  Bernie Fette: Mix up the asphalt and the rocks, spread it out where you want the road to be, and then pack it down nice and flat, and you're done.
• 7:44
  Bernie Fette: At least it looks simple on the surface.
• 7:46
  Bernie Fette: But what exactly goes into building a high-quality roadway?
• 7:50
  Bernie Fette: Why is it more precise and complicated than it might look?
• 7:56
  Darlene Goehl: Okay.
• 7:56
  Darlene Goehl: So one of the challenges we have to build a road that other people don't think about is we're not building a road in a factory.
• 8:04
  Darlene Goehl: We're building our road outside.
• 8:07
  Darlene Goehl: It rains.
• 8:09
  Darlene Goehl: It freezes.
• 8:10
  Darlene Goehl: We have traffic that we have to deal with while it's under construction.
• 8:14
  Darlene Goehl: You know, we need to keep the public moving.
• 8:16
  Darlene Goehl: So there's a lot of things that interfere with us trying to build a quality product.
• 8:22
  Darlene Goehl: And unfortunately, the weather is probably one of the biggest challenges that we have to construct a good pavement structure because ultimately we wanna do is keep the water out.
• 8:33
  Darlene Goehl: 'Cause the water softens all the material,'cause we're using, you know, soils, natural soils, we're using rocks that are crushed.
• 8:41
  Darlene Goehl: All these things soften when they get wet.
• 8:43
  Darlene Goehl: So ultimately what we wanna do to build a good road is keep water out.
• 8:47
  Darlene Goehl: And if we're building it in the rain, then it takes longer and we have to dry it.
• 8:50
  Darlene Goehl: And that the other thing too is challenging, I know it's hard for the public to understand why does it take so long to build a road.
• 8:57
  Darlene Goehl: Again, if I was building the road in a plant, I could work on it every day.
• 9:02
  Darlene Goehl: If you actually look at how many days are available to construct, when you take out rain days, holidays, freezing days, you're only left with about half a year you can actually physically work on the roadway.
• 9:15
  Darlene Goehl: So sometimes it's a challenge just because it looks like we take forever, but we take forever because the weather interferes with us.
• 9:23
  Darlene Goehl: And one of the things that's challenging in Texas is Texas is a huge state and different areas of the state have different materials.
• 9:32
  Darlene Goehl: The eastern part of the state doesn't have a lot of rock.
• 9:35
  Darlene Goehl: It's more river gravels and silts from the meandering rivers.
• 9:40
  Darlene Goehl: So it, it doesn't have good material as you go west, it's more arid.
• 9:44
  Darlene Goehl: You have more rocks, you get into mountainous areas and the material quality is much better.
• 9:50
  Darlene Goehl: There's less rain.
• 9:52
  Darlene Goehl: So it's actually easier to construct as you go west.
• 9:56
  Darlene Goehl: And one of the things we like to do with research is you have to recognize that you have different things affecting what you do and you have to design to overcome those.
• 10:06
  Darlene Goehl: And you also have to try to design to use your local materials so that you can be very cost-effective.
• 10:14
  Bernie Fette: So what you're describing might also help to explain why building a road is not only more complicated than most of us think, it's also helps to explain why it's so expensive-- why building a roadway can cost several million dollars a mile.
• 10:29
  Darlene Goehl: Yes.
• 10:30
  Darlene Goehl: And like everything that we purchase, it's all tied to delivery of materials, hauling fuel prices and everything to build a road has to be hauled in.
• 10:41
  Darlene Goehl: And so, for example, if you're in east Texas and you don't have aggregate, you have to either bring that material in by rail and then haul it to the site.
• 10:52
  Darlene Goehl: Or you have to truck it in from somewhere.
• 10:54
  Darlene Goehl: Maybe say I-35 central Texas area going west is where most of the aggregate is at.
• 11:01
  Darlene Goehl: And so you've gotta bring those materials in.
• 11:03
  Darlene Goehl: So that's a huge cost and the amount of material that you need to build the roadway.
• 11:09
  Darlene Goehl: It's a lot of material.
• 11:10
  Bernie Fette: Right.
• 11:11
  Bernie Fette: 'cause you're talking hundreds of tons of materials.
• 11:13
  Darlene Goehl: Oh yes, yes.
• 11:15
  Bernie Fette: We've talked a little bit about the history and I was hoping we could shift toward the future.
• 11:21
  Bernie Fette: Can you help us understand to what extent might the emergence of self-driving cars change how we build streets and highways.
• 11:33
  Darlene Goehl: Now, if you look at the lane that you drive in, it's about 12 foot wide and you can see where people drive,'cause it tends to look a little bit blacker.
• 11:42
  Darlene Goehl: You can kinda see the path.
• 11:44
  Darlene Goehl: Well, if you look at that path where people normally drive, it tends to be on each tire about three foot wide.
• 11:49
  Darlene Goehl: So there's some wander when you drive just naturally within the lane, that kind of distributes the weight of that car over half the lane.
• 11:58
  Darlene Goehl: So about six foot total.
• 12:00
  Darlene Goehl: When you go to a self-driving car, they're gonna drive in a path similar to a train on a track.
• 12:07
  Darlene Goehl: And what happens now instead of that tire meandering over a three-foot area, it's probably gonna be stuck in about a one-foot area.
• 12:16
  Darlene Goehl: So you have a more concentrated load on the pavement within that area.
• 12:20
  Darlene Goehl: And that's gonna change a little bit in how we design that pavement to hold that loading up.
• 12:25
  Darlene Goehl: It's gonna have to be stiffer and we're still researching that, how those effects can cause those problems with those platoon vehicles.
• 12:34
  Darlene Goehl: That's what we're anticipating.
• 12:36
  Bernie Fette: And so that narrower distribution of weight that you're talking about ends up causing more wear and tear in a more concentrated pathway?
• 12:46
  Darlene Goehl: Yes, sir.
• 12:46
  Darlene Goehl: That's what happens.
• 12:47
  Bernie Fette: Okay.
• 12:48
  Bernie Fette: And so what that means is then you may have to change the way that you build roads in the future, in part, by what you mix to make those roads, to help determine the strength or the resilience that you need?
• 13:01
  Darlene Goehl: Yes.
• 13:01
  Darlene Goehl: And so we design now to try to have the roadway structure support the loading for 20 to 30 years.
• 13:08
  Bernie Fette: Okay.
• 13:08
  Darlene Goehl: And we resurface around probably every 12 years just due to the weathering effects.
• 13:16
  Darlene Goehl: The sun oxidizes and causes cracking in the top.
• 13:19
  Darlene Goehl: Sometimes we'll have to add a layer of asphalt in order to just help keep the waterproofing.
• 13:25
  Darlene Goehl: Because again, the environment causes some cracking in the road.
• 13:29
  Darlene Goehl: Ultimately, we need to keep water out.
• 13:31
  Darlene Goehl: So we have to continue to waterproof, but those layers have a certain strength and that strength allows them to support a load that comes through the tire.
• 13:42
  Darlene Goehl: And as that load is more concentrated into one spot, it looks more stress in that spot.
• 13:48
  Darlene Goehl: So I'll have to do some additional research on how you design that to continue to last the amount of time that we expect it to before we go in there and do work.
• 14:00
  Bernie Fette: And will you also have to consider that pavements in the future, roadways in the future, to accommodate autonomous vehicles, that those, those pavements may have to have sensors embedded?
• 14:11
  Darlene Goehl: Right now, the technology is working off the striping and the reflectivity in the striping.
• 14:17
  Darlene Goehl: Uh, and you can see if you have a car that has some of the pilot assist and those type of things.
• 14:22
  Darlene Goehl: When the line marking drops off, say you have a ramp entering or you have a turn lane starting.
• 14:29
  Darlene Goehl: Sometimes the cars will pull you towards that open spot, trying to keep you in the center of the lane.
• 14:35
  Darlene Goehl: And those markings have to be refreshed on a three-year cycle.
• 14:39
  Darlene Goehl: So that becomes very expensive if you're using those markings to control.
• 14:43
  Darlene Goehl: And there has been talk about putting other sensors within the pavement to help guide the cars.
• 14:49
  Bernie Fette: Pavement research for self-driving cars is one area.
• 14:53
  Bernie Fette: But what about other major research needs that you can foresee?
• 14:58
  Bernie Fette: If you had a really big check from a research sponsor tomorrow, what's the most pressing need that you would start with?
• 15:05
  Darlene Goehl: One is the material challenges we have now.
• 15:08
  Darlene Goehl: We see this in every industry with the supply chain problems.
• 15:12
  Darlene Goehl: And we use polymers in our pavement structures to help stiffen and work better through environmental changes through the climate change of just in a normal year.
• 15:23
  Darlene Goehl: Last year, there was a polymer supply issue.
• 15:26
  Darlene Goehl: And so there were some changes to those polymers.
• 15:29
  Darlene Goehl: We think that's causing some problems on the roadways leading to some early failures that we didn't expect to see, but we need to do some research to figure out what happened, what changed, why the material still meets all the requirements yet it's not performing.
• 15:44
  Darlene Goehl: So that's one thing is, supply chain issues still occur.
• 15:49
  Darlene Goehl: We will try to, and in the manufacturers that, that we still have to continue to build the road.
• 15:54
  Darlene Goehl: So they're trying new things.
• 15:57
  Darlene Goehl: The second thing that I think is important is to take the lessons that we learned from research and apply those and provide whatever training that's needed to others who, who maybe not see our original research and are involved in the sponsorship of that research to help promote its use and to get it out there so that it can benefit all the taxpayers.
• 16:19
  Darlene Goehl: The state of Texas is unique in that TxDOT has on its system a lot of roadways that other states would consider to be not on the state system.
• 16:30
  Darlene Goehl: All the farm-to-market, ranch-to-market type roads that are on the Texas system are not on other state systems.
• 16:36
  Darlene Goehl: They're controlled by counties and others.
• 16:39
  Darlene Goehl: So because of that through the years through research and other things developed design methods for those rural roads that are not necessarily the same as the national design because national designs require bigger pavements again, because they're made for like U.S.
• 16:57
  Darlene Goehl: highways, state highways, interstate, much more traffic, much more loading.
• 17:01
  Darlene Goehl: And I think there's a huge opportunity if we had the money to take outreach and teach these things we've learned through research to help more rural communities apply this technology and to be able to do more cost-effective designs and get all surface roads.
• 17:20
  Darlene Goehl: I know, you know, like for example, in Texas, we still have many, many counties that the county commissioner runs the road crew, right?
• 17:29
  Darlene Goehl: And they're, they're not engineers and that's okay.
• 17:31
  Darlene Goehl: That's what we needed.
• 17:32
  Darlene Goehl: But there's so much information out there that, you know, they're not trained to do that.
• 17:37
  Darlene Goehl: That would help them and the taxpayers of the state that for me, I, I just see that there's an opportunity there to go out with some outreach.
• 17:47
  Bernie Fette: It probably wouldn't be a stretch to say that we sometimes take reliable roads and highways for granted.
• 17:53
  Bernie Fette: If you had just half a minute to explain to the average person why having good roads is so important, what would you tell that person, maybe this would be your elevator speech?
• 18:05
  Darlene Goehl: The reason that good roads are important is because especially in the state of Texas, everyone travels by the roadway.
• 18:13
  Darlene Goehl: Texas is a huge state.
• 18:14
  Darlene Goehl: We travel several hours just to visit relatives.
• 18:18
  Darlene Goehl: We have things that we buy goods and services that we use every day that are brought to us from other parts of the country, from other countries through ports and to have the roadways in good shape so that we can get the delivery of the things that we buy, that we use every day, that we feel safe to drive and visit our family or friends or take a vacation.
• 18:41
  Darlene Goehl: Those things are important.
• 18:43
  Darlene Goehl: And while we seem to be constructing I know the roads continuously, you know, it's very important to keep those roads in good order, in good shape.
• 18:53
  Darlene Goehl: We don't wanna have potholes in them that could cause damage to our cars.
• 18:57
  Darlene Goehl: We want a good safe road that we feel comfortable traveling on.
• 19:01
  Darlene Goehl: And in order to do that, you know, we have to, uh, maintain those roads and we have to build those roads to a sufficient strength that it supports all the traffic that's gonna travel on that roadway.
• 19:15
  Bernie Fette: This is something that I like to ask each one of our guests.
• 19:19
  Bernie Fette: What is it that motivates you to show up to work every day?
• 19:23
  Darlene Goehl: I think some, you know, something that you use every day, like the roadway, it's very interesting to me to come in and work and feel like you've contributed to overall society and that improvement.
• 19:38
  Darlene Goehl: And I had somebody tell me one day that we had developed a standard for a construction technique that improved safety and the person made a comment to me that you don't realize how many lives you saved by coming up with that detail.
• 19:58
  Darlene Goehl: And that made me feel really good is, you know, something that we use and we talk about safety, but safety is really important and we all drive the roads.
• 20:06
  Darlene Goehl: Our family drives the roads and we want our families, our friends, ourselves, we want everyone to be safe when they drive on that.
• 20:13
  Darlene Goehl: And so when you can do things to contribute, to improving the safety for everyone, that's really worth doing.
• 20:22
  Bernie Fette: Darlene Goehl.
• 20:23
  Bernie Fette: Research engineer and pavement expert at TTI.
• 20:26
  Bernie Fette: Darlene, thank you for sharing your time and your knowledge with us.
• 20:30
  Darlene Goehl: Thanks for asking me to come on the podcast.
• 20:33
  Darlene Goehl: I appreciate that.
• 20:37
  Bernie Fette: It's sometimes easy to take our streets and highways for granted.
• 20:41
  Bernie Fette: They've become so reliable that we tend to forget how much we depend upon them for our every need.
• 20:48
  Bernie Fette: For trips as routine as a drive to work or as urgent as a response to a medical emergency.
• 20:55
  Bernie Fette: And as simple as they seem, that appearance conceals a structure that's more complex-- one requiring precision in physical science that's built upon decades of advanced research.
• 21:10
  Bernie Fette: Thank you for listening.
• 21:12
  Bernie Fette: We hope you'll be back for our next episode, and a conversation with Shawn Turner, a self-described evangelist who's leading TTI's emerging studies in the world of big data.
• 21:24
  Bernie Fette: Where it's coming from and how it's quietly but dramatically reshaping the way that we transport ourselves and everything we need.
• 21:33
  Bernie Fette: Thinking Transportation is a production of the Texas A&M Transportation Institute, a member of the Texas A&M University System.
• 21:42
  Bernie Fette: The show is edited and produced by Chris Pourteau.
• 21:45
  Bernie Fette: I'm your writer and host, Bernie Fette.
• 21:47
  Bernie Fette: Thanks again for listening.
• 21:50
  Bernie Fette: We'll see you next time.