Benefits of Asphalt Paving on Road Noise and Ride Quality

Did you know that the use of asphalt pavement compared to other paved surfaces could reduce road noise by 7-10 decibels? In the latest episode of Road Maps for Texas Local Agencies, our hosts discuss how asphalt paving reduces road noise and improves ride quality, tips on ensuring proper hearing protection and more.

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Transcript

SPEAKER_01 0:01

Welcome to Roadmaps, the podcast for Texas local agencies and the firms that support them to plan, design, build, and maintain local roads. On roadmaps, we break down design, mix types, construction, and maintenance, sharing plain-spoken, practical insights you can put to work right away. Asph is a flexible pavement engineered for optimum performance so your community gets stronger, safer, longer lasting roads. The roadmap's philosophy is simple. Stay flexible. Enjoy today's episode. Hello, welcome to today's episode. We're going to be talking about the benefits of asphalt pavements for noise and ride quality. Before we get started though, Sam, you want to do a safety share with us?

SPEAKER_00 0:45

Absolutely, thanks, Larry. Again, we start every episode with a safety share, and today we thought it'd be prudent to talk about hearing uh protection and noise safety because we're talking about uh noise and ride quality of asphalt pavements.

SPEAKER_01 0:58

Makes sense.

SPEAKER_00 0:59

So a couple of the notes we've got. Uh hearing protection should be used if you have to raise your voice more than just standard level talking to a person standing beside you. So anytime you're having a conversation, if you have to raise your voice, you should be uh using here some kind of hearing protection. When we think about the work we do on the roads, almost everything we do, all the equipment we use generates noise. And it's real important to protect our hearing because once it's gone, there's no recovering from it. One thing to keep in mind though, uh we want to be careful when we talk about uh hearing suppression, and when we talk about uh, you know, some of the earmuffs and things like that, we want to still be able to hear alerts and warning messages, we want to still be able to hear traffic, we still want to be able to hear horns. So we don't want to eliminate all background noises, but we do want to when we're jackhammering, when we're standing beside a piece of equipment, when we're on a compactor, uh something like that. We want to make sure we're protecting our hearing, but we're not uh reducing the noise level to a to a point where we can't hear the ambient noises around us. There are some really good electronic devices that uh, you know, you think about the shooter earmuffs that uh really do a good job when there's a uh a loud noise, it it restricts that, but it still lets ambient noise through. And so there's some real good op options out there for really noisy environments. Um earplugs, they're widely available. I think almost every company, if not every company, uh has them for your employees. If they're not available, um as an employee, you need to ask. As a uh supervisor, we need to be providing at the very minimum earplugs for all of our employees every shift. Um I didn't realize is the noise reduction rating on earmuffs and hearing protection uh earplugs, it's not reduced on a one-to-one basis. So if we've got a 27 decibel rated earplug, that earplug is uh the the formula is minus seven divided by two. So 27 minus 7 is 20 divided by 2 is 10. So that is going to reduce the decibels by 10. It does not reduce the decibels by 27. So again, that's something that uh we need to remind people of is let's not think we're getting more protection than we actually are. But enough about that. Let's dive right in and talk about the noise and ride benefits of asphalt pavements. Alright, so Larry, as we're talking about the uh noise and smoothness benefits of asphalt pavements. Some of the things that kind of jump off the page to me is is really when we talk about noise pollution and and in some of these urban environments, the road noise is uh is a real thing. Um I've seen studies before showing uh like a seven to ten decibel reduction in uh road noise from an asphalt pavement versus some other paved surfaces. One of the things that I thought was interesting was a I don't know if you knew, a three decibel reduction to the listener sounds like you've doubled the distance away from the road. So if you're 10 feet off the road, think of the house, right? If you've got a 20-foot setback from the road, uh a three-decibel reduction would make it seem like you're 40 to 50 feet set back off the road. Um and then a 10 decibel reduction, listeners perceive that the sound is cut in half. So those are major benefits that we see with asphalt pavements, aren't they?

SPEAKER_01 4:59

Yeah, no, they they really are. Um and you know, the it may not sound like a lot, but three, four decibels is, as you pointed out, it's a big difference. Um, you know, you when we're talking, having a conversation like you and I are right now, we're running about somewhere around 60 decibels. You know, maybe a hair less if we're speaking soft, maybe a hair more if we're talking a little bit hair louder, but you know, and then if you really raise your voice, you're only raising it six, seven decibels. Um, but it sounds a heck of a lot louder.

SPEAKER_00 5:33

So absolutely, yeah.

SPEAKER_01 5:35

So small changes in that decibel level has a big impact on on how you're how you're hearing it.

SPEAKER_00 5:45

How you're perceiving that sound. Right. Yeah. So tell it, didn't you you went for a drive the other day, didn't you? Tell me about that.

SPEAKER_01 5:52

I did, I did. You know, our buddy Jim Warren, who uh everyone in the asphalt world knows Jim. Uh he's our technical director. Uh he he gave me his decibel meter because I was talking about some roads uh I drive around Austin quite a bit, and so I was uh I had this thing on and uh very carefully. I wasn't looking at it when I should have been looking at the road. That's good. But anyway, uh I I drove around and kind of transitioned through different types of asphalt surfaces around the city, coming from our office down south in Butta up to where I live on the north side of town, and I crossed over from asphalt to concrete three times, you know. So uh uh I had that thing on and was um and and you could see it was it was significant, you know. When you're driving and you can kind of hear on a smooth asphalt roadway, and I transitioned on some of these concrete pavements, and they were, you know, frankly, quite a bit louder. And I was talking about it, and so Jim shows up in my office and says, Here's a decimal meter if you really want to go play with it. So this isn't scientific uh because uh you know I didn't have it, but but the point is that uh it was very noticeable, and you know, I was driving around those asphalt roadways, and they were, you know, when you're getting up above 50 miles an hour, 50, 60, 5 miles an hour. 50. I thought you told me you drive home at 90. Yeah. I wish I could, you know, if there wasn't so much traffic. But it was noticeable that when you were at those speeds, the asphalt pavement was running somewhere uh 60 to up to 64, 65 decibels, depending on the surface and and that kind of stuff. Um, you know, and of course part of that is the engine noise. So I mean, from a relatively speaking, though, when I would transition onto the concrete pavements, they were consistently 66 to 68, 69. Okay. And so that is a uh it was a very uh repeatable uh what I call uh a research project uh in the cab of my truck, so I don't think it would pass any kind of FHWA or uh research uh uh peer review, but it was definitely repeatable that there was uh three, four, five uh decibel difference uh change between the flexible pavement, which is asphalt we call it flexible, in uh in the concrete, the rigid pavement. So it it was noticeable and I uh kind of made a bunch of notes on that. So that's neat. And it was the sound is a lot, you know, back to what you were saying. The that change in three, four decibels, how significant you really do pick up on that. Absolutely. How it how you hear it when you're driving down the road.

SPEAKER_00 8:28

You know, you know, you you talked about different surfaces, and that's one thing, you know, in our our previous talk we talked about uh different mix types and different aggregate structures, and um I think studies have shown that an open graded structure does a lot better job at absorbing noise. Now it's not applicable in in all scenarios, but uh you can get a a two or three decibel reduction by going from a dense graded mix to an open-graded mix, uh assuming that that mix type is still applicable for for your given situation.

SPEAKER_01 9:00

Yeah, you can, you can. And uh I think one area where we've seen this, you know, so the the these porous friction courses we've talked about in previous episodes, you know, uh uh down around the Houston area, the the Harris County Toll Road Authority overlaid some of the Sam Houston tollway with uh, you know, which was a concrete pavement, but they they overlaid it with PFC uh one to help with uh with splash in water, you know, from a safety standpoint it's really beneficial uh and it's higher speed roadways, but uh um it also gave a real significant noise reduction to it. And you know, back to the idea of uh trying to keep things quieter. I mean you see in the urban environments around the state, um we got sound walls going up everywhere, if you've noticed, right? Absolutely. You see these things, they're not cheap.

SPEAKER_00 9:49

Yeah.

SPEAKER_01 9:49

Um and sometimes uh you can get the same benefit to property owners, residentials' homes, people's homes. Sure. You can get the same uh benefit uh uh of a sound wall by changing the pavement type. But uh again, Laz, you stressed it's it really is if it's the right application.

SPEAKER_00 10:10

Yeah. Now another benefit, you know, we talked about say uh um smoothness. Umother pavements have shown to be uh safer, smoother pavements have shown to require less maintenance, um, less maintenance on the road, less maintenance on the cars. Um what how does uh how does smoothness affect uh I don't know like your suspension in your car and everything else when you're going over over bumps and and hitting those concrete joints every 20 feet uh down the road?

SPEAKER_01 10:46

I mean the smoother pavement is definitely less wear and tear. I mean, specifically on your uh wheel alignment and on your suspension components. You know, it it's uh uh you know I'm not gonna go you know overboard and say that you know uh an asphalt road's you know your suspension is gonna last twice as long as on a concrete road, but I will say that it is you know a fact that it you know less wear and tear on your suspension system on a smoother, on a smoother roadway.

SPEAKER_00 11:13

You know, it's it's interesting when we talk about smoothness and ride quality. I was going through Text Ot specs the other day, and I know we're um we're focusing on on cities and counties and local agencies, not necessarily Text Ot, but uh Text Dot ride quality spec on their asphalt specs, um I'm gonna call even money where where you know text dot pays bonuses and they assess penalties for smoothness and for for densities for various other factors, but for smoothness, uh even money on asphalt is is uh an IRI of 65. Even money on concrete is an IRI of 85. That IRI is that International Roughness Index. So that tells me that uh the expectation is that we can get um 20 points better with an asphalt pavement, which 20 points on 85, that's worth 25% smoother on an asphalt road, right out of the bat uh is the expectation.

SPEAKER_01 12:20

Yeah, and you and you definitely you feel it. You definitely feel that. I mean it's like when you're driving, it's like it's what is it that you feel, how how you feel, and smoothness is something, it's kind of like I can tell you about smoothness, but anybody driving, they know smooth when they hit it. You know, it's it's it's a more kind of almost visceral, you know, uh reaction to a smooth roadway.

SPEAKER_00 12:41

So it kind of goes back into noise, is is it it sounds quieter, it rides smoother, it's a it's just a more pleasurable experience for everybody.

SPEAKER_01 12:50

Yeah, and uh, you know, I think there's so much data over the last many decades now that uh it's really indisputable. It's indisputable. And I think that um, you know, from a safety standpoint, a smoother road has some real benefits, and I, you know, and that's a big deal. Um you're on a smoother road, you're gonna have more consistent uniform tire contact. So that feeds into a couple things. One is the friction, the the the contact with the roadway. Um things like that. Um, you know, so I mean that's uh you know uh the smoother the road, the safer it is, too.

SPEAKER_00 13:32

So we've got safety benefits, we've got uh costs, we've got maintenance of the road, we've got maintenance of the the vehicles, uh, we've got noise benefits. We've if we're shaving three or four decibels off, that's uh doubling the it's in effect doubling the distance people are away from the road, which can maybe help with uh sound barriers and other uh sound abatement uh um strategies, I guess, that uh to to cut back.

SPEAKER_01 14:04

Yeah, I think there's no there's no doubt about it. Uh the smooth, you know, it's gonna we're talking about smoothness and noise, um, and they in a lot of ways go hand in glove. I mean we can talk all you and I could talk three hours on each topic, noise or smoothness, but they are kind of uh a symbiotic uh relationship between those two things, and uh and it's important. If you can get a quieter road and make it smoother, it's significantly more well functionally it's better and from safety and like you saying cost, but from a from a driver perspective. From a driving perspective, it's very significant. Absolutely.

SPEAKER_00 14:45

So, Larry, one more thing that I saw as I was doing my uh little bit of research that I I did for this, I I came across, I don't even know what this acronym is because I'd never seen it before, but a NCHRP. You've probably heard of it, the National Cooperative Highway Research Program.

SPEAKER_01 15:02

I've been involved in a few of those studies back in my uh back in my research years, we had some contracts. Well, there you go. NCHRP contracts on uh pavement data collection, a little bit different area.

SPEAKER_00 15:13

But they did a study and and uh it was a few years ago, but they concluded that a uh 50% reduction in IRI resulted in a 15% longer pavement life. So when we talk about uh uh reduced maintenance, we talk about uh more pleasurable driving experience. We're also getting longer life pavements out of smoother pavements.

SPEAKER_01 15:38

Yeah, that's that's true. And we were talking about the you know cost benefits of smoother pavements in terms of maintenance of the roadway and all that, but uh yeah, it's that's a great point because we didn't really, you know, think about the the long the pavements last smoother pavements last long. That's another thing that has been proven through uh extensive research over the over the years.

SPEAKER_00 15:59

And uh you know, and from a from a constructibility standpoint, um as an asphalt pavement is a continuous pavement, right? It it even though there are joints, they're um longitudinal. There are longitudinal joints, there are some transverse joints, but they're you know they're they're uh density controlled and and if built properly they you know they last a long time. But we really eliminate those uh uh transverse and longitudinal joints that cause uh um the bumps and dips and and kind of that repetitive noise uh that you get in in some other pavement types.

SPEAKER_01 16:39

Yeah, that's true. And you know, uh jointed concrete pavements uh were a heck of a lot more common, and we see them more in urban areas, you know. So if you think about it, you know, your house slab is a concrete slab. Well, when you're setting forms and setting on on a jointed concrete pavement, those joints are there to kind of control and keep that slab behaving as best as it can, and then you go on to the next one. So you're really putting together a bunch of uh slabs together in um in, you know, and in fairness, Texas, you know, when you're talking about the highway system, they use a thing called continuously reinforced concrete. Um, but uh you know, and those are smoother than their own counterparts, which are jointed, but a CRC is not as smooth as a uh asphalt roadway, and so yeah, that that uh that smoothness does have a uh a benefit on the long-term performance. Smoother pavements last longer.

SPEAKER_00 17:34

Well, I hope everybody enjoyed our conversation on the benefits of asphalt pavements and and their effect on noise and ride quality. Uh Larry, why don't you highlight today's project of the month?

SPEAKER_01 17:44

Okay, yeah, we love doing this project of the month uh for each episode. And uh this month, the project of the month is going to be Comel County, Texas. Uh, for those of you who may not know where that is, it's kind of around New Bromfels area. And uh the Comel County uh engineering group uh implemented over the last couple of years an overlay program, um, and it has been really successful. Uh they uh had been doing a tremendous amount of chip seal uh projects every year, and uh they found that it was actually more cost-effective to implement and bring in-house an overlay program. Uh we work closely with them at Tech Sappa, and uh they have uh really benefited from it, and so that is our project of the month.

SPEAKER_00 18:35

Way to go, Comal County.

SPEAKER_01 18:36

Yeah, way to go, Comal County. So, Sam, you know what time it is? What time is it, Larry? It's top ten time, and it is today with the top ten reasons you want a smooth, quiet road.

SPEAKER_00 18:48

Well, Larry, number 10 is you're sick and tired of residents complaining about a low, loud, bumpy road.

SPEAKER_01 18:55

Number nine, it's hard to have a hands-free conversation when the road is louder than the caller you're talking to.

SPEAKER_00 19:03

Larry, the number eight reason you want a smooth, quiet road, when your wife is scolding you from the passenger seat, you want to make sure you hear her clearly. You better.

unknown 19:12

You better.

SPEAKER_01 19:13

Uh number seven, you just put on a clean shirt, and the last thing you want to do is have coffee distilled all over it.

SPEAKER_00 19:20

The number six reason you want a smooth, quiet road, you can't tell the difference between the rhythm beats of the song you're listening to and the joints every 15 feet in the concrete pavement you're driving over.

SPEAKER_01 19:32

Number five, your baby just fell asleep in the car seat, and you really want it to stay that way.

SPEAKER_00 19:39

Larry, the number four reason you want a smooth and quiet road, you'd like your car suspension and alignment to last the life of the car.

SPEAKER_01 19:47

Yeah, that'd be nice. Number three reason, less bumps and vibration will reduce fatigue. And that is an important one because that's a safety consideration.

SPEAKER_00 19:56

Absolutely. Number two reason uh to want a smooth and quiet road, smooth pavements, improved tire grip, and braking, making things safer.

SPEAKER_01 20:07

And number one, because darn it, everyone deserves a smooth, quiet pavement, and you'll get it with asphalt. Thanks for joining us for today's conversation on the noise and smoothness benefits of asphalt pavements, and we look forward to seeing you on the next one.

SPEAKER_00 20:23

And remember, stay flexible.

SPEAKER_01 20:29

Thanks for tuning in for this month's episode of roadmaps. If you enjoyed today's episode, feel free to like and subscribe, and follow us on our social media channels at Texas Asphalt Pavement Association. Stay flexible, and we'll see you next time.