National Academies Press: OpenBook

Inertial Profiler Certification for Evaluation of International Roughness Index (2018)

Chapter: Chapter 4 - Use of IRI for Construction Acceptance

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Page 49
Suggested Citation:"Chapter 4 - Use of IRI for Construction Acceptance." National Academies of Sciences, Engineering, and Medicine. 2018. Inertial Profiler Certification for Evaluation of International Roughness Index. Washington, DC: The National Academies Press. doi: 10.17226/25207.
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Page 49
Page 50
Suggested Citation:"Chapter 4 - Use of IRI for Construction Acceptance." National Academies of Sciences, Engineering, and Medicine. 2018. Inertial Profiler Certification for Evaluation of International Roughness Index. Washington, DC: The National Academies Press. doi: 10.17226/25207.
×
Page 50
Page 51
Suggested Citation:"Chapter 4 - Use of IRI for Construction Acceptance." National Academies of Sciences, Engineering, and Medicine. 2018. Inertial Profiler Certification for Evaluation of International Roughness Index. Washington, DC: The National Academies Press. doi: 10.17226/25207.
×
Page 51
Page 52
Suggested Citation:"Chapter 4 - Use of IRI for Construction Acceptance." National Academies of Sciences, Engineering, and Medicine. 2018. Inertial Profiler Certification for Evaluation of International Roughness Index. Washington, DC: The National Academies Press. doi: 10.17226/25207.
×
Page 52

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49 This chapter indicates the states that use IRI as the smoothness index for construction accep- tance and the policy the states use to specify the IRI for construction acceptance, based on the information that was obtained from the 44 states that responded to the survey. Smoothness Specification A smoothness specification indicates the level of smoothness that is required on the final paved surface of a pavement. The smoothness specification will also provide a method to deter- mine areas of localized roughness and how to correct such areas. The smoothness specification specifies the range of smoothness that the contractor needs to achieve on the final paved surface of a pavement to obtain full payment. Many state DOTs use the IRI as the smoothness index to judge the smoothness of the final paved surface of a pavement for both AC and PCC pavements. However, some state DOTs use the profile index (PI) that is determined from profilograph measurements as the smoothness index for PCC pavements or for both AC and PCC pavements. In the past, the PI was commonly used as the smoothness index to judge the smoothness of the final paved surface for both AC and PCC pavements. However, many state DOTs that used the PI have transitioned to using the IRI, and several states that are currently using PI are planning to adopt the IRI as the smoothness index to judge the smoothness of the final paved surface. Use of IRI for Construction Acceptance In the survey, the state DOTs were asked if they used an IRI-based smoothness specification for the final paved surface of AC pavements, PCC pavements, and bridge decks. Forty-four state DOTs responded to the survey. Two state DOTs (i.e., Georgia and Tennessee) indicated that they use an HRI-based smoothness specification. However, as IRI is strongly correlated to HRI, an HRI-based smoothness specification was considered to be similar to an IRI-based smooth- ness specification. In this synthesis, the responses provided by the two state DOTs that use HRI were considered to be the same as if they were using the IRI when reporting the results from the survey. The results from the survey regarding the use of IRI-based smoothness specifications are shown in Table 7. Six state DOTs indicated that they do not use either the IRI or the HRI as the smoothness index in their smoothness specifications for AC and PCC pavements. The percentage of state DOTs that responded to the survey and that are using an IRI-based smoothness specification for AC-surfaced pavements, PCC-surfaced pavements, and bridge decks were 86%, 59%, and 20%, respectively. Twenty-six out of the 44 state DOTs that responded to the survey (i.e., 59% of the responding state DOTs) use an IRI-based smoothness specification for both AC and PCC pavements. C H A P T E R 4 Use of IRI for Construction Acceptance

50 Inertial Profiler Certification for Evaluation of International Roughness Index Out of the six states that do not use IRI or HRI-based smoothness specifications, four states use a PI-based smoothness specification for AC, as well as PCC pavements; one state uses a PI-based smoothness specification for PCC pavements and a Ride Number–based smoothness specification for AC pavements; and one state—where there are no PCC pavements in the high- way network—uses a smoothness specification based on the Ride Number for AC pavements. Figure 12 shows the number of state DOTs that responded to the survey and that use an IRI- based smoothness specification categorized according to the following: • Used only on AC pavements, • Used only on AC pavements and PCC pavements, • Used only on AC pavements and bridge decks, and • Used on AC pavements, PCC pavements, and bridge decks. One state DOT that responded to the survey and declared that it is using an IRI-based smoothness specification for AC pavements, PCC pavements, and bridge decks indicated that it is in the process of transitioning to IRI. Florida DOT—which does not use an IRI-based smoothness specification—indicated that it has implemented a developmental IRI specifica- tion for AC pavements, and it hopes to implement an IRI-based smoothness specification for AC pavements once sufficient projects are completed in each district. This state DOT plans to Surface Responding State DOTs Number Percentage (%) AC-surfaced pavements 38 86 PCC-surfaced pavements 26 59 Bridge decks 9 20 Table 7. Use of IRI-based smoothness specifications. Figure 12. Distribution of the use of IRI-based smoothness specifications for pavements and bridge decks by the state DOTs responding to the survey.

Use of IRI for Construction Acceptance 51 extend the IRI-based smoothness specification to PCC pavements after it is implemented for AC pavements. Illinois DOT, which does not use an IRI-based smoothness specification, indicated that it has stipulated IRI-based specifications on pilot projects to introduce such specifications to contractors. Of the state DOTs that have implemented an IRI-based smoothness specification for AC pave- ments, all (except for one) with more than 5% of PCC pavements in the state highway network have also implemented an IRI-based smoothness specification for PCC pavements. Several state DOTs with less than 5% of PCC pavements in their highway network have implemented an IRI-based smoothness specification for their PCC pavements. One reason some state DOTs that have an IRI-based smoothness specification for AC pavements but do not have such a specifica- tion for PCC pavements may be because some states do not construct PCC pavements, or only a few miles of PCC pavements are constructed in those states. Policy on Specifying IRI for Smoothness The survey asked the state DOTs for their policy on requiring the IRI-based smoothness speci- fication on construction projects. The choices provided for this question were the following: • The DOT has a policy that specifies the roadways for which the smoothness specification must be applied. • The districts in the DOT have the option of using or not using the smoothness specification on a project at their discretion. • If a policy other than the above two policies is used, specify the policy. Figure 13 summarizes the response from the 38 state DOTs that indicated that they use an IRI-based smoothness specification. Twenty-nine state DOTs indicated that they have a policy that specifies the roadways for which the smoothness specification is applied, while five state DOTs indicated that the dis- tricts in the state DOT have the option of using or not using the smoothness specification Figure 13. Distribution of the policy on the use of IRI-based smoothness specification by the state DOTs that responded to the survey.

52 Inertial Profiler Certification for Evaluation of International Roughness Index on a project. The four state DOTs that indicated that they use a different policy provided the following responses: • The assignment of the smoothness specification to a project is decided during the design phase. • The state DOT, not the districts, has the option of using or not using the smoothness speci- fication on a project. • The state DOT uses a special provision for smoothness and selects the projects to apply the smoothness specification. • The state DOT is currently working on a policy to use the IRI-based smoothness specification.

Next: Chapter 5 - Collection of Inertial Profile for IRI Construction Acceptance »
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TRB's National Cooperative Highway Research Program (NCHRP) Synthesis 526: Inertial Profiler Certification for Evaluation of International Roughness Index determines the state of practice of certification of inertial profilers at the national and international levels. Inertial profilers are used to collect the repeatable and reproducible road profiles analyzed to calculate a smoothness or ride quality index, the most common of which—the International Roughness Index (IRI)—is a performance measure that state departments of transportation (DOTs) must report to the Federal Highway Administration (FHWA) as part of Highway Performance Monitoring System/Moving Ahead for Progress in the 21st Century (HPMS/MAP-21) Act and Fixing America’s Surface Transportation (FAST) Act requirements. The information in this report can help ensure that accurate data are collected both for smoothness specifications at the project level and for MAP-21 Act and FAST Act requirements that the states provide accurate and consistent IRI data.

The report is accompanied by the following appendices:

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