# Presentation: 676820

## HPMS IRI

- <date/time>

**HPMS IRI**

- Highway Information Seminar
- Rosslyn, VA
- November 17, 2004

## HPMS IRI Data

- Uses of IRI Data
- Why IRI?
- HPMS IRI observations
- Improving IRI

**Notes:**
I will try to provide some insight into FHWA’s uses of IRI data and why FHWA uses the IRI statistic and not some other measure;

I will also show you some reporting statistics that will give you an idea of how much system level IRI data are being reported to the HPMS by the States and describe a technique, still under development, to indicate the apparent currency of the data.

I will also talk briefly about some FHWA perceptions of what can be done to improve the quality of reported IRI data.

## Uses of IRI Data

- National pavement needs
*Status of the Nation’s Highways, Bridges, and Transit: Conditions & Performance*
- Performance of the NHS
- Above uses can be  referenced at: **www.fhwa.dot.gov**
- Performance of the STRAHNET
- Other studies

**Notes:**
The principal use of IRI data is to enable the FHWA to estimate future pavement needs for the mandated biennial Conditions and Performance report to Congress.  The next one of these will be produced next year using 2002 data.

IRI data, while not a true measure of pavement condition, are used in this context only as a baseline indicator of pavement condition.  Using current and estimated future traffic and truck loadings, also from the HPMS, current pavement condition is deteriorated and an estimate of future replacement needs and costs is made.  The aggregate numbers are provided to Congress and used to establish funding levels for future Federal-Aid Highway Programs. 

Performance goals are required by the Congress as a condition of continued funding for the Federal-aid Highway Program, and IRI data are used as a measure of the performance of the NHS.  Through customer surveys, FHWA has determined that pavement smoothness is a highly significant user concern and established a pavement smoothness performance goal for the NHS including all of its intermodal connectors.

The STRAHNET includes the Interstate highways and a subset of the remaining NHS designated to serve military mobility needs.  The IRI has been selected as an indicator of pavement condition for these routes that provide for our national security needs.

FHWA also uses these data in Congressionally mandated truck size and weight and cost allocation study activities to estimate the impacts of heavy vehicles on pavement needs and costs.  These studies are used to set national policy on truck size and weight and to evaluate various policies.  As I speak, a research effort is underway to improve the pavement deterioration and cost allocation models that FHWA uses based in part on IRI data.  It is quite possible that in the future, FHWA will begin acquiring additional and more detailed pavement-related data items in the HPMS to support these models.  As far as I know however, IRI will remain on the FHWA radar screen.

Finally, there are many other public, private, and research entities that are interested in HPMS IRI data.

## Why IRI?

- Objective
- Instrument-based
- Science-based
- Easily measured

**Notes:**
The IRI was selected by a panel of State data providers working with the FHWA as a more objective pavement indicator than the previously used Present Serviceability Rating (PSR).  It relies on a measured profile instead of on a visual evaluation and is somewhat subjective and prone to distortion based upon the background, experience, and training of the raters.

IRI is instrument-based and the input devices can therefore be calibrated and the data subjected to a standard accumulation and reduction procedure.

A profile is science-based and can therefore (within reason) be expected to mean the same thing across the country.  Measurement consistency is an issue, but FHWA feels that the “bandwidth” of variability will steadily improve over time as IRI is currently the best measure of pavement performance and smoothness.

And, as far as objective data collection goes, it is easily measured at a system level, usually only requiring the ability to drive the roadway at speed.

## IRI Data Reporting Requirements:

- All Interstate sections
- All Freeway and Other Principal Arterial sections
- All rural minor arterial _sample_ sections
- All NHS sections
- All STRAHNET sections

## Highway System (2003)

**Highway System (2003)**

- non-Interstate

- non-Interstate

**Notes:**
This slide shows percent of miles with IRI data reported in the HPMS for the required systems.

As you can see, the highest level of reporting is on the Rural systems, and most urban systems are reported in the upper 90% range.  Reporting has improved on the Urban Other Principal Arterial system is generally less complete and is an area of focus for FHWA.  However, there has been noted improvement in the reporting of IRI data for this system in 2003 as compared to previous years (I think it was at 78% in 2002) and we are hopeful that future data will be virtually complete as a result of newer devices are acquired by the States and technological improvements are made to overcome the difficulty in measuring some sections.

##  Updating HPMS IRI

- Equal IRI values over time
- Matched sample analysis
- Programmatically matches sections over time
- Conservative estimate of severity
- GIS analysis
- Map-based matching of sections over time
- Utilizes NHPN GIS files with HPMS data
- Closer estimate of severity

**Notes:**
Two methods have been used to help evaluate IRI data submitted to FHWA, one of which is still under development.  Both assume that identical roadway sections coded with identical IRI values over a period of more than 2 years represents un-updated IRI data.  Needless to say, this can and does occur in some States.  Our analysis of these data over time even seem to indicate some unchanged IRI data on the same sections of roadway going back several years– even back to 1993!

It would appear that although most of the IRI data system coverage in HPMS are complete, a significant amount does not appear to be current within the last 2 years.  FHWA is concerned about the possible impact this may have on national level statistics and trends and thus is where the current focus is re: IRI rather than completeness of reporting.

The first method is a matched sample analysis: this involves using a simple program to match identical HPMS sample sections and finding identical IRI values between the years of interest.  (Sample ID is a permanent identifier code in HPMS that does not change over time).  This basically gives us a conservative estimate of un-updated IRI on sample sections only but is indicative of possibly more extensive un-updated data on other universe sections.

The second is a GIS analysis technique using the National Highway Planning Network (NHPN) – a base GIS network consisting of the principal arterial, rural minor arterial, NHS, and STRAHNET roadway sections.  Again, HPMS requires IRI reporting on all of these systems with the exception of only samples needed on the rural minor arterials.  HPMS data item attributes and geo-coding are then dynamically segmented to the NHPN and can contain multiple years of data, if desired.   This gives us a more extensive view of unchanged IRI data that goes beyond just sample sections and allows us to see what’s occurring at a system level.  All of this depends on a well-maintained and properly geo-coded network.

##  Updating HPMS IRI

- Equal IRI values over time
- Data not being collected/reported
- Data collected but not reported
- Translation error/technical difficulties
- Requires communication and action to resolve

## 2003

**2003**

**2001**

- Sample “123ABC”

- IRI=98 in/mi

- Etc...

- IRI=98 in/mi

- Sample
- “456DEF”

- IRI=102 in/mi

- IRI=90 in/mi

**2003**

**2001**

- Etc...

- IRI=98 in/mi

- IRI=98 in/mi

- IRI=98 in/mi

- IRI=98 in/mi

- IRI=124 in/mi

- IRI=124 in/mi

- IRI=133 in/mi

- IRI=133 in/mi

**Notes:**
Explain figure...

Matched sample process vs. GIS.

More matches indicated via the GIS analysis.

## Slide 10

**Notes:**
Explain map...  (Credit Tom Roff for production assistance).

Caveats: Note that for AR, MA, and WA we had difficulties in the network files or attaching HPMS data to them.  2002 data shown for MO as they have not submitted 2003 data as yet.  Also, the rural minor arterial functional system is shown in its entirety whereas IRI is only required in HPMS on the sample sections of this system.  This map should serve to illustrate the concept rather than illustrate data deficiencies as it is a work in progress, and there may be some inaccuracies for some States.  (2002 data may have been accidentally used instead of 2001 for some States).

For the sections showing identical IRI values between 2001 and 2003, it appears either the data has not been collected or the data has been collected but is not being reported in HPMS due to an internal processing problem.

This is an example of how we can look at the network IRI data by screening out just the Interstate or some other functional system requiring IRI, or by ownership category, or just the NHS.  State vs. off-State system IRI data being reported in HPMS has been a historical issue, for example.

## Improving HPMS IRI Reporting

- AASHTO PP 37-02 (new -04)
*HPMS Field Manual*
- Appendix E (see above)
- HPMS CBT
- 2-year reporting cycle
- Documented procedures
- QA/QC program / CPI model
- Link HPMS to PMS

**Notes:**
For the sake of consistency and data comparability at the National level, FHWA has adopted the AASHTO provisional standard as the basis for reporting IRI data to the HPMS.
Various other reporting requirements are included in its HPMS Field Manual  and CBT that impact the processing and reporting of IRI data to the HPMS.  The elimination from the profile of localized discontinuities such as bridge decks and approaches and railroad crossings before computing an IRI value for HPMS from the profile is requested, for example.

We also ask that HPMS IRI data be collected and reported within a 2-year cycle for all required roadway sections, and that older data be left coded in place until updated data is measured.

States should have strong documentation for the data collection, reduction, and reporting processes used to generate IRI values.  We believe that these are essential for State personnel when the State obtains data under contract or when the State requires other governmental units, such as cities and counties, to provide these data.

Likewise, States should have documented QA/QC procedures in place to assure that those collecting and reporting IRI data are providing a quality product.  Recently, FHWA has been promoting the Continuous Process Improvement (CPI) model to enhance the quality of priority HPMS data items like IRI.

Finally, we recommend that data collected for the State’s PMS be used to populate the HPMS to the greatest extent possible.  We subscribe to the “collect it once, use it often” management philosophy and believe that there may be opportunities to streamline and economize the process.

Good news: we’ve seen improvement in the completeness of IRI data reporting, but appears more attention may be needed in the area of updating IRI within the 2-year minimum cycle.  And as we refine a GIS technique, we hope it may be of value to our State data providers in the future.  Questions?