1. Moving to International Roughness Index Measured By Inertial Profilers for Acceptance of New Asphalt Construction in Ontario By
John A. Blair, Bituminous Engineer Kai K. Tam, Head Bituminous Section Ministry of Transportation of Ontario (MTO)
CUPGA
November, 2009

2. California Profilograph

3. MTO’s Network Level Monitoring
Currently based on IRI, as measured by an Automated Road Analyzer (or Aran).

4. Issues With Existing System
Smoothness acceptance for new asphalt pavements is based on PI but network level measurements based on IRI.
California Profilographs:
- Take measurements at 3 to 5 km/hr (i.e. require traffic protection);
- Measure one wheelpath at a time;
- On the road for long periods of time (i.e. leads to safety concerns).

5. Investigation Main Objectives
Determine if Inertial Profilers can produce measurements comparable to California Profilographs;
Implement for acceptance of new HMA pavements, if is it found that:
IRI can be used to replace PI; and
Inertial profilers can replace scallops with some other attribute (i.e. “localized roughness”).

6. Some Issues Involved Laser Sensors Footprint:
Most inertial profilers use single dot laser sensors.
Single dot lasers have accuracy/repeatability issues on open-graded mixes;
New multiple laser arrays have been developed (Rolines use 100 laser dots, triods use 3 laser dots).
Software – Data Analysis:
Each manufacturer currently use their own software & methods of data filtering to calculate & report IRI.
New software program called ProVAL® is now available.

7. ProVAL® Developed by the Transtec Group in Texas.
Can be downloaded free of charge from:
Benefits of ProVAL® include:
- Accepts raw data files from various profilers and simulates different indices (IRI, PI, RN etc.)
- Produces more consistent results.

8. Investigation Conducted
1) Measured several pavement sections to compare inertial profilers equipped with laser arrays and profilographs;
Processed raw data files through ProVAL® to determine:
IRI & “Localized Roughness”; and
Correlation between IRI generated from the laser arrays and PI reported by the operators of the profilographs.
3) Determined “equivalent” acceptance limits for:
IRI to replace PI; and
Localized roughness to replace scallops.

9. Data Analysis and Reporting - IRI vs PI
Raw data files from the laser arrays ran through ProVAL® using its “Ride Stats at Intervals” option to determine IRI.
The combined average IRI determined from the laser arrays was plotted against the combined average PI reported by the operators of the profilographs.

10. IRI by Laser Arrays Versus PI(0) by Profilographs
Bonus
Full Pay
Rejectable
Price
Reduced
Average IRI by Laser Arrays (m/km)
Equivalent IRI Limits
Current PI Acceptance Limits
Average PI(0) By Profilographs (mm/km)

11. Acceptance Limits for PI and IRI (Asphalt Only)
Payment Category
Current PI-Based Limits (0 blanking band)
to the nearest 2 mm/km
“Equivalent” IRI-based Limits*
to the nearest 0.05 m/km
Maximum Bonus
< 150
< 0.50
Bonus
150 to < 230
0.50 to < 0.65
Full Payment
230 to 430
0.65 to 1.00
Price Reduction
> 430 to 550
> 1.00 to 1.25
Rejectable
> 550
> 1.25
* Using ProVAL’s ® “Ride Stats at Intervals” Option

12. Data Analysis and Reporting - Localized Roughness vs. Scallops
Ran raw data files through ProVAL® using:
- “Localized Roughness (i.e Tex-1001-s)” option; and
- Several different threshold limits were assumed.
Used an iterative process to determine limits for localized roughness that was determined to be most “Equivalent” to the limits for MTO’s 3 acceptance categories for scallops.

13. Acceptance Limits for Scallops and Localized Roughness (Asphalt Only)
Category
Current Limits for Scallops
(to the nearest
0.5 mm)
“Equivalent”
Localized Roughness*
0.05 mm)
Acceptable
< 10.0
< 3.30
Category 1
Price Reduction
10.0 to 11.5
3.30 to 3.70
Category 2
12.0 to 14.5
3.80 to 4.70
Category 3
Rejectable
> 14.5
> 4.70
* Using ProVAL’s ® “Localized Roughness (Tex-1001-s)” Option 13

14. Inertial Profiler Requirements (1)
Laser Sensors (dual sensors at 2 m spacing)
Footprint: ≥ 70 mm width
Sampling Rate: ≥ 3 kHz
Sampling Interval: ≤ 25.4 mm
Resolution: ≤ 0.05 mm
2) Accelerometers
Range: ± 2 g to ± 3 g (assuming 1 g gravity bias is accounted for)
Accuracy: ≤ g (including all relevant factors e.g. bias and scale, thermal sensitivity, non-linearity, noise etc.) 14

15. Inertial Profiler Requirements (2)
Carrier
Dedicated vehicle
Speed: ≥ 60 km/hr
Offset Device:
Projected laser dot, video camera etc. to maintain ± 150 mm offset
GPS with 1 m accuracy
Flashing light (for safety purposes)
4) Software
Auto start/stop (to detect roadside markers)
Audible warning when sensors cease functioning or are out of acceptable range. 15

16. IRI-Profiler Based Implementation
Developed Non-Standard Special Provision (i.e. NSSP) for acceptance based on inertial profilers.
Developed equipment requirements and procedure for determining IRI and localized roughness based on raw data files obtained from inertial profilers.
Currently Implementing an IRI-based specification for new asphalt paving work. 16

17. QUESTIONS?