California Profilograph

Ministry of TransportationMinistry of Transportation

Moving to International Roughness Index Measured By Inertial Profilers for Acceptance

of New Asphalt Construction in Ontario

By

John A. Blair, Bituminous EngineerKai K. Tam, Head

Bituminous SectionMinistry of Transportation of Ontario (MTO)

CUPGANovember, 2009

October 29, 2003 2Highway Standards Branch

Ministry of Transportation

California Profilograph



MTO’s Network Level Monitoring• Currently based on IRI, as measured by an

Automated Road Analyzer (or Aran).



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).



Investigation Main Objectives1) Determine if Inertial Profilers can produce

measurements comparable to California Profilographs;

2) Implement for acceptance of new HMA pavements, if is it found that:

a) IRI can be used to replace PI; and b) Inertial profilers can replace scallops with

some other attribute (i.e. “localized roughness”).



Some Issues InvolvedLaser 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.



ProVAL®• Developed by the Transtec Group in Texas.

• Can be downloaded free of charge from: www.RoadProfile.com

• Benefits of ProVAL® include:- - Accepts raw data files from various profilers

and simulates different indices (IRI, PI, RN etc.)

- - Produces more consistent results.



Investigation Conducted1) Measured several pavement sections to

compare inertial profilers equipped with laser arrays and profilographs;

2) Processed raw data files through ProVAL® to determine:a) IRI & “Localized Roughness”; andb) Correlation between IRI generated from the laser

arrays and PI reported by the operators of the profilographs.

3) Determined “equivalent” acceptance limits for:a) IRI to replace PI; andb) Localized roughness to replace scallops.



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.



IRI by Laser Arrays Versus PI(0) by Profilographs

0

0.5

1

1.5

2

2.5

0 200 400 600 800 1000

y = 0.19157 + 0.0019013x R= 0.95748 Current PI Acceptance Limits

Average PI(0) By Profilographs (mm/km)

Ave

rage

IRI b

y La

ser A

rray

s (m

/km

)

RejectablePriceReduced

Equivalent IRI Limits

Full PayBonus



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 < 0.65Full Payment 230 to 430 0.65 to 1.00

Price Reduction > 430 to 550 > 1.00 to 1.25Rejectable > 550 > 1.25

* Using ProVAL’s ® “Ride Stats at Intervals” Option



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.



Acceptance Limits for Scallops and Localized Roughness (Asphalt Only)

13

AcceptanceCategory

Current Limits for Scallops

(to the nearest 0.5 mm)

“Equivalent”Localized Roughness*

(to the nearest 0.05 mm)

Acceptable < 10.0 < 3.30Category 1

Price Reduction10.0 to 11.5 3.30 to 3.70

Category 2

Price Reduction12.0 to 14.5 3.80 to 4.70

Category 3

Rejectable > 14.5 > 4.70

* Using ProVAL’s ® “Localized Roughness (Tex-1001-s)” Option



Inertial Profiler Requirements (1)

14

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: ≤ 0.010 g (including all relevant

factors e.g. bias and scale, thermal sensitivity, non-linearity, noise etc.)



Inertial Profiler Requirements (2)

15

3)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.



IRI-Profiler Based Implementation

16

• 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.



QUESTIONS?

California Profilograph

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