Ministry of Transportation Moving to International Roughness Index Measured By Inertial Profilers...
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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 3Highway Standards Branch
Ministry of Transportation
MTO’s Network Level Monitoring• Currently based on IRI, as measured by an
Automated Road Analyzer (or Aran).
October 29, 2003 4Highway Standards Branch
Ministry of Transportation
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).
October 29, 2003 5Highway Standards Branch
Ministry of Transportation
Investigation Main Objectives
1) 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”).
October 29, 2003 6Highway Standards Branch
Ministry of Transportation
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.
October 29, 2003 7Highway Standards Branch
Ministry of Transportation
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.
October 29, 2003 8Highway Standards Branch
Ministry of Transportation
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”; and
b) 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; and
b) Localized roughness to replace scallops.
October 29, 2003 9Highway Standards Branch
Ministry of Transportation
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.
October 29, 2003 10Highway Standards Branch
Ministry of Transportation
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
rag
e IR
I b
y L
aser
Arr
ays
(m/k
m)
RejectablePriceReduced
Equivalent IRI Limits
Full PayBonus
October 29, 2003 11Highway Standards Branch
Ministry of Transportation
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
October 29, 2003 12Highway Standards Branch
Ministry of Transportation
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.
October 29, 2003 13Highway Standards Branch
Ministry of Transportation
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
October 29, 2003 14Highway Standards Branch
Ministry of Transportation
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.)
October 29, 2003 15Highway Standards Branch
Ministry of Transportation
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.
October 29, 2003 16Highway Standards Branch
Ministry of Transportation
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.