Ministry of Transportation Moving to International Roughness Index

Ministry of Transportation 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

Ministry of Transportation California Profilograph Highway 2003 October 29, Standards Branch 2

Ministry of Transportation MTO’s Network Level Monitoring • Currently based on IRI, as measured by an Automated Road Analyzer (or Aran). Highway 2003 October 29, Standards Branch 3

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). Highway 2003 October 29, Standards Branch 4

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”). Highway 2003 October 29, Standards Branch 5

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 Pro. VAL® is now available. Highway 2003 October 29, Standards Branch 6

Ministry of Transportation Pro. VAL® • Developed by the Transtec Group in Texas. • Can be downloaded free of charge from: www. Road. Profile. com • Benefits of Pro. VAL® include: - - Accepts raw data files from various profilers and simulates different indices (IRI, PI, RN etc. ) - - Produces more consistent results. Highway 2003 October 29, Standards Branch 7

Ministry of Transportation Investigation Conducted 1) Measured several pavement sections to compare inertial profilers equipped with laser arrays and profilographs; 2) Processed raw data files through Pro. VAL® 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. Highway 2003 October 29, Standards Branch 8

Ministry of Transportation Data Analysis and Reporting - IRI vs PI • Raw data files from the laser arrays ran through Pro. VAL® 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. Highway 2003 October 29, Standards Branch 9

Ministry of Transportation Average IRI by Laser Arrays (m/km) IRI by Laser Arrays Versus PI(0) by Profilographs Bonus Full Pay Price Rejectable Reduced Equivalent IRI Limits Current PI Acceptance Limits Average PI(0) By Profilographs (mm/km) Highway 2003 October 29, Standards Branch 10

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” IRIbased 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 Pro. VAL’s ® “Ride Stats at Intervals” Option Highway 2003 October 29, Standards Branch 11

Ministry of Transportation Data Analysis and Reporting Localized Roughness vs. Scallops • Ran raw data files through Pro. VAL® 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. Highway 2003 October 29, Standards Branch 12

Ministry of Transportation Acceptance Limits for Scallops and Localized Roughness (Asphalt Only) Acceptance Category Acceptable Category 1 Price Reduction Category 2 Price Reduction Category 3 Current Limits for Scallops (to the nearest 0. 5 mm) “Equivalent” Localized Roughness* (to the nearest 0. 05 mm) < 10. 0 < 3. 30 10. 0 to 11. 5 3. 30 to 3. 70 12. 0 to 14. 5 3. 80 to 4. 70 > 14. 5 > 4. 70 Rejectable * Using Pro. VAL’s ® “Localized Roughness (Tex-1001 -s)” Option Highway 2003 October 29, Standards Branch 13

Ministry of Transportation Inertial Profiler Requirements (1) 1) Laser Sensors (dual sensors at 2 m spacing) • Footprint: ≥ 70 mm width • Sampling Rate: ≥ 3 k. Hz • 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. ) Highway 2003 October 29, Standards Branch 14

Ministry of Transportation Inertial Profiler Requirements (2) 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. Highway 2003 October 29, Standards Branch 15

Ministry of Transportation 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. Highway 2003 October 29, Standards Branch 16

Ministry of Transportation QUESTIONS? Highway 2003 October 29, Standards Branch 17