1. Ride Specification – IRI Update Prepared by Joe Thomas, P.E. 11/1/06 MAAPT 53 rd Annual Asphalt Conference December 6, 2006

2. Why is ride important?

3. Our customers - the driving public values pavement smoothness very high

4. For most bituminous projects let prior to 2006, Profile Index was used to evaluate ride quality

5. During construction season 2006; the International Roughness Index (IRI) was used to evaluate ride.

6. When and Where did IRI originate? Developed in 1982 as part of a World Bank effort to establish correlation and calibration standards for roughness measurements.

7. Why did IRI originate? A standard road roughness measurement was required by the World Bank in order to loan money to Countries to build roads.

8. Why did IRI originate? Performance measure – What level of smoothness are we getting for our money?

9. Who uses IRI? FHWAs Highway Performance Monitoring System (HPMS), which tracks the condition of pavements nationwide.

10. Who uses IRI? Texas, South Dakota, New Mexico, Maryland, Pennsylvania, Michigan, Virginia, Montana, Connecticut, etc.

11. Who uses IRI? Europe - most widely used index to describe the roughness of highway pavements

12. What is IRI? A standardized roughness measurement It is based on a simulated suspension deflection of agolden car

13. International Roughness Index (IRI) Golden Car

14. Quarter car simulation used for IRI Source: Sayers and Karamihas 1998

15. What is IRI? The golden car travels approximately 50 mph over the roadway Always the same car and same suspension over different roadway profiles

16. How is IRI calculated? Think of IRI as simply the total distance a shock absorber travels vertically versus the distance a vehicle travels horizontally. IRI values are stated in inches/mile or m/km

17. International Roughness Index (IRI) IRI = 0 in/mi IRI = 95 in/mi It is a mathematical property of the profile of a single wheel path.

18. Why change from the Profile Index (P.I.) to the International Roughness Index (IRI)?

19. Why change from Profile Index to IRI? IRI values are well correlated to how ride feels in a car –Profile Index is not well correlated to how ride feels in a car

20. Why change from Profile Index to IRI? IRI uses the true profile of the road

22. Why change from Profile Index to IRI? Profile Index can show imaginery bumps because of profilograph geometry - Why a bump, dip, bump is considered one event

24. Why change from Profile Index to IRI? Less limitation on degree of vertical or horizontal curves - Dont drive so fast as to have accelerometer effects

25. Why change from Profile Index to IRI? You can get a range of IRI values for the same two-tenths blanking band value.

27. For example : 0.0 on the 0.2 bb can range from an IRI of 27* to an IRI of 42* inches/mile * Approx. values

28. Why change from Profile Index to IRI? Allows for valid QC/QA - results are reproducible using different machines within acceptable tolerances

29. Why change from Profile Index to IRI? Uniformity of a single measuring system – IRI value in South Dakota can mean the same as Minnesota provided parameters are the same

30. Additional benefits Less labor expense – Less time than traditional profilographing Safer –Eliminate or less traffic control to obtain measurements

31. If it says IRI; can we assume the values are always correct?

33. We have found that some software programs were incorrectly calculating the IRI values.

34. The following two machines do not calculate IRI.

35. California Profilograph (Truss Type)

36. California Profilograph (Beam Type)

37. Today, there are newer machines being used for measuring ride.

38. Lightweight Profilers

39. SSI © High Speed

40. Ames © High Speed Profiler

41. Pathways Pavement Van

42. What software will calculate IRI? Each IRI certified smoothness device will have its own software to calculate IRI? –Machine software must provide results within a certain tolerance of Mn/DOTs standard ProVAL – latest version 2.7 –Federal Highway Administration

43. University of Washington, Seattle, WA; Construction Engineering; Professor Joe Mahoney <60 inches/mile – most people cannot tell the difference - like the threshold of hearing

44. Think of IRI values in this context: < 32.0 inches/mile – no effect on vehicle operating costs <50.0 inches/mile – reduced vehicle operating costs <63.4 inches/mile – standard vehicle cost <95.0 – increased vehicle costs

45. Can you answers these questions? How wide is four rods of right of way? What year did a man land on the moon? What is the name of the currency used in India? 66 feet 1969 Rupee

46. Why/how did you know the answers? Experience –Active participation in events or activities, leading to the accumulation of knowledge or skill –An event or series of events participated in or lived through –The totality of such events in the past of an individual or group

47. Can you answer these questions about IRI? Is an IRI of 100 inches per mile a good ride value for a three lift bituminous pavement? Is an IRI of 25 inches per mile a good ride value? Is an IRI 5 inches per mile a realistic ride value? No Yes No

48. Can you answer these questions about IRI? What range of values are typically for: – a three lift project? – two lift project? –one lift project?

49. What are typical IRI values? 3- Lift Construction –Three lifts over concrete (10.4 mi project): 37.5 in/mile –Reconstruction; three lifts (5.2 mi project): 39.0 in/mile 2- Lift Construction –Mill and two lifts (10.0 mi project): 49.6 in/mile 1- Lift Construction –Single lift with patching (7.8 mi project): 55.8 in/mile

50. MN/DOT Bituminous Specifications provide the contractor an opportunity to receive an incentive or disincentive payment. The payment is based on an International Roughness Index (IRI) value and whether that segment contains any bumps and/or dips.

51. What happened using IRI in 2006? The 2006 bituminous specification required smoothness evaluation using the International Roughness Index (IRI)

52. IRI Equations A, B and C (graphed)

53. Impact to Incentive/disincentive dollars? For 652, 0.1 mile segments –Equation A - $215,800 –Table A - $194,245

54. Impact to Incentive/disincentive dollars? For 195, 0.1 mile segments –Equation B - $19, 325 –Table B- $17,475

55. Incentive/disincentive dollars? For 635, 0.1 mile segments –Equation C - $58,075 –Table C - $69,650 IRI Equation C pays approximately $0.83 dollars for every $1.00 dollar of Profile Index

56. 2007 Smoothness Device Certification will be held at MnRoad, Albertville, MN

57. 2007 Certificates will be yellow!!

58. For the 2007 Construction Season Four IRI ride specifications –IRI Equation A – replaces Table A –IRI Equation B – replaces Table B –IRI Equation C – replaces Table C –IRI Percent Improvement – predominately for application on single lift overlays where the existing IRI is greater than 120 in/mile

59. Smoother roads last longer. Any questions of us? Thank you