Why is ride important?

Our customers - the driving public values pavement smoothness very high

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.

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

Impact to Incentive/disincentive

dollars?•For 652, 0.1 mile segments

–Equation A - $215,800–Table A - $194,245

Impact to Incentive/disincentive

dollars?•For 195, 0.1 mile segments

–Equation “B” - $19, 325–Table B - $17,475

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

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

2006 Initial Certification Results on Bituminous Test Section:IRI Percent Deviation from Walking Profiler

-10%

-5%

0%

5%

10%

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Roughness Measuring Apparatus

IRI P

erce

nt D

evia

tion

from

W

alki

ng P

rofil

er

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

2007 Certificates will be yellow!!

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

IRI Equations A, B and C (graphed)

Possible changes for the 2008 Construction

Season• Speed limit change to less than 42 mph

– Currently less than 50 mph

• IRI in both the right and left wheelpaths– Currently right wheelpath only

• Segments to be pro-rated on actual length– Currently segments greater than 250 feet

treated the same

Possible changes for the 2008 Construction

Season• Specification written for 0.1609km or 0.1

miles– now references to 100m or 0.1 miles

• Areas of localized roughness to replace bumps and dips

• Operator certification – Use of Proval xx.xx to determine areas of

localized roughness

• Smoother roads last longer.

• Any questions of us?

• Thank you