presented by: kelly l. smith, applied pavement …...2008 ohio friction study aptech staff • roger...
TRANSCRIPT
![Page 1: Presented by: Kelly L. Smith, Applied Pavement …...2008 Ohio Friction Study APTech Staff • Roger Larson • Todd Hoerner • Kurt Smith • Angela Wolters ODOT Liaisons • Andrew](https://reader034.vdocuments.mx/reader034/viewer/2022050118/5f4e7c81b6f9633f2c3bdb7a/html5/thumbnails/1.jpg)
Presented by:
Kelly L. Smith, Applied Pavement Technology Inc. (APTech)
Roger M. Larson, Retired (formerly APTech and FHWA)
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2008 Ohio Friction Study
APTech Staff
• Roger Larson
• Todd Hoerner
• Kurt Smith
• Angela Wolters
ODOT Liaisons
• Andrew Williams
• Roger Green
• Brian L. Schleppi
• Thad Tibbles
• Valerie Webb
![Page 3: Presented by: Kelly L. Smith, Applied Pavement …...2008 Ohio Friction Study APTech Staff • Roger Larson • Todd Hoerner • Kurt Smith • Angela Wolters ODOT Liaisons • Andrew](https://reader034.vdocuments.mx/reader034/viewer/2022050118/5f4e7c81b6f9633f2c3bdb7a/html5/thumbnails/3.jpg)
Ohio Safety Efforts
• Developed base crash rates for intersections and freeways to help identify those with higher-than-average rates
• Developed crash reduction factors for various countermeasures
• Implemented a significant road safety audit (RSA) program
• Undertaken major research on friction qualities of various aggregates
• Participated in FHWA’s Highway Safety Information System (HSIS)
• Consistently reduced highway fatality rates, as well as the number of fatalities.
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Ohio 2006 Safety Goals
Refine, refocus and respond to high crash
locations
• Reduce crash frequency by 10% by 2015
• Reduce rear-end crashes by 25% by 2015
• Reduce state fatality rate to 1.0 fatality per 100
MVMT by 2008
• Reduce annual fatalities to 1100 by 2008
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Research Objectives
• Determine if a correlation exists between
locked-wheel friction (FN) and wet pavement
crashes and, if so:
• which test tire (ribbed or smooth) is more correlated.
• what the desirable or target FN values should be for
different site categories / friction demand categories.
• Develop improved guidance on use of ribbed
versus smooth tires and provide
recommendations regarding minimum friction
numbers for each type.
![Page 6: Presented by: Kelly L. Smith, Applied Pavement …...2008 Ohio Friction Study APTech Staff • Roger Larson • Todd Hoerner • Kurt Smith • Angela Wolters ODOT Liaisons • Andrew](https://reader034.vdocuments.mx/reader034/viewer/2022050118/5f4e7c81b6f9633f2c3bdb7a/html5/thumbnails/6.jpg)
Research Approach
• Task 1. Literature Review
• Task 2. Design Experiment
• Task 3. Collect Data
• Task 4. Develop Correlations
• Task 5. Recommend Friction Numbers
• Task 6. Final Report
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Task 1. Literature Review Conclusions
• Friction/texture is an important surrogate for
safety.
• Greater attention to engineering safer roads
can potentially reduce fatalities and serious
injuries by a considerable amount.
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Task 2. Design Experiment Site Selection, Crash and Inventory Data
• 90 sites selected covering three categories
• congested freeways: 30
• signalized intersections: 30
• unsignalized intersections: 30
• For each category,
• low wet/total crash ratio (0.15): 10
• medium ratio (0.15 to 0.35): 10
• high ratio (>0.35): 10
• Representation across Districts, pavement types
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Task 3. Collect/Compile Data
• ODOT provided: • Comprehensive inventory and pavement condition data.
• Crash data for 2003-2005.
• Field testing by ODOT in summer/fall of 2007.
• At each of the 90 selected sites: • Friction tests at 40 mph and one other speed (20 mph for
intersections, 60 mph for freeways) with both ribbed and smooth tire (using two ODOT locked-wheel friction trailers)
• Macrotexture measurements using a high-speed laser profiler (85 of 90 sites) (MPD later converted to MTD)
• Develop analysis database (spreadsheet)
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Task 4. Develop Correlations Data Analysis
• Develop plots of friction and texture statistics
versus crash statistics for the 90 sites.
Dependent Variable
• Total crashes
• Wet/total crash ratio
• Rear-end crash rate
Independent Variable
• FN40Ravg
• FN40Rmin
• FN40Savg
• FN40Smin
• FN20Ravg or FN60Ravg
• FN20Rmin or FN60Rmin
• MTDavg
• MTDmin
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Task 4. Develop Correlations Example Analysis Plot
Wet/Total Crash Ratio vs. FN40 (Avg and Min) for All Sections
(Ribbed and Smooth Tires)
y = -0.2597Ln(x) + 1.1916
R2 = 0.1712
y = -0.2566Ln(x) + 1.1644
R2 = 0.181
y = -0.1578Ln(x) + 0.7693
R2 = 0.0697
y = -0.1422Ln(x) + 0.7038
R2 = 0.0673
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
10 20 30 40 50 60 70
FN40
Wet/
To
tal
Cra
sh
Rati
o
FN40R Avg.
FN40R Min.
FN40S Avg.
FN40S Min.
Log. (FN40R Avg.)
Log. (FN40R Min.)
Log. (FN40S Avg.)
Log. (FN40S Min.)
FN40R Avg:
FN40R Min:
FN40S Avg:
FN40S Min:
FN40
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Task 4. Develop Correlations Example Cumulative % Crashes Plot
Cumulative % of All Crashes (in Test Direction) Observed on
Congested Freeways vs. FN40 for Ribbed and Smooth Tires
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75
FN40
Cu
mu
lati
ve
% o
f A
ll C
ras
hes
(in
Te
st
Dir
ec
tio
n)
Ob
se
rve
d o
n C
on
ge
ste
d F
ree
wa
ys
Ribbed Tire
Smooth Tire
377 total crashes were observed in the test
direction for sections included in this analysis
FN40
42 34
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Task 5. Recommend Friction Numbers Cumulative % Crashes vs. FN Results
% of
Total
Crashes
Congested Freeways
Signalized
Intersections
Unsignalized
Intersections
FN40Savg FN40Ravg FN40Savg FN40Ravg FN40Savg FN40Ravg
90 < 30 < 42 < 29 < 42 < 40 < 50
85 < 29 < 40 < 27 < 39 < 37 < 47
50 < 26 < 34 < 21 < 30 < 29 < 39
15 < 23 < 33 < 14 < 27 < 24 < 32
10 < 22 < 32 < 13 < 17 < 23 < 26
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Task 6. Final Report
Key Findings • No single variable (ribbed tire, smooth tire,
macrotexture) correlates highly with crashes
for each site category
• FN40Ravg/FN40Rmin better correlated than
FN40Savg/FN40Smin
• FNmin quite consistent and usually ~2
percentage points below FNavg
• For congested freeways, rear-end crash rate
drops significantly at MTD ~1.0 to 1.2 mm
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Task 6. Final Report
Key Recommendations
• Continue use of FN40R
• Use New York SKARP approach for setting
investigatory and intervention levels
• 3-prong check of wet/total crash ratio, total
crashes (annual), and friction
• Supplement with macrotexture check
• Establish levels for 3-5 site categories (per
AASHTO Guide for Pavement Friction)
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Thank You!!
Kelly Smith, Sr. Engineer
Applied Pavement Technology, Inc.
Roger M. Larson, Retired
Applied Pavement Technology, Inc.