1. Safety Benefits of Permeable Friction Course?
Statistics in Water Resources
Brad Eck
April 30, 2009

2. Permeable Friction Course
Safety Benefits of PFC
Removes water from the road surface
Reduced splash and spray
Drainage through the pavement rather than across it
Does this result in fewer crashes?
Permeable Friction Course

3. Data Sources Texas Peace Officer’s Crash Report (compiled by TxDOT)
Traffic Counts from Capital Area Metropolitan Planning Organization (CAMPO)
Rainfall history at Bull Creek & Loop 360 from Lower Colorado River Authority (LCRA)

4. Near Spicewood Springs
Loop 360
Bull Creek
Gauging Station
Near Spicewood Springs
Black –eyed Susan

5. Annual Crash Statistics – Entire Highway
PFC Installed September 2004

6. Roadway Segment & Surface Condition
Most crashes occurred under dry conditions
Consistent with statewide analysis
PFC section showed more variability
PFC Installed

7. Crashes in Wet Conditions
Hypothesis Tests on PFC (north) and Impervious (South)
Conclusion: PFC did not help on this roadway
F-Test
T-Test
Test Statistic
0.812
0.54
P-value
0.39
0.30
F-Test
T-Test
Test Statistic
0.223
0.65
P-value
0.07
0.28

8. Remaining Work
Compare wet/dry classifications with precipitation record at Bull Creek
Precipitation Intensity
Examine other contributing factors