overview of the fhwa pavement friction management program virginia polytechnic institute and state...
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Overview of the FHWA Pavement Friction Management Program
Virginia Polytechnic Institute and State UniversityCharles E. Via Jr. Department of Civil Engineering
Edgar de León Izeppi
Outline
Development and Demonstration of Pavement Friction Mgt. Programs:
(FHWA DTFH61-09-R-00035)
ObjectivesBackgroundResearch TeamResearch Plan Phase I & IIApproaches for friction threshold level
Center for Sustainable Transportation Infrastructure
Objectives (4 states)
Determine criteria and methods, for investigatory (desirable) level and intervention (minimum) levels for friction and macro-texture for different demand/classes of highways.
Assist in developing PFM Programs.Demonstrate state-of-the-art friction
(and macro-texture) measurement equipment.
Center for Sustainable Transportation Infrastructure
Background
Goal: Reduce crashes (& fatalities) Evaluate recommendations of the
2008 AASHTO Guide for Pavement Friction.
Major strategy is to determine investigatory/intervention threshold values, based on analysis of crash data & determine friction and/or macrotexture requirements
Center for Sustainable Transportation Infrastructure
Center for Sustainable Transportation Infrastructure
FHWA COTR
Gerardo Flintsch (VTTI)Principal Investigator
Kelly Smith (APTech)Research Team Leader
Edgar de Leon (VTTI)Equipment Team Leader
Gerardo FlintschPFM Program Team Leader
Todd Hoerner (APTech)Database Developer/ Data Analyst
Feng Guo (VTTI)Statistician/ Safety Analyst
Roger Larson (APTech)Technical Advisor
William Hobbs (VTTI)Equipment Operator
Kurt Smith (APTech)Technical Advisor/ Project QA/QC
James Krstulovich (APTech)Data Collector/Data Analyst
Alejandra Medina (VTTI)Safety Analyst
Kevin McGhee (VTRC)Implementation Leader
James Wambold (CDRM)Technical Advisor
Kelly Smith (APTech)Co-Principal Investigator
Helen Viner (TRL)Program Developer
Peter Roe (TRL)Program Developer
James Krstulovich (APTech)Equipment Operator (as needed)
Tony Parry (TRL/UoN)Technical Expert
Center for Sustainable Transportation InfrastructureSource: International Road Traffic and Accident Database (IRTAD)
Demonstrate state-of-the-art friction (and macro-texture) measurement equipment
Center for Sustainable Transportation Infrastructure
Source: Delane (2005)
Friction measurement equipment
Center for Sustainable Transportation Infrastructure
1 Effectiveness in the prediction of (fatal) crash potential 2 Continuous friction measurement capability and operating
principle 3 Macrotexture measurement 4 Stage of development of the device (experimental or
commercially available) 5 Robustness and readiness for deployment 6 Data collection productivity 7 Measurement speed 8 Precision (Repeatability and Reproducibility) 9 Global Positioning System (GPS) 10 Software
Evaluation Criteria
1) Effectiveness predicting fatal crashes2) Continuous measurement principle
a) % Slip ratio (or equivalent)b) Type of tirec) Tire pressure (psi)d) Left-wheel path tiree) Right-wheel path tire possible
3) Macrotexture measurementa) Speed (kHz) b) Sampling distance
4) Commercially available5) Robustness and readiness for deploy
a) One operator capableb) Left side steering wheel availablec) Complete package from supplierd) Vertical load (lbs.)e) Dynamic vertical load sensor
Center for Sustainable Transportation Infrastructure
Evaluation Criteria (cont.)
6) Data collection productivitya) Typical water tank capacity (gallons)b) Range per tank (miles)
7) Measurement speed (recommended)a) Minimum/Maximum (mph/mph)
8) Precisiona) Repeatabilityb) Reproducibilityc) Length for the mean value (feet)
9) GPS-capable10) Highway Software available11) Other
a) Highway track record (number of devices in use)b) Delivery time (months)c) Cost of the 2 year technical support and maintenance agreement
Center for Sustainable Transportation Infrastructure
Different Approaches for setting investigatory (desirable) level and intervention (minimum)
levels for friction and macro-texture
Center for Sustainable Transportation Infrastructure
AASHTO Guide GPF friction threshold method
Center for Sustainable Transportation Infrastructure
Pavement Age, years
F(6
0),
Sp
or
FN Investigatory Level
Intervention Level
Friction
Pavement Age, years
F(6
0),
Sp
or
FN Investigatory Level
Intervention Level
Friction
Pavement Age, years
F(6
0),
Sp
or
FN Investigatory Level
Intervention Level Cra
sh
Ra
tes
Friction
Crash Rates
Pavement Age, years
F(6
0),
Sp
or
FN Investigatory Level
Intervention Level Cra
sh
Ra
tes
Friction
Crash Rates
F(60) ,Sp or FN
Nu
mb
er
of
Sit
es
We
t to
Dry
Cra
sh
es
, %
InterventionLevel
InvestigatoryLevel
Wet to DryCrashes
Mean – X*(Std Dev)
Mean – Y*(Std Dev)
F(60) ,Sp or FN
Nu
mb
er
of
Sit
es
We
t to
Dry
Cra
sh
es
, %
InterventionLevel
InvestigatoryLevel
Wet to DryCrashes
Mean – X*(Std Dev)
Mean – Y*(Std Dev)
Alternative ApproachesE.g., Model the probability of wet crash
as a function of friction number using logistic regression
Center for Sustainable Transportation Infrastructure
10 20 30 40 50 60 70 800
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16Estimated Probabilty of Accident with Confidence Interval
FN
Pre
dic
ted
Pro
ba
bilt
y
Center for Sustainable Transportation Infrastructure
0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65
A Motorway
B Dual carriageway non-event
C Single carriageway non-event
QApproaches to and across minor and major junctions, approaches to roundabouts
KApproaches to pedestrian crossings and other high risk situations
R Roundabout
G1 Gradient 5-10% longer than 50m
G2 Gradient >10% longer than 50m
S1 Bend radius < 500m - dual carriageway
S2 Bend radius < 500m - single carriageway
Investigatory level (50 km/h)Site category and definition
Investigatory Levels (UK)
Center for Sustainable Transportation Infrastructure
0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65
A Interstate highways
B Divided highways w/o intersections
C Two lane road w/o intersections
Q Intersection (& roundabouts)
K Pedestrian crossings and other high risks
R Roundabout
G1 Slope 5-10%, longer than 160 feet
G2 Slope >10% longer than 160 feet
S1 Curve radius < 1600 feet - divided roads
S2 Curve radius < 1600 feet - two lane roads
Road classification definitionsInvestigatory level (31 mph)
Investigatory Levels (US)