Splash and Spray Assessment Tool project goals and available resources

Historical overview Definitions and factors that affect pavement

splash and spray Techniques used to measure splash and spray Overview of the Slash and Spray Assessment

Tool project Evaluation of splash and spray for different

pavement surface types and road geometries Related ongoing projects

Lijie Tang, Samer Katicha and Edgar de Leon, Center for Sustainable Transportation Infrastructure

Helen Viner, Alan Dunford, Kamal Nesnas, Fiona Coyle and Peter Sanders, TRL Ltd.

Ronal Gibbons and Brian Williams, Center for Infrastructure-based Safety Systems

David Hargreaves and Tony Parry, Nottingham Transportation Engineering Center

Kevin McGhee, Virginia Transportation Research Council

Roger M. Larson and Kelly Smith, Applied Pavement Technology, Inc.

Mark Swanlund, FHWA Office of Pavement Technology

To develop an assessment tool to characterize the propensity of highway sections to generate splash and spray during rainfall and the impact of splash and spray on road users

Evaluation of prior work in the area of splash and spray mechanisms

Development of a model to predict water film thickness and splash and spray occurrence on pavement surfaces

Evaluation of the impact of splash and spray on roadway users

Validation and refinement of the developed model

Documentation of the development efforts and preparation of technology transfer materials

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1. Splash and Spray Assessment Tool Development Program Final Report

2. TechBrief: Assessing Pavement Surface Splash and Spray Impact on Road Users, FHWA-HRT-15-062

www.fhwa.dot.gov/pavement/pub_details.cfm?id=964

3. Splash and

Spray Assessment Tool

Reduction of Adverse Aerodynamic Effects of Large Trucks ◦ Chapter VI. Splash and Spray Tests

and Results Weir et al. (1978)

Heavy Truck Splash and Spray Testing: Phase II ◦ Used laser to

measure Light Attenuation

Koppa et al. (1985)

Development of a Recommended Practice for Heavy Truck Splash and Spray Evaluation ◦ Compared contrast change

vs laser measurements Koppa et al. (1990)

Splash and Spray Surface Characteristics of Roadways: International Research and Technologies, Edited by Meyer, W.E. and Reichert, J., ASTM STP 1031. 528-541 ◦ Summarized some

previous work Pilkington (1990) [2] Kirsch, J. W., "Informal

Comments on the Road Spray Problem," Document No. SSS-IR-72-1352, Systems, Science and Software, La Jolla, CA, Oct. 1972.

U.K. ◦ Chatfield, A. G., Reynolds, A. K., & Foot, D. J. (1979),

Water Spray from Heavy Goods Vehicles: An Assessment of Some Vehicle Modifications, Department of Transport, London, England

Sweden ◦ Sandberg, U., (1978) Spray Protectors; Testing of

Efficiency, Report No. 171A, Swedish National Road and Transport Research Institute, Linkoping, Sweden

◦ Sandberg, U., (1980) Efficiency of Spray Protectors--Tests 1979, Report No. 199A, Swedish National Road and Transport Research Institute, Linkoping, Sweden

Definitions and Influential Factors

Splash & Spray Splash: “the mechanical action of a vehicle’s tire

forcing water out of its path. Splash is generally defined as water drops greater than 1.0 mm (0.04 inches) in diameter, which follow a ballistic path away from the tire.”

Spray: being formed “when water droplets, generally less than 0.5 mm (0.02 inches) in diameter and suspended in the air, are formed after water has impacted a smooth surface and been atomized.”

Splash & Spray (cont.)

Bow Wave

Capillary Adhesion

Side Wave

Tread Pickup

Weir, D. H., Strange, J. F., & Heffley, R. K. (1978). Reduction of Adverse Aerodynamic Effects of Large Trucks - FHWA-RD-79-84. Washington, D.C.: FHWA.

Factors influencing Splash and Spray

1. Water Film Thickness Geometry Pavement width Longitudinal slope Cross slope

Pavement Texture

(Manning’s Coefficient) Porosity

Rain intensity

Measurement Contact

Non-contact Coiret (2005)

Vaisala Condition Patrol DSP310

Three-zone contact concept (Smith, 2008)

Factors influencing Splash and Spray (cont.)

2. Vehicle Speed

Tire Properties Type, tread pattern,

condition (tread depth), etc.

Tire/Road Interaction

Vehicle Loading and Aerodynamics

Spray Suppression Devices Mud flaps Side-skirts/valance Fenders

(McCallen et al., 2005)

Techniques used to measure splash and spray

Measurement of Splash and Spray 1. Collection

Used in early studies: Maycock (1966) Ritter (1974) Pilkington (1990)

Diagram. Spray collector (Ritter, 1974)

Measurement of Splash and Spray (cont.)

2. Optical Methods

Contrast Change

Light Attenuation

Subjective Observation

Occlusion

(Chatfield et al., 1979)

32 km/h

80 km/h

Example of Optical Methods SAE Standard J2245_201105

Digitizing Method

Laser Method

Occlusion Factor

Ratio of the mean luminance of the black squares to the mean luminance of the white squares

Vehicle-Mounted Systems (experimental)

Pérez-Jiménez, F., Martínez, A. Sánchez-Domínguez, F., & Ramos-García, J. A., (2011), “System for Measuring Splash on Wet Pavements,” Journal of the Transportation Research Board, TRR 2227, 171-179.

VTTI’s Prototype EUROCONSULT Prototype

Project Overview

Literature Review There has been a considerable

amount of research into the problem of splash and spray, but results are often inconclusive and contradictory.

No conclusive link had been demonstrated between water film thickness and splash and spray generation

Main contributory factors to splash and/or spray

Measurement techniques

Model Development

Water Film Model Splash & spray

Model

Exposure Model

Splash & Spray Equations

Splash & Spray Tools

Impact on User

Exposure Model Builds on CalTrans project (Huang et al. 2008) which

updated the California Wet Percentage Time tables. Wet hours (for different thicknesses) Wet exposure = percentage time

2000 Wet Percentage Interpolation Raster Map (%)

Tang, L., Flintsch, G.W., and Viner, H., (2012) “Exposure Model For Predicting Splash and Spray,” Proceedings of the 7th Symposium on Pavement Surface Characteristics (SURF 2012), Sep. 18-21, 2013, Norfolk, VA.

Water Film Thickness 1. Lab Work

2. Generic Formula

3. Calibrated Formula

Material Texture (mm) Stone Mastic Asphalt 0.549 Asphaltic Concrete 0.633

Porous Asphalt 1.644 Tined Concrete 1.011

Smooth Concrete 0.208 Perspex 0.001

zyw SLITkd )( = d = Water depth (m) T= texture (mm) L = drainage length (m) I = rainfall intensity (m/h) S =slope w, x, y, z, w, k = regression coefficients (k incorporates Manning’s coefficient)

33.06.009.04 )(106 −−= SLITxd

Impact on the User (Nuisance) Test under a range of

different controlled conditions

Measure of splash and spray: Occlusion Factor

Correlated with user responses; i.e., subjective ratings of: Obstruction, Concentration Risk Confidence Control

1.Flintsch G.W., Williams, B., Gibbons, R., Viner, H., “Assessment of the Impact of Splash and Spray on Road Users - Controlled Experiment Results,” Journal of the Transportation Research Board, 2012, Vol 2306, pp. 151-160.

Experiments at the Virginia Smart Road

Two following vehicles

Two trucks

Different maneuvers, speed and rain rates

100 Participants Rated obstruction,

concentration, confidence, control and risk

Computed Occlusion

Splash and Spray Model CDF Simulation → Capillary Adhesion + Tread Pickups + Bow wave + Side Wave

→ Combined

→ Used results to build the model

Speed @ 60mph

Speed @ 30mph

Modeled Each Mode Separately Capillary adhesion

Tread pickup

Bow wave

Side wave

CFD for Individual Splash/Spray Mechanisms

Capillary adhesion Tread pick-up

Bow wave Side wave

Model Integration Inputs: Pavement Geometry, Surface Type, Speed,

Location or Rain Intensity, etc.

Outputs: Water density (+ Figure or Map)

Two implementation formats Spreadsheet Matlab program

Quantifying the Amount of Spray

Applied in order

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Capillary Adhesion Tread PickupBow Wave Side Wave

Conclusion I

Produced a model that can be used to predict splash and spray based on pavement surface characteristics and climatic conditions

Potential Improvements The project produced a practical tool for assessing

splash and spray potential based on pavement surface properties and expected precipitation

However, the research team has identified some potential limitations that could be addressed in future improvements of the model: Improvement to the water depth model

(especially for lower level of precipitation) More experiments to verify the most crucial

maneuver Additional field validation experiments

Evaluation of Splash and Spray

Splash and Spray Tools Excel Worksheet

MATLAB Script

Surface Geometry Gradient (%) Cross slope (%)

Pavement width (m) Number of lanes

Rainfall Rainfall rate

Pavement information Type of surface layer Pavement Texture

Water Depth

Driving Conditions Speed Limit

Density of water

Nuisance

Spreadsheet Tool Pavement surface cross slope

Longitudinal grade

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Spray Density

Calculated drainage path

Precipitation

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0.68-inch/h rainfall (10-hour level) non-porous pavement

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1-inch/h rainfall (4-hour level) non-porous pavement

Case Study (cont.)

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Conclusion II Pilot implementation showed:

The developed splash and spray assessment model was practical, and

Can be used to support highway engineers’ decisions regarding highway design and maintenance. Selection of pavement surfaces Develop practical guidance

FHWA

NCHRP

◦ The acceptance testing and demonstration of the Continuous Friction Measurement Equipment [Pavement Friction Management] Impact on Accidents ◦ Porous-Graded Asphalt Impact of permeable surfaces

◦ 15-55 Hydroplaning Improved Water Film Thickness Models

◦ 10-98 Macrotexture Enhance macrotexture characterization (2-D

and possibly 3-D)

Larry Wiser FHWA Office of Infrastructure R&D Turner-Fairbank Highway Research Center 6300 Georgetown Pike McLean, VA 22101 Phone: 202-493-3079 Larry.Wiser@dot.gov

Gerardo Flintsch, PhD, PE Director, Center for Sustainable Transportation Infrastructure, VTTI Professor, The Charles E. Via, Jr. Department of Civil & Environmental Engineering Phone: (540) 231-9748 (540) 231-1569 flintsch@vt.edu