A: The following is from our book McHenry Accident Reconstruction in the section Vehicle Control Factors: (a list of references is also below)
Hydroplaning OR Hydrodynamic Drag?
Dynamic hydroplaning occurs when the amount of water encountered on the roadway by a rotating tire exceeds the combined drainage capacity of the tread pattern of the tire and the texture of the pavement. The mass and viscosity of the water cause it to resist being displaced from between the tire and the pavement, thus generating lift forces on the tire which reduce tire contact with the pavement. When the lift forces are sufficient to completely support the load on the tire, contact with the road is no longer made and full dynamic hydroplaning is said to occur.
Prior to the onset of full tire hydroplaning, a transitional condition occurs in which the surface contact area of the tire footprint is decreased as the vehicle speed is increased. This condition is sometimes referred to as “partial hydroplaning” and it is associated with a reduction in the effective friction coefficient. The capacity of the tire tread grooves for water flow is an important factor in limiting the development of partial hydroplaning. Thus, at a given operating condition on wet pavement, the effective friction coefficient is reduced by worn tires.
The following physical factors are involved in the occurrence of hydroplaning of automobile tires:
- • Tire construction type, size and aspect ratio
• Tire loading
• Tread depth
• Tread pattern
• Inflation pressure
• Pavement surface texture
• Water depth
• Length of path in standing water
• Vehicle speed
Figure 1 Hydroplaning Speeds vs. Small Water Film Thickness, from ref  Figure 2 Susceptibility of some ground vehicle to hydroplaning (From Ref. ) Figure 3 Curves of the coefficient of friction for different velocities and water depths, Tire 5.60-15, Load 551 Lbs, Tread 100%, P=22 PSIG (Note: 0.5 mm=0.02 in, 1.0 mm=0.038 in) (Ref. ) Figure 4 Effect of tread pattern groove depth on braking grip, “flooded” road conditions (Ref. [2) REFERENCES:
- 1 Huebner, R.S., Reed, J.R., Henry, J.J., “Criteria for Predicting Hydroplaning Potential”, Journal of Transportation Engineering, Volume 112, No. 5, Sept. 1986.
2 Clark, S. K., editor, Mechanics of Pneumatic Tires, U.S. Dept. of Transportation, NHTSA, 1981
3 Ivey, D.L., Mounce, J.M., “Water Accumulations”, Chapter 6 of The Influence of Roadway Surface Discontinuities on Safety, Transportation Research Board, National Research Council, Washington, D.C., 1984.
4 Navin, F., “Hydroplaning and Accident Reconstruction”, SAE Paper No. 950138.
5 Hight, P.V., Wheeler, J.B., Reust, T.J., “The Effects of Right Side Water Drag on Vehicle Dynamics and Accident Causation”, SAE Paper No. 900105