For a place called “The Sunshine State,” Florida gets lots of rain.

Florida is the fifth wettest state in the U.S., averaging more than 53 inches of rain each year. All that rain means wet roads, and wet roads can potentially lead to hydroplaning.

If you’ve experienced hydroplaning, you know how scary—and dangerous—it is.

“Imagine yourself driving on a sheet of ice. If you slam on the brakes, you’re basically just going to slip on the ice rather than coming to a stop,” said Hyung Lee, a senior civil engineer with Applied Research Associates, Inc. (ARA), and principal investigator on a project to help reduce hydroplaning in Florida. “The friction is literally zero. You’ve basically lost control of your vehicle completely.”

Hydroplaning is defined as the condition that exists when a film of water or another contaminant is present at the tire-pavement interface and completely separates the tire from the pavement surface, as shown here.

The Florida Department of Transportation (FDOT) designs pavements to resist hydroplaning based on accurate measurements of which types of roads and pavements are most prone to it.

FDOT recently finished a project with ARA that updated its hydroplaning prediction (HP) software – originally developed in a previous project (BDK84-977-14) – to more accurately anticipate the traveling speed at which a vehicle begins to hydroplane on different pavements.

The project improved the tool by adding new features and capabilities after analyzing the near decade of user-experience data collected since the tool was originally deployed in 2012. This tool is fortified with FDOT’s resilient program in response to the impacts of global climate change.

Hydroplane prediction and more

Weather-related crashes are as common as the rainfall events that cause them.

The National Highway Traffic Safety Administration reported that in 2007-2016 there were more than 1.2 million weather-related crashes each year in the U.S. – 70% of them involved wet pavements. For that same period, weather-related crashes resulted in 410,000 injuries and over 5,000 fatalities.

The updated HP tool has the potential to reduce hydroplaning on Florida roads. While the older version of the tool generally outputs a single number representing the hydroplaning speed, the latest version enhances opportunities for analysis. Alongside giving practitioners the ability to calculate the hydroplaning potential continuously along lengths of the roadway, it streamlines the process, organizes the data, and has new features that consider risk.

The thickness of total water flow (y) is defined as the thickness of the water flow measured from the bottom of the pavement texture, whereas the water film thickness (WFT) is the thickness of water measured from the top of pavement texture asperities. The WFT is used for predicting the hydroplaning speed.

“Take pavement macrotexture as an example. Maybe we know a pavement has a hydroplane speed issue based on low macrotexture, but if we can improve our mix designs with higher macrotexture, that hydroplane potential might be reduced,” said Charles Holzschuher, FDOT State Pavement Materials Engineer and project manager for this effort. “That might help the design parameters when facilities are being built – such as added capacity or geometry constraints.”

The tool uses calculations that involve pavement characteristics, roadway geometry and design, temperature, driver and vehicle factors, and rainfall event details.

“We have a tool that is objective based on the data and can provide some comparison for a design,” Holzschuher said. “We can look at different analysis roadway designs and maybe that could help improve safety and reduce the hydroplane potential.”

The future of the HP software will ultimately lie in subsequent data collection, according to Lee. Currently, FDOT is likely the only DOT that uses an HP tool in the design and engineering of state roads. North Carolina DOT and other agencies have shown interest in the tool.

“We want everyone everywhere to be safe on the roads,” Holzschuher said. “We’d be thrilled if this tool helped others outside Florida.”

Further Reading

BE570 2020 Enhanced Hydroplaning Prediction Tool Final Report | Summary