"Steering on Wintry Roads", Input/Output, ME Departments, April 2005

input/output

by Jean Thilmany, Associate Editor

Steering on Wintry Roads

To prevent your car from spinning out of control on an icy roadway, you steer into a skid. But how far and how fast a turn of the wheel is just right?

The question is more than theoretical in areas like the section of western New York just off the Great Lakes. Buffalo, for instance, which sits on Lake Erie, averages more than 90 inches of snowfall every year.

So it's appropriate that a group of mechanical engineers from the University at Buffalo has set out to study winter driving, in the hope that they can develop new technologies to help drivers steer safely through ice and snow.

Many drivers instinctively know that turning the steering wheel toward a skid can help prevent a spinout, but the real trick to stabilizing a car is knowing how much and how fast to turn the wheel and when to turn the wheel back, said Tarunraj Singh, an associate professor of mechanical and aerospace engineering. Road conditions and the car's speed, tires, and weight are important factors when stabilizing a skidding car. It's nearly impossible for drivers to know how to react safely in every situation, given all these variables, Singh, an ASME member, said.

He and a group of fellow researchers are studying winter-weather questions using a virtual reality simulator operated by human subjects.

"The goal is to create tools and strategies that enhance the ability of a driver to cope with inclement conditions," Singh said. "Technology can supplement the natural instincts of drivers, helping them take corrective action and stabilize their cars in worst-case scenarios."

In which direction does one turn the steering wheel during a skid? Researchers are creating technology to help drivers take correct action.

In the university's virtual reality laboratory, drivers at the wheel of the simulator are confronted with various driving conditions such as icy roads, poor visibility, inappropriate speed, and locked brakes that, together or alone, might lead to a spinout. A controller developed by Singh and his team monitors the vehicle's slip angle as well as the driver's reactions to various driving conditions.

As drivers in the simulator were confronted with spinout conditions, they were provided cues to guide their maneuvers and help them stabilize the simulated car.

These cues—in the form of audio tones and blinking lights—instructed the driver on how quickly to turn the wheel and in which direction.

The audio cues were particularly effective in helping drivers stabilize the car, even during the most severe driving conditions, according to Singh. "With the audio cues, every driver we tested was able to stabilize the car with no problem," he said. "The visual cues proved less effective, possibly because the driver was overloaded with other visual cues from the roadway and dashboard."

Mechanical engineers hope to isolate the best winter driving techniques by studying people while they operate a virtual-reality driving simulator.

Based on the results, Singh and his co-researchers are considering the question of whether cars could be equipped with alarms that alert and guide drivers when their car is in danger of spinning out. And the researchers soon will begin testing the effectiveness of tactile cues, such as a vibrating steering wheel, which would tell drivers what direction to turn the wheel to stabilize the car.

"Tactile cues may be more effective than audio cues, and they also may be more acceptable to the driver," Singh explained. "Many drivers would be embarrassed if an alarm sounded while they're driving—especially if they have a passenger with them. The implication would be that they're a bad driver because they put the car in a dangerous situation."

As Singh put it, "It's very important to consider human factors when testing the effectiveness of these technologies."