telling the app something like, “Send a message to Mary: I’m going to be late for dinner.” Vlingo works in much the same way.
Yager’s study is thought to be the first to evaluate the safety of voice-to-text apps as an alternative to fully manual texting.
In the study, 43 drivers navigated a 3.8 mile course along the runways of a former Air Force base that now serves as Texas A&M’s Riverside campus. They were driving a 2009 Ford Explorer equipped to record the drivers’ response times, gaze direction, speed, and lane position.
Yager and her team studied four scenarios: a baseline 30-mph drive with no texting, a drive that included manual texting tasks, a drive using Siri on an iPhone 4S, and a drive using Vlingo on an Android phone. A green LED light was mounted on the Explorer’s dashboard, and drivers were instructed to press a button every time they saw it come on. Their response times served as a measure of their distraction levels.
For the voice-to-text tasks, drivers were using the phones just as they would if they’d been standing on the sidewalk: that is, by holding the smartphone in one hand, activating Siri or Vlingo with a manual button press, speaking a message, proofreading it visually, correcting it if necessary, and sending it with another button press.
It would have been reasonable to expect to find slower response times among the people who were sending texts the old-fashioned way. And in fact, that’s what Yager’s team found—-their responses were delayed by a factor of 1.92.
The more surprising finding was that using Siri and Vlingo didn’t improve the situation much. “When texting using Siri, response times were delayed by a factor of 1.87; and when texting with Vlingo, response times were delayed by a factor of 1.77,” Yager’s report states.
Drivers also tended to slow down when they were texting, and to spend less time watching the forward roadway. The effects were equally severe whether the drivers were texting manually or using the voice-to-text apps.
In the end, Yager concluded that the voice-to-text apps are no less impairing to drivers than manual-entry texting.
And that’s where Cheyer’s objection begins. It’s already well known that reading small text and manipulating virtual buttons on a screen “decreases attention on the road and increases driver distraction-related incidents,” Cheyer says. That’s why 10 states have banned handheld use of mobile phones while driving.
But in eyes-free mode, visual and manual tasks are reduced to a minimum. “The study seems to have misunderstood how Siri was designed to be used,” Cheyer says.
In regular mode—the way Yager’s subjects were using the iPhone—Siri shows a text message on screen for proofreading and confirmation. But when used with a microphone—either on a Bluetooth headset or on the earbud cord that comes with the iPhone—Siri reads back the message using text-to-speech technology.
In car mode, Cheyer says, “Siri is even stricter and will not execute certain commands that would require looking at a screen.” Vlingo also has a hands-free mode in which all text messages and prompts are read aloud using text-to-speech.
It’s possible that this kind of hands-free, eyes-free texting still causes some level of distraction—but that’s not what the TTI study tested, and to find out, more research would have to be done, Cheyer says.
The TTI study shows only that “non-eyes-free voice input is not a significant win over non-eyes-free manual texting,” he says. “This is the message that should be transmitted to people.”
Perhaps the biggest point in defense of Yager’s study design is that it was realistic. Most people who text while driving—whether or not they use a voice-to-text app—are probably holding and looking at their phones while they do it.
But Yager says her team is definitely interested in studying how voice-to-text applications involving a Bluetooth speaker or headset might affect driver behavior. “Understanding the distracted driving issue is an evolving process, and this study is but one step in that process,” she says.
