Voice-command systems help older drivers focus on the road

December 7, 2017

Buy a new vehicle today and chances are good it will have an infotainment system for making phone calls, playing music, and getting directions — all via voice command. The idea is to help drivers access these features while still keeping their eyes on the road.

When it comes to placing phone calls, earlier IIHS research showed that voice-command systems are less visually distracting to drivers than systems requiring visual and or manual interaction, and the best ones need only one voice command, not multiple voice inputs (see "Voice systems can reduce some types of distraction," March 3, 2015). A key question for researchers is, does the benefit of the single, more-detailed voice-command approach extend to drivers of all ages?

A new study by researchers from IIHS and the Massachusetts Institute of Technology's AgeLab indicates that design matters when it comes to how drivers, regardless of age, interact with voice interfaces, and it offers further evidence that voice-command systems don't demand as much attention as visual-manual interfaces. Making hands-free calls using a single-step voice-command system rather than fiddling with buttons or knobs helps older drivers in particular remain attuned to the road. That is an important finding because drivers generally attend to the road less while using infotainment systems as they age.

"Some voice-command systems help drivers focus on the road more than others, but none completely eliminate visual demand or other demands on attention. In this study, we were interested in seeing how the characteristics of different voice interfaces affected drivers across a wide age range," says Ian Reagan, an IIHS senior research scientist and a co-author of three papers based on the experimental study.

Researchers compared the experience of 80 drivers 20 to 66 years old using embedded voice systems from two vehicle makes to place calls while driving in free-flowing traffic on Boston-area interstates, accompanied by a research assistant. Half of the group drove a 2013 Chevrolet Equinox with the MyLink system, and half drove a 2013 Volvo XC60 with the Sensus system. A cellphone programmed with a list of more than 100 contacts was linked via Bluetooth to the infotainment systems.

Each driver was trained in how to use the vehicle system while parked and then had to use Sensus or MyLink to call four contacts using buttons and knobs, and call four contacts using voice commands.

The two systems used different design approaches. Calling a contact using voice commands with Sensus required multiple statements to navigate through different system menus, while the same task required a single detailed voice command with MyLink. The systems' visual-manual interfaces also differed. To call a contact manually, Sensus required the driver to scroll through the contact list using a rotary knob, while, with MyLink, the driver used a rotary knob and push button to access the alphabetical range containing the desired contact and then scroll through that more limited list.

Researchers later used video footage and vehicle performance data to analyze glances to the road ahead, the time required to call each contact, errors when placing calls, and the frequency of steering-wheel movements.

In general, as age increased, drivers took longer to complete phone calls and made more off-road glances lasting longer than two seconds when placing calls relative to younger drivers. For example, for every 10-year increase in age, drivers took 3.7 seconds longer to make phone calls, and the percentage of long glances away from the road increased 0.4 percentage points. Older drivers also made more errors when using the different systems.

However, the single voice-command approach eliminated age-related decreases in attention to the forward road. Drivers of all ages kept their eyes on the road about 85 percent of the time when they were making calls with MyLink's single voice-command system. In comparison, drivers spent less time looking at the road ahead when using the buttons or knobs with either system and Sensus's multiple voice inputs, and the percentages decreased significantly with age. Similarly, the average length of glances to the road ahead increased with age for drivers using MyLink's single voice-command system but decreased with age for drivers using the Sensus multistep voice interface.

"Age-related changes in attention, including the demands of using a phone while driving, are well-known," Reagan says. "This study contributes new information to the field by showing that the single-command voice interface design to some extent controlled the age-related decrements in attention by allowing drivers of all ages to look at the road more when placing phone calls compared with a multistep voice system or traditional visual-manual interfaces."

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