Infotainment systems that require only one command from a driver are a better way to keep older motorists focused on the road than multiple step systems, according to recent research from the Insurance Institute for Highway Safety and the Massachusetts Institute of Technology's AgeLab.

A previous IIHS study, released in 2015, concluded that voice command systems create less visual distraction than systems that require visual or manual interaction. That study also concluded that systems requiring a single voice command instead of multiple ones were preferable. The more recent research sought to determine how age might affect these conclusions.

The study observed 80 drivers between the ages of 20 and 66 as they made calls during free-flowing traffic on interstates in the Boston area. Half of the participants drove a 2013 Chevrolet Equinox with a single command MyLink system, while half used a 2013 Volvo XC60 with a multiple command Sensus system.

After they were trained on how to use their infotainment system, each driver was asked to call four different contacts using the buttons and knobs of the system. They were then asked to make four contacts using voice commands.

Researchers used camera footage from inside the vehicles to analyze how often drivers glanced away from the road, how long it took them to make each contact, and errors made when attempting the contact. They also studied vehicle performance data to look at steering wheel movements.

The study confirmed that systems were less distracting when voice commands were used instead of manual interaction. Drivers generally took longer to complete calls, glanced away from the road more often, and made more errors as age increased.

For every 10-year increase in age, drivers took an average of 3.7 seconds longer to make a phone call. The percentage of glances away from the road lasting longer than two seconds also increased by 0.4 points with each of these increments.

In the group testing the single command MyLink system, however, there was no increase in distraction as age increased. Drivers in this group kept their eyes on the road for about 85 percent of the time they were making a call, regardless of age. However, the average length of glances away from the road increased with age with the MyLink system, while they decreased for the multi-step Sensus system.

"Age-related changes in attention, including the demands of using a phone while driving, are well-known," said Ian Reagan, a senior research scientist at IIHS. "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 multi-step voice system or traditional visual-manual interfaces."