Last week’s article was a call from experts and six U.S. senators for the National Highway Traffic Safety administration to exert more oversight in vehicle automation. Here’s why.

In a study of driver behavior by the Insurance Institute for Highway Safety and the Massachusetts Institute of Technology’s AgeLab, drivers were more likely to check their phones, eat a sandwich or do other visual-manual activities while Volvo’s “Pilot Assist” partial automation system was active than when driving unassisted.

Another IIHS-AgeLab study found drivers using Tesla’s “Autopilot” system quickly mastered the timing interval of its attention reminder feature so they could prevent warnings from escalating to more serious interventions. Some used this skill to continue engaging in distracting behaviors, punctuated by quick moves to stop the alerts.

In both these studies, drivers adapted their behavior to engage in distracting activities, according to IIHS President David Harkey. “This demonstrates why partial automation systems need more robust safeguards to prevent misuse.”

Using cameras and other sensors, partial automation systems can keep your car moving down the road in the center of the lane at the speed you select, slowing down to avoid other vehicles and then accelerating again when the way is clear. However, drivers are supposed to pay close attention to what’s happening on the road and be ready to take over at any time. As the new studies show, not all drivers do.

One of the studies examined how likely drivers were to engage in non-driving activities when using the automation on highways relative to driving unassisted. The study then evaluated how this relationship changed over time.

Drivers in the study were more likely to be distracted while driving with Volvo’s “Pilot Assist” two weeks after they had the vehicle than in the first two weeks. This suggests they became bolder or more complacent as they got used to the system.

Vehicles with partial automation have features that recognize forms of driver distraction and appropriately, have warnings to alert drivers to reengage in the task of driving. The drivers could indicate they were still engaged by making a slight steering adjustment, tapping the turn-signal stalk or toggling a dial on the steering wheel.

If the system didn’t detect one of those responses soon enough, it would begin a series of escalating visual and audible alarms and alerts. As a last resort, Tesla’s “Autopilot” would slow the vehicle to a stop, deactivate, and deny the driver access to the feature for the rest of the trip.

The researchers found that drivers performed non-driving secondary activities, looked away from the road, and had both hands off the wheel more often during the alerts and in the 10 seconds before and after. This suggests that drivers learned how the attention reminders worked.

According to IIHS Senior Research Scientist Alexandra Mueller, the study’s lead author, “These results show that escalating, multimodal attention reminders are very effective in getting drivers to change their behavior.”

However, she cautioned that better safeguards are needed to ensure that the behavior change translates to more attentive driving.”