Treehugger has long complained that the big touchscreen displays in new cars are a dangerous distraction and will probably be risky to people outside the cars who walk and cycle. And we are not even talking about the new Tesla games that you can play while driving. Texting or calling while driving has also been a problem and is illegal in many places now, even though the industry continues to blame pedestrians. Then there are people who eat, do makeup, or just look around at everything but the road. It’s no wonder people are getting killed and maimed.

But what is the biggest distraction and who is the most distracted? A new study by Ou Stella Liang and Christopher Yang of Drexel University asks: How are different sources of distraction associated with at-fault crashes among drivers of different ages and gender groups? The researchers crunched data from the Strategic Highway Research Program Naturalistic Driving Study, which tracked 50 million miles of driving in six states using cars equipped with cameras and radars that could monitor in-cabin activities.

The study looked at six groups of drivers across three age groups—teens, adults aged 20-64, and 65+ older drivers—and two sexes: male and female. The researchers note that some distractions are taken seriously, like mobile phone use, and others less so, like talking to passengers, looking around, or checking out in-vehicle information systems (IVIS).

The results were actually surprising. “In-cabin objects” including moving objects in the vehicle, pets, insects, or reaching for objects or the driver dropping objects were by far the biggest source of distraction for all age groups and sexes. This was followed by mobile phones, which for some reason are almost off the scale for older male drivers.

Close behind in distraction were the in-vehicle information systems, particularly among teen males and older women, but did not seem to be a problem for older men. But it should be noted that these data were collected in a study completed in 2016 before the monster screens we are seeing in cars and trucks now started appearing in large numbers. We previously wrote about a more recent study that found all older drivers had significantly more trouble with touchscreens than younger drivers:

External scenes—defined as looking around at pedestrians, animals, previous crashes, or construction—are the next biggest, and the reason this writer’s wife now insists on doing the driving.

The authors conclude that perhaps we are concentrating on the wrong things when we study or worry about distracted driving.

It is pretty hard to do anything about external distractions, other than not giving driver’s licenses to architects like me or other people who are always looking around. In-cabin objects are difficult to deal with. But in-vehicle technologies are an issue that really should be dealt with; this study probably underestimates their significance.

Much of this is a design problem. Look at the interior of the new GMC Denali; ledges and cupholders and room for so much stuff that might fly around. A center display, a digital instrument cluster, and a 16-inch heads up display projecting on the windshield. The only thing that isn’t moving and changing is the topographical map printed on the dashboard.

The dashboard of my first car, a 1965 Volkswagen Beetle, had a speedometer and a new introduction that year, a gas gauge. There was a switch for the wipers and for the lights. That was it. There’s a nice stretchy storage pouch on the side, but nowhere else to put anything—no dashboard, cupholders, or bins.

Given that the study finds that “the highest contributing distraction types in at-fault crashes were In-Cabin Objects, Mobile Device, External Scenes, and In-Vehicle Information Systems (IVIS),” I wonder if this minimalist approach to car design makes a lot of sense. No distractions here.