The cars on our roads are, on average, getting older. This is thanks, in part, to more reliable parts, better maintenance, and also slightly more depressing causes like lengthier auto loan terms. But just because the cars are lasting longer mechanically doesn’t mean the interiors can keep up, and this is a new problem for automakers to solve.

A recent research study by IHS Markit suggests the average age of cars on the road is at an all-time high, which is good because it means we’re getting more life out of the resources that went into making those cars, but bad because people aren’t necessarily holding onto their cars for that reason, from :

The average age of cars and light trucks on U.S. roads reached an all-time high of 11.8 years in 2018, according to research firm IHS Markit. That’s partly due to improvements in reliability – engines are lasting longer as components become more resilient. It’s also because of lengthier loan terms, which incentivize owners to keep their vehicles longer as they pay off the debt.

And the average age of cars on the road is only expected to climb in the next four years, according to the same research firm:

By 2023, there will be about 84 million vehicles on the road that are at least 16 years old, reflecting a 240% increase from 35 million in 2002, according to IHS.

And that poses a significant challenge.

The challenge is that not all of the parts of modern cars are necessarily designed with 16 years of daily use in mind. While keeping a car maintained, or paying for consistent necessary repairs over the lifetime of the car may keep it running, it’s less likely that people are treating the car’s interior with the same amount of care and detailing.

That means the part of the car we interact with the most, the interior, likely isn’t in as good of shape as the mechanical bits after 10 years on the road, and thus could ultimately start to hurt automakers’ brand image of quality materials and reliability, even if the car still drives.

Some suppliers are now working on a solution to this problem, again from USA Today:

At auto supplier PPG, which makes paints and coatings, engineers are recalibrating their approach to help automakers develop interiors that hold up for 15 years instead of 10. That means paying more attention to coatings used for armrests and seat fabrics, for example.

But boosting the longevity of interior parts by 50% requires an investment in new material composition and design, said Rebecca Liebert, senior vice president of automotive coatings and mobility for PPG.

The article also points out that ride-sharing services are also changing up interior reliability, as the car is getting far more use shepherding drunk people around dozens of times a night instead of just sitting in a family’s driveway most of its life.

A lot of this comes down to engineering materials we’re already familiar with to be more durable without feeling like a coffin of cheap and brittle plastic:

Two of the most commonly cited problems with the interior are material scuffing and seat fabric soiling, according to J.D. Power, which tracks more than 233 specific vehicle problems.

One of the biggest areas for improvement is in what Gruber called “blue-dye transfer,” which is what happens when jeans rub off on lighter seats after heavy usage.

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The good news is that advancements in interior design have led to a 45% reduction in the “problem rate” for seat scuffing and soiling from 2013 to 2019, according to J.D. Power.

That’s in part due to the shift toward synthetic leather. “Leather is a little more resistant to scuff and soils than cloth materials would be,” Gruber said. “Our research has shown that consumers don’t even know that it’s not leather.”

Along with synthetic leather, the article also describes disguising harder, more durable plastics as other materials, like plastic panels mimicking open-grained wood. If the materials seem less unnatural, maybe they can get away with not being as soft to the touch but consequentially fragile as the materials we’re currently spoiled with.

Wood is seen as a nice interior treatment, and everyone knows wood is supposed to be hard. You’re just making the hard brittle plastic copy something that is also hard and brittle, but making it seem luxurious.

As , the key to longevity, and somewhat also reliability, is maintenance. Famously “unreliable” enthusiast cars are still around today because they’ve been cared for due to their status.

Perhaps part of the solution here shouldn’t just be making more durable materials, but also just making cars that people can care more about, and making more of an effort to get them to care about the cars, than just solely selling them off as reliable, hassle-free, efficient transportation appliances?