What they need to do is more like a clinical trial for a drug.

    Step 0) measure on a dyno
    Step 1) measure on small closed course with a handful of drivers
         who are unknown to the car companies
    Step 2) measure on a larger group of cars in the real world

If these "costs" are unacceptable, then auto manufacturers shouldn't be putting cars on the road. I always thought trusting the ECU to tell the truth was ridiculous, mostly because over end user tampering not the original code. But the effect is the same.

It really is bullshit that so much time has been spent overfitting to the test when real universe exists right here. No model required.

It makes technically no sense if you can harmonize the regular driving condition into one single realistic cycle. Then the results are reproducible and comparable.

OEMs all have their in-house driving cycle to better reflect the reality[1] than the boring standard cycles.

The emission/consumption performance for some given customers is easily predictable.

To prevent cheating, you'll just have to open source the software inside.

[1] Lino Guzzella, Antonio Sciarretta: Vehicle Propulsion Systems: Introduction to Modeling and Optimization (page 22) https://books.google.de/books?id=aVNEAAAAQBAJ&pg=PA22&lpg=PA...

My assertion is that you can't do that with a single realistic cycle precisely because there is a single one. Overfitting will occur, an ensemble of actors can't be gamed.