Hand reach measurements are done by three different methods.

First is with an extended index finger. Imagine you pushing a button with your index finger. That's it. Where in the vehicle will this finger touch.

Second is a two finger reach. Really it is whether you can pinch something between your thumb and index finger.

Third is a closed fist. Like when you grip the steering wheel in a completely closed hand.

Here is a very basic diagram of how hand reach is measured.



If you need more information contact SAE for the regulation.

There are programs that can measure pretty much anything. The issue with having a start model that is ergonomically correct is that there are so many ways ways to package a human in a vehicle that those variations do not lead to a "standard model.

For instance, if I simply change the angle of the windshield by 1 degree then the rear view mirror has to adjusted, then the seat back angle may change and the steering wheel angle, then the outside rear view mirrors need adjusting ad nausea.......

Then once everything is moved it has to be re-evaluated.

So starting with an ergonomically correct model is not really an option. Starting with a parametric model and then changing the manikin to fit the package inputs and then measuring all that is necessary is an easier way to go.