What do you mean goes nowhere? It never got anywhere! (LOL!)
I would have thought an Electrical and Electronic Engineer could have envisaged the many signals that exist and that it is simply a matter of determining which it is and interfacing appropriately. (Then again, after seeing 3rd year Electrical & Electronic Engineering students that couldn't connect a DMM, or text-book authors that still thought electricity had a "direction" (ie, EITHER positive ions/holes OR electrons!) and thought of Maxwell's Equation(s) as something fantastic, I'm not surprised.)
Maybe kirupa wants to design a universal interface? But in that case, I have already provided the info kirupa requires (for most systems).
Maybe when kirupa provides appropriate info, we can progress.
(Maybe kirupa will find his ECUs do NOT provide speed information. After all, why would they?
I don't mind going nowhere - that's like many dreams.
It's going in circles, costing a fortune, trial&erroring that which is already known... (Especially since finding the true & correct info is so easy.... LOL - that's a joke - no chance of that these days! Progress? - yes, if you understand for what.)