That scooter that MostlyBonkers was thinking of was the Vectrix (check out the Vectrix forum, below). I test rode one during the late 1990s at the San Rafael, CA, BMW shop. That two-way throttle was one of its best features, plus it also had a slow reverse. The throttle had a neutral position. As I recall if it was stopped, moving the throttle forward past the neutral position, would slowly move the scooter backward, but if the scooter was moving forward, moving the throttle forward would activate the regen feature. I have no idea why that throttle idea was never used again. Probably because whomever still owns the Vectrix brand still owns their patents. 
The scooter was really ahead of the time, although it was a bit too expensive for the market back then and they started selling the scooter through exclusive Italian-brand auto dealers (perhaps because of its high price), which is never a good idea for scooter or motorcycle sales. By the time motorcycle shops started trying to sell the brand, it was already too late as the factory's finances were rapidly sliding downhill. Apparently, they just invested too much in design and development and could not generate enough sales and profit to pay back their development costs. The Vectrix brand tried coming back once or twice over the years, but that never worked out and I have no idea where things stand right now with the brand's intellectual property and particularly its neat throttle design.
Very interesting, thanks Richard.
I think I've found the patent:
https://patents.google.com/patent/US6724165B2/enIt expires in a coupe of years. Take note Zero!
In March of this year it was assigned to GP Technology & Innovation Ltd. It might be a company name change or a different company altogether.
What I don't know is whether patents can be renewed or extended.
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Topic: ZF14.4 - True Range with 2014DS (Read 3422 times)