I read that the Lexus RX hybrid uses battery power only for acceleration and situations that would otherwise cause a high throttle setting. As a result, it is a simpler system because the car is not intended to run on batteries alone.
The Lexus system allows you to achieve "highway" fuel economy in the city.

Do you know of any other automakers using this approach?

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It (Vienna) is like Paris without the french - David Frost

Now that I think about it, the Lexus hybrid system resembles the KERS system used by Ferrari in the 2009 formula one season. The purpose of the KERS system is also supplementery power instead of primary power.

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It (Vienna) is like Paris without the french - David Frost

I am not familiar with the Lexus system but that is very interesting, I am going to look into it some more and see if any other manufacturers are going the same route.

Thank You WheelBender for sharing that with us.

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Since Toyota is involved in formula 1 racing, it makes sense that the Lexus passenger car hybrid system resembles a KERS system.

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It (Vienna) is like Paris without the french - David Frost