While I agree that something needs to be done to reduce the road toll, I'm pretty sure that both a curfew and power limits of vehicles are nothing more than band-aid approaches. I'm quite often over-taken on the freeway by P platers in Excel's. If we simply reduce the power of the vehicles, it won't stop people from speeding and dying on our roads.
The answer may be a combination of approaches, but most important is much more driver training.