That depends how the UI to the extra power is implemented. I bet the lower power mode still has increasing power the further the pedal is pressed (as opposed to

That depends how the UI to the extra power is implemented. I bet the lower power mode still has increasing power the further the pedal is pressed (as opposed to simply finding there is no extra power if you floor it -- a smooth monotonic graph rather than one clipped at the top), so you still have a feedback loop going through the latency of conscious thought as you press the pedal the "right" amount to accelerate (not flooring it), find that it's insufficient, and now still have to choose between braking and accelerating -- either braking after you've already decided that's the less safe option and accelerated enough that that's probably more true than it was previously, or accelerating now that you've wasted some time and need to accelerate more briskly than you previously would have (maybe even flooring it, which as you say is not a safe place to be) while also having doubts about whether attempting to accelerate faster will actually suffice since your current pedal input should have also sufficed. Edit: Not to mention, lack of safety in an absolute sense doesn't mean that the safest option for a given driver (predicated on the assumption that it looked safe to go as far as the onramp and there's no way off other than merging eventually) wouldn't be to floor it to merge. In the Bay Area in particular, drivers are notoriously aggressive about both tailgating and blocking merge attempts, and faced with a tricky merge you might find that braking input is unlikely to work (no openings toward the rear), heavy braking to avoid the situation is unlikely to work (in theory you're supposed to yield to the freeway traffic, but doing so will probably result in the tailgater behind you rear-ending you), and the nearest available opening in front of you requires heavy acceleration. It'd be better if everyone could be polite and zipper merge, but in a bad situation with limited personal control you can only hope to make the best of it.