Okay, again, I agree this is not in the slightest practical, but also, again, a train accelerating is not vertical g, horizontal g tolerance is much, much higher than vertical g tolerance, especially "eyeballs in" and it increases greatly the less time it is for. Some early experiments showed untrained people could handle around 20g for less than 10 seconds. Also blunt force risks could be mediated almost completely by ramping the acceleration slowly, first reminding people to brace, then gently forcing them back in their seats. Again, ludicrous, nothing designed for comfort of human passengers is ever going to be designed to accelerate anywhere near that quickly and it's completely unnecessary anyways.