You would not have the energy required to accelerate even that small amount.
The closer to the speed of light (c) you are moving the more energy is required for additional acceleration.
This increase in required energy is exponential and if you were moving on this hypothetical train at 99.9999999...9% the speed of like that last tiny bit of speed needed to reach c would be equal to more energy than is available in the universe. I hope this was clear.
Like = light. I sounded like a valley girl. sorry.