\text{Given the ratio} \ \frac{2}{15} \ \text{and the speed of the plane} \ 600 \ \text{km/h}
\frac{S_t}{600} = \frac{2}{15}
S_t = 600 \times \frac{2}{15}
S_t = 600 \times \frac{2}{15} = 80 \ \text{km/h}
\text{Therefore, the speed of the train is} \ 80 \ \text{km/h}
\text{Final Answer:} \ 80 \ \text{km/h}