Let's make some assumptions about the tracks. Let's say they are straight lines that run parallel to one another. I make that extra assumption because if the tracks ate curved then the steepness will change over time so the question as it is doesn't make sense.

Now imagine you're looking at the tracks from the side. From that perspective they appear to start at the same point (in view of the assumption you made). However, even though they end at the same height, seen from the side, the endpoints won't necessarily align. You can represent the whole situation as the triangle defined by the starting point and the two (possibly distinct) endpoints. The tracks will be represented by the sides that meet at the starting point. Now, if you're measuring angles with respect to the ground you'll notice that the shorter track is necessarily steeper.