Dual gauge

Dual gauge is when there are two different sizes of train tracks next to each other. It's like having a really big lane for big cars and a smaller lane for smaller cars, but for trains!

One size of track is wider than the other. The wider track is used for trains that need to travel long distances because they are bigger and faster. The smaller track is used for trains that travel shorter distances or for trains that are smaller and slower.

Sometimes, both sizes of trains need to use the same track. So, instead of making everyone switch trains or tracks, they just build the two different sizes of tracks side by side. That way, everyone can get where they need to go without any trouble!