Can I use OO figures with OO9 trains?

You can use OO figures with OO9 trains as OO9 is OO narrow-gauge track. It means the track has a width of 9mm rather than a standard OO track which is approximately 16mm but the trains themselves are OO scale which is 4mm to the foot.

These trains appear smaller than a standard OO train but are the same scale.

The bottom line is the track is narrower but everything else is OO scale, so you can use your OO figures.

Narrow gauge trains would have been used in quarries and mines for the movement of raw materials.

Narrow gauge trains were also used during the first world war for transporting troops and equipment to the front lines. Sections of track were pre-fabricated to make the laying much faster under extreme conditions.