Triang buildings and trackside accessories are generally 1/32. Some, such as bridges can look OK next to a HO track.
For proper HO scale, use railway scenery, or search for Faller. They make plenty of HO pieces.
Look up Triang Minic Motorways on Fleabay.
They made lovely pit buildings with a press box on top, a Le-Mans style footbridge & a stop/start timekeepers style building.They also sold fencing & flagpoles.Also look out for their pit lane figures. Quite rare, but not as expensive as they ought to be.
All can still be had at a very reasonable price.
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