Brick duplo compatible elevation piece that can be used to make spirals (with the curved tracks) or just straight bridges (with straight tracks). Each piece increases the height by exactly one duplo brick height per track, so it's easy to build the supporting towers. 12 pieces makes a full circle, which becomes very stable. 

I used generic PLA. Anything should work, but recommend doing a test print with one first to make sure the standard bricks clutch well, otherwise may need to tune printer settings to fix.

Each piece is only 14g of filament!

Once a full loop is completed subsequent loops can be stacked on top of the first loop with 12 brick heights delta. Since the connector is half a brick height on the column side this means you need 11.5 in height between layers:

To help with getting the right height I have another model for a 2x2 half-height brick:

And models for pillars:

Update see also new double-side version for better stability: