I recently did some curved and straight deck bridges based on setrack spacing, but this design is a double-track version based on Streamline track spacing and with a lattice effect sides.

I have also done a single-track version that can be foundhttps://www.cgtrader.com/3d-print-models/games-toys/other/model-railway-single-track-straight-bridge-deck-lattice-sides

The spacing is about 52mm between the centers of the two tracks. I have designed this so it can be printed in multiple lengths.

I have designed this item so it can be printed on most FDM 3D printers without supports, but I recommend printing with a 0.4mm nozzle.The deck section is approximately 110mm wide and 23mm high, but this comes in various lengths. 62mm, 92mm, 122mm, 150mm, 182mm, 212mm, and 242mm (There is 1mm of extra detail at each end).There are a lot of files with this design but you will only need to download the lengths you require.

I will also look at adding some pillar supports for those who may need them.If you have any questions, please feel free to contact me.

The design has been tested on the Bambu Labs A1 printer with a 0.4mm nozzle. I used ELEGOO PLA+ Filament 1.75mm Grey https://amzn.to/4bU03sx (Affiliate Link)

This item has been designed at OO gauge, 1/76.2 scale.For HO Gauge print at 87%, 1/87 Scale,For O Gauge UK print at 175%, 1/43.5 scale,For O Gauge International print at 158%, 1/48 scale,For TT120 Gauge print at 63.5%, 1/120 scale,For N Gauge UK print at 51.5%, 1/148 Scale, (Caution: I have not test printed this in N gauge scale. will probably need a 0.2mm nozzle to print).

use this link to join CGTrader and download my designs.

https://www.cgtrader.com/designers/PJD1974?referral_id=3218445