Did a pretty simple edit using TinkerCAD extend the bottom of the upward slope. The original bridge had a gradual overhang that required 5 rows of overhang starting on the second layer. I've extended down the initial part of the ramp to get past that impossible overhang and now the bridge can be printed upright. 

Printed mine with 3D Best Q 30% wood fill filament with a 0.4mm nozzle and 0.2mm layers. I used supports under the arches but I suspect you could get away without them.