Bridges on a competitive Trail Course

Hello -
I have just entered my mare in a very casual Trail Class and am hoping to make a wooden bridge this weekend to start practicing.
Does anyone have any pictures, specs or how to info on a basic wooden bridge with 2x4’s. I would love to find pictures of an arched bridge if possible.
thank you

http://myoutdoorplans.com/bridge/garden-bridge-plans/

http://www.freewoodworkingplan.com/index.php?cat=420

This is perfect. Thank you very much.

Be sure whatever you build is sturdy enough to support your horse safely. You do not want your horse breaking thru or the bridge crumbling underneath you.

we used standard four foot by four foot shipping pallets with two layers of 5/8 inch plywood; four pallets, four sheets of plywood produced a 4 foot wide 16 foot long training aid… that the rabbits loved to build nests under.

The idea was to get the guys onto a surface that sounded differently