Large Scale Central

Need Bridge Drawing

I need to build a small single track bridge, about 14-18 inches long. I have a trestle bridge there now but would like one without trestles. I get to much tree dirt caught on the bents.
Does anyone have a simple design or know where I can get one.

I will cut my own wood for the bridge, will be using Mahogany as it weathers nicely and stands up very well the Texas weather.

Thanks