Funny how you thought just the oposite of me. I thought three the same would look boring. And here's a bit of news for you. All three are HO scale bridges. The trestle in the back is a bash of three Campbell trestles. The middle one is two Campbell deck bridges and finally the front one is three Walthers ballasted deck bridges put together. I just used the girders from that kit and applied them to the top of a 1/8" basswod floor. Then I laid the On30 track on top, placed guard rails on the sides and ballasted the track. The wood trestle and deck bridge have hand laid On30 rail on the HO scale ties. Since my trains are heavy, these small bridges needed to be strong, so I tested them with 25 pounds of weight. As you can see, they held up. BTW, my heaviest engine in the 4-6-0 Baldwin. It weighs 12 pounds.
Many moons ago when in college studying architecture, we were challenged to build a bridge that would hold our weight in 1/4" scale, which is the usual scle for drawing architectural plans. I and my partner built a trestle out of O scale lumber using the plans that the HO scale kit provided. We just blew them up. All the joints were glued with carpenter's glue and pinned with straight pins, cut down, to represent bolts. The trestle was flat bottomed, not stepped like the one on this layout. It was 12" tall and 30" long. The test was, of course, to stand on your creation. Most of the entries collapsed under the weight of their builders. Ours did not. I weighed 135 pounds at the time and the darn trestle held me up. What is the point of this story? Just to tell you that the Campbell designs are honestly engineered to be sturdy.
And here is another view.
