Railway bridge

On the return leg of the evening stroll I stopped, just before we walked under the railway, to look at the bridge . It’s not often seen without much traffic which made for an interesting sight. I thought the light caught some patterns in the brickwork that I had never seen before and that’s why I snapped a photo. I can’t tell if they are intentional patterns or a trick of the light. If they are by design then I think it’s quite a lot of effort for a functional bridge.