The left edge appears to be uneven. The rails are attached to an I beam or channel. It's hard to tell who wide each course is but it appears to be about eight or ten feet. That's a real narrow cattle guard, so there is a reason for it being wider, maybe a sharp turn on a narrow road.
Typical cattle guards in the oilfield were twelve feet minimum. Most were larger, often 16-18 feet until the rig was moved and the frac trucks were done. Sometimes we changed out cattle guards to more narrow after the well was completed.
Who ever built this one had not done a lot of them. Splicing is frowned on since it tears up tires. The CCC installed a lot of rail cattle guards. This does not appear to be one of those.