I’ve noticed that on railroad bridges and trestles and also in tunnels there are two rails that branch out in a diamond shape between the two main rails that the train runs on. What are these for? I hope I’ve described them well enough.
Guard rails. In the event of a derailment, they’re to help (not prevent) keep cars close to the rails an hopefully not fall off the bridge (open side) or hit the sides (girder or truss bridges). The points at the end gather the wheels and keep them close to the rails.
The purpose of the “rails” inside the rails is to keep anything that derails from leaving the track proper…the idea is that the extra rails will guide the wheels and trucks along the track, and trap, then steer any wheel that is off the rail, preventing the car from hitting the bridge structure or the tunnel wall.
(see tom’s reply above!)
Most of the time, they work.
Ed
Why have so many of these been removed? They used to be on every bridge but now most of them are gone.
More bridges nowadays are through-deck structures that have ballast beneath the tracks. Less chance of a derailment hitting something vital to the structural integrity of the bridge. That’s just my speculation, until somebody in authority (MC?) tells me differently.
On ballast deck bridges it’s so they can surface the track with track machinery. With the guardrail, everything inside the rails must be tamped by hand. Also the engineering standards decide differently how guardrails are placed, based on height. They are a necessary pain in the behind to deal with. (i.e. - Why dealwith them if the standards say you don’t have to???)
Don’t most railroads have standards regarding this? I seem to recall that guard rails are REQUIRED for bridges over a certain length. Or this ancient history?
Not length, its height (T/R to f/l of ditch, 16 feet on BNSFand position of structural members in relation to the track. The rules on the two western Class 1`'s are considerably relaxed from the old days…
Think of gaurd rails on a RR bridge like the gaurd rails on a highway keeps stuff were it should be instead of all over teh place in the river.
Here in milwaukee on most of the bridges they still have those gaurd rails and. I have always wondered what they were for but now I know thanks for expailing it for me. [:D][:D]
Thanks everybody! At first I did think they might be used to keep trains on the bridge if they derailed, but I didn’t think they would do that much to keep them on. Now that I think about it, it does work.