Canton Viaduct questions

What is the purpose of the extra rail seen in this photo of the Canton Viaduct in Massachussetts? I assume it is intended to keep the trucks more or less in line in the event of a derailment.

http://www.railpictures.net/viewphoto.php?id=77479

Also, what is the speed limit here? An article in Trains magazine claimed that the Acela Express crossed it at 140 mph, but being on a curve, that cannot be the case. (The Acela is limited to 130 max on curves.)

The extra rail in the gauge of the tracks at this location is used to help
prevent a roll over or other possible problem in the unlikely event of a
derailment at this location. They help keep the train upright and within
the gauge of the track. They are generally called a guard rail and are in
common use on bridges especially on main lines.
Speed at this location - High Speed Train Set - 125
Regular equipment generally 120 or 115, could be lower depending on
train consist.
Noel Weaver

Ah, that's what I figured. Thanks for the info!

That's odd--the guardrail on the left (westbound?) track is on the outside of the curve. When only one guardrail us used, it's usually on the inside, to catch the back of the inside-facing wheel after it leaves the running rail (when a train derails on a curve, it almost always points outward; thus the inside-facing wheel lands between the rails). A train derailing on that curve would foul most of the guage before touching the guardrail.

Anyone know why the guardrail was placed that way? Something to do with the superelevation, maybe?

The guardrail in the photo would keep the train away from the edge of the bridge and falling off, it appears. ?

I'll buy that--better to slide across the guage than off the bridge.

i agree with that

The Rail was put in place this past spring and has been installed in 1/4 mile strings. Curve worn rail was replaced between Readville and Mill River, project completed in July