Unusual rail alignment

I was at Science Park waiting for a train to Tufts when I noticed this unusual rail alignment. I first noticed the guard rails which come within two inches of the running rails. I only see these guard rails opposite frogs in switches. What's their purpose here? Then I noticed that the running rails were not placed end-to-end. Rather, the two rails overlap each other by about eighteen inches. The rails running to Lechmere diverge away from the rails coming from North Station. The rails from North Station are tapered.

Curious minds want to know.

In the photograph, I am facing North Station and Lechmere is behind me.

The overlap is an expansion joint to compensate for the expansion and contraction of the bridge.

I don't see the photograph.

A restraining rail may be placed next to the inside rail going around any curve, to catch the flange of the wheel on the inside and therefore prevent the wheel on the ouside rail from trying to climb that rail "due to centrifugal force."

Guard rails between the running rails are often used to help prevent the train from moving too far to one side or the other in the event of a derailment on a bridge or trestle. This in turn helps prevent the train from then striking bridge structure on either side or from toppling sideways .

Disney Guy wrote: ↑Sun Oct 22, 2023 4:28 pm I don't see the photograph.

A restraining rail may be placed next to the inside rail going around any curve, to catch the flange of the wheel on the inside and therefore prevent the wheel on the ouside rail from trying to climb that rail "due to centrifugal force."

Guard rails between the running rails are often used to help prevent the train from moving too far to one side or the other in the event of a derailment on a bridge or trestle. This in turn helps prevent the train from then striking bridge structure on either side or from toppling sideways .

I don't know why the photograph didn't load. These short restraining rails, which I usually see only opposite frogs, were not on a curve.

Those restraining rails are for the expansion joints to prevent a train from "picking" the points.

Those exist to center the wheels over the two rails to minimize the odds of the flanges from picking the joints. The wheels can deviate side to side (or else the wheels wouldn't make it around curves)

Conversely, If you ever ride a commuter train at speed over a switch, you'll feel the train jolt in the opposite direction of the frog. Those rails exist on switches for a similar reason; to pull the wheels away from the point to reduce/minimize the chances of the flange picking the point.