"Island" on former PRR Main (NE Corridor)

[Mark5]

I've been riding commuter trains on this for years and the purpose of this "island" between the main lines (near Bowie State) still baffles me:

http://maps.google.com/maps?f=q&hl=en&q=Bowie,+Prince+George's,+Maryland,+United+States&sll=37.0625,-95.677068&sspn=0.010941,0.020084&layer=t&ie=UTF8&cd=1&ll=39.047452,-76.740446&spn=0.010649,0.020084&t=k&z=16&iwloc=addr&om=1

Any theories?

[asciibaron]

curvature reduction in the 1970's to increase train speeds.  notice that MARC uses the #1 track around the outside. Amtrak does not use the #1 track between New Carrollton and BWI until the crossovers at Grove (under MD 32).

-Steve

[Mark5]

thanks Steve! one less mystery.