While wandering down the Hiawatha LRT bike trail to take a peek at the broken Martin Olav Sabo Bridge, I took a look at the light rail tracks. Rails have the weight and the year of manufacture stamped on their sides—Hiawatha tracks appear to be 115 lbs./yd. and were apparently forged in 2001 (at least along that segment).
Oh, and the rails are already rusting up after not even 3 days of disuse (well, it did rain/snow in the interim, which makes a difference. My car's disc brakes oxidize within hours when they get wet).
I tried to take a photo of the stamp with my phone camera, but the resolution just wasn't enough to pull it off. It's also always tricky to get embossed markings to show up correctly. Someday I'll pull out my DSLR and try again.
Anyway, I'm no expert on rail weights, but this is fairly heavy stuff. I think most of the Twin City Rapid Transit streetcar network used 90-lb. rail. According to Wikipedia's article on rail profiles, most of the New York City Subway uses 100-lb. rail. The Hiawatha LRT tracks could support relatively light freight duty, though apparently they wouldn't be enough for busy mainline tracks like what the Northstar runs on. Wikipedia again indicates that weights above 130 lbs./yd. are used on main tracks.
So, I guess my next task will be to figure out what weight the rails actually are along the BNSF. It'd also be amusing to check out the ex-Milwaukee Road/current Minnesota Commercial tracks which run along the east side of Hiawatha Avenue south of Lake Street. I wouldn't be surprised if the Hiawatha "light" rail tracks are heavier than those...