Apparently, 2 of the 3 Skytrain bridges were never designed to also accommodate trains.
https://www.google.ca/maps/place/Marpole+Bridge/@49.1996678,-123.1276435,848m/data=!3m1!1e3!4m6!3m5!1s0x548675f84f6c0721:0xbea3ccce242f45a8!8m2!3d49.1995219!4d-123.1268811!16zL20vMGZqMjYx?hl=en&entry=ttu&g_ep=EgoyMDI2MDYwMy4xIKXMDSoASAFQAw%3D%3D This was allowed to fall apart and catch fire.