I was walking to the office and I heard a rumbling noise up the street and burning rubber. It was a MCI D4500 commuter bus like the ones used in NY/NJ and it had a flat. The tires were all-steel Goodyear transit-spec ones. From what I've read and seen about these MCIs, the rear axle is a steerable tag axle and can be "unloaded". The flat happened on the tag axle. In case a drive axle or a tag/tandem axle tire on a big rig or bus fails, can the driver proceed to safety, or it depends on loading and other factors? Is that also why retreads aren't allowed on the steer axle of a passenger bus as a margin of safety?