mtrumpet wrote:
Just a curious diagnostic thought...By chance, when your brakes were smoking and you eventually were able pull over to check them, were you able to smell anything? Burning oil/fluid would smell different than hot brake pads which may help to point you in the direction of a possible problem, if there is one.
My thoughts were similar to yours. Generally the smell test will lead you in the right direction. A recent service may have pushed grease from the S cam fitting onto the shoes or a leaky axle seal may be the culprit. The possibility of an automatic slack adjuster over adjusting the one brake may have one wheel over braking also.
Traffic like what the OP was dealing with is difficult to navigate wihtout using your brakes a lot and not getting much cooling time in between heavy uses.