I would like to add that my Garmin has successfully routed us around interstate closures or heavy traffic due to a incident on the highway. You can pretty much trust the routing. Again: the program knows your rig type and dimensions to select the alternate road.
However, Garmin's routing, from what I can tell, may not be as "real time up-to-date" as Waze or Google Maps. For instance, I have had it try to route me around bottlenecks, when, having decided to go on through them, turned out to have cleared. On another occasion, Garmin tried to route me miles way out of the way to an alternate crossing of the Mississippi River. The problem was some road closures due to flooding in eastern Arkansas the night before. Pulling over, I checked the highway department site and determined that they had reopened and the Garmin router had not yet got the word.
This reemphasizes what others have said. Pick your tool, but don't use just one tool. Use your judgement and cross check various sources if in doubt. Going over the route the night before and satellite checking the next scheduled stop are good ideas, too.