MoBikeFed has done a great job of explaining & summarizing the issues. For example the main problem with the mirror requirement is it just isn't feasible. St. Charles County is on one of the major bicycle routes across the country. Are these cross-country riders going to stop and buy a mirror just to get across St. Charles County when no other county or state they've passed through has required it? They won't even know it's required for those few miles. How's it going to be enforced? It's a pointless law.
I'm thrilled that we have a situation where MODoT is on our side. For years MODoT has been "the enemy", blocking every attempt to get Complete Streets on the floor, and opposing any attempts to incorporate cycling & pedestrian use into roads & bridges. Over the past year they've appeared to turn around completely.
2009 Trek 7.2FX WSD, brooks Champion Flyer S, commuter bike