In the Sunday O, Jim Mayer has an article about the TriMet bus lines that are most consistently late (TriMet defines this as more than 5 minutes behind schedule).
The champion is the #95 I-5 Tigard Express. In fact, all of the worst performing lines are long-haul lines, often expresses, that are most likely to get caught in traffic congestion.
This seems like a very strong argument for the dedicated right-of-way for MAX (presumably Bus-Rapid-Transit with dedicated right of way would enjoy the same benefit). The article offers no solutions, TriMet works to fine-tune schedules to reduce variation, but it’s not a game you can win.
I think the better strategy is to put more real-time information in the hands of riders, exactly what we’re trying to do with Transit Surfer. Stop having riders rely on schedules, and let them know when the bus is really coming!