For the most part, the Reason Foundation is right; however Feigenbaum leaves out one important fact in the argument. The problem with Feigenbaum's argument--as the Reason Foundation is well aware of--is that Minneapolis, San Diego, and Seattle HOT lanes allow for free non-transponder carpooling. That is, any HOV can get in the toll lanes for free and go without having to pre-register ahead of time or get a toll transponder. That's why traffic flow improved for both the HOT lanes and freeway lanes for these areas as stated in the op-ed. Like LA, Atlanta had a rough start because both of these HOT lanes have ill-advised policies of requiring a toll transponder for toll-free HOV's; non-registered HOV's were displaced from the high occupancy lane, causing traffic to worsen in the regular lanes.
The questions that need to be answered for both LA's and Atlanta's HOT lanes: How many 2+ and 3+ HOV's used the former carpool lanes before the conversion? How many toll-free 2+ or 3+ HOV's are now using the high occupancy lane versus toll-paying non-HOV's? Is there a drop in HOV traffic in the high occupancy lanes?