I was just watching today's RTC meeting. The new plan seems to be to lift all environmental speed limits, as opposed to approving specific speed limit increases. Obviously, due to increases in development and traffic during the past 13 years, not all speed limits that were cut will be increased. They want to start with restoring the limits in place before, and then study possible increases to 75. This reduces the problem caused by strict enforcement inducing artificially low speeds, since strict enforcement may prevent 85th percentile speeds 10 mph above the speed limit even if the speed were safe.
They still have to estimate the emissions reductions from the operational improvements paid for with the $54 million and show that the reductions will offset the increase caused by higher speed limits. The projected emissions increase is fairly small, about 0.4 tons of oxides of nitrogen per day. While the EPA has approved the change in the method of implementation (you can raise your speed limit if you offset the emissions increase), TCEQ approval is needed before the environmental speed limits can be officially removed (you must show that these specific improvements will at least offset the emissions increases due to the speed limit increase).
Due to the removal of all environmental speed limits, there may be increases on non-freeway facilities and non-fringe area facilities, unlike what had been proposed before. While no specific speed limit changes were discussed, it is assumed that the environmental speed limits in place will be removed, resulting in increases of 5 mph, where that's safe to do. The changes to 75 may be staged in two steps, and the changes will take time since TCEQ has not yet given approval.