Thought I'd kick start this community with a question.

For me (Madison WI) we have some pretty good signal engineering, at least for North American standards. Signal cycles are getting shorter and shorter, leading pedestrian intervals are pretty much standard for every intersection Traffic Engineering touches, and no turn on red and protected left turns are getting added more and more. We're also adding (good) transit signal priority with BRT. TE also recognizes that smaller intersections (fewer lanes) can lead to better intersection efficiency due to shorter cycle times, which is great.

Lately one of the problems is we're limited by the software the traffic signal vendor computers have. For example, shortening read clearance times remains a challenge (https://www.youtube.com/watch?v=7KPGVP85WpU) because red clearance intervals are a fixed time in the signal vendor software and not table-based. :(