This is a new category... reserved for stuff I'd like to see with regards to urban planning and design.
Traffic lights seem to be handled in many municipalities in a haphazard way: rarely is there consistency visually or systemically. I imagine it's because traffic lights are expensive and difficult to install... meaning that an entire retrofit of a city is not likely to happen. Instead, traffic lights are installed/updated when road repairs make such particularly easy or outright necessary — or when an accident happens, and politicos want to mollify a public uninterested in proper traffic calming programs.
But here's my wishlist, all the same:
LEDs — The new, LED traffic lights are superior in every way to all the other implementations I've seen. If you don't know what I'm talking about, you'd recognize the lights because their comprised of a couple hundred smaller bulbs — and look, for all the world, like bugs eyes. They're bright and easy to discern, regardless of environmental conditions. All traffic lights should be of the LED sort.
Directional Beepers — There's a proper word for these, but I don't know it off-hand. These are the aural cues for the visually impaired. All traffic lights should these to indicate when crossing is permitted.
Crosswalk Count-down — You've seen the crossing signals that feature the 25 second count-down timers? Yup... every intersection should feature these.
Automatic Crossing Signals with the CBD — Central business districts are decidedly places where pedestrian traffic is encouraged/expected. All intersections controlled by traffic lights should feature crossing signals that activate without pushing a button ( though buttons are handy placebos ).
Realistic Crossing Time-frames — When a crossing signal is furnished, lights should be timed such that pedestrians can can actually cross all lanes of traffic in the time allotted. If the intersection is large, pedestrian islands should be furnished at the medians, and time-frames should encourage pausing on the island.
Full-stops — Almost every intersection I've come to switches immediately between RED for one direction of traffic and GREEN for another direction of traffic. I would propose that all traffic should come to a complete stop, with all signals being RED for a beat or two when thru-traffic changes directions.
Extended YELLOW — A recent study ( man! I wish I could find it! ) concluded that an extra 1 second ( it may have been less ) of YELLOW before turning RED would decrease light running by 50%. That's an amazing reduction for such a paltry investment of time.
Controlled Mid-block Pedestrian Crossings — Many CBD blocks feature mid-block pedestrian crossings. Unless required for cross traffic ( say, from a parking garage with a mid-block egress ), these pedestrian crossings should NOT have traditional stop lights. Rather, flashing lights ( YELLOW, or better-yet PURPLE, to differentiate these signals from ones where the power is out ), should be installed. When a pedestrian requests a signal, the light turns from flashing YELLOW/PURPLE to flashing RED. This allow safe crossing of pedestrians as-needed, and protects motorists from malicious button-pushing by passers-by.