4,114 Stoplights in Los Angeles and the Intricate Network that Keeps Traffic Moving is a simple and informative article of some of the advances in moving heavy traffic in congested cities.
I note that the City of Los Angeles has placed major priority on this city function not only by developing their sophisticated control system called ATSAC but also by staffing its operation ... "Yu and his team of 35 engineers and 20 operators."
HONOLULU needs about 1/4 of this level of staffing. It has 1/10.
In general, traffic signal optimization is among the "low hanging fruit" in mitigating some of the traffic congestion in urban areas. But it needs funding and staffing because this is a 24x7 operations with ever changing flows and congestion spots.