This suggestion would not give a driver feedback about their driving on their smartphone or computer while is already overwhelmed with information. My suggestion would help a driver to better navigate urban traffic more efficiently, more timely, more safely, improving fuel efficiency and with less idle time at red lights. This system would utilize either traffic sensors, ones already used to change red lights or smartphone location data or both. The idea would give a heads up as to the upcoming change of a light from red to green or green to yellow to red. With the heads up say 1000 feet back from an intersection or ten seconds, the driver can prepare to begin slowing down even before the light turns yellow, or can cost and be ready to continue through an intersection that has a red light. With fuel efficiency at its worst on zero miles per hour startup, this would save fuel alone. Signs signifying a subsequent light are timed to change when a vehicle goes at a moderate acceleration from a first light to the next, the driver can change his or her driving to accommodate this cycle of lights and not need to brake or slow down.
For example, an intersection I come to almost daily is timed and I can see it is green from 2000 feet back. I would typically maintain speed to the intersection. Half the time the light cycles to red before I go through the intersection. With a heads-up showing the light will cycle before I get through it, I could begin coasting and braking if necessary instead of coming to a full stop.
Not all intersections with light signals would need a heads-up like this, maybe a tenth would. The social psychology of a system would cause drivers to adapt his or her driving to learn the cycle of lights, whether or not they are sensor or timed and subsequent lights are in sync with one another.
In my opinion a simple sign placed eight to fifteen seconds at the posted speed before an intersection saying, "upcoming light will cycle, prepare to stop/continue", "next three lights are synced at speed limit", along with publicity would prepare drivers to become accustomed with this early warning. Ultimately an in vehicle or smartphone application could also deliver this early warning from traffic speeds and behaviors, but would be less effective until highly utilized by many drivers.
The benefits besides increased fuel efficiency are numerous. Traffic density, pedestrian traffic and weather conditions could be added to give earlier warning to increase safety with fewer accidents. Frustrated and aggressive driving would be decreased. Quicker commuting would also occur with less from stop accelerating. Less idle time at a red light and waiting for traffic in front of a driver at a newly turned green light would give a feeling of traffic is moving more fluidly as it would be. Less wear on vehicles from lessened braking and from zero acceleration. The benefits can continue with simply informing drivers in more of an advance besides a two or three second yellow light.