The Benefits, Problems, and Functions of Signal Synchronization
Everyone knows that feeling. Waiting at a streetlight for minutes on end, and watching the light turn green for others while your light stays red. Surely there is a way to fix it, right?
It´s a complicated process, but there is one innovation that can alleviate this problem: synchronization. This process is exactly how it sounds. Lights are coordinated along a street so that a driver passes through as many green lights as possible. But how is this achieved?
This process begins with the speed limits. Between street lights, an engineer calculates the time it takes for a person going the speed limit to go from one intersection to another. Then, once they calculate this time, they set the signal timers. For each light, the time which the signal turns green is offset by this amount of time. While this means that not all the lights on a street are going to be green, it means that when a person passes through a green light, the next light they reach is most likely going to be green (assuming they drive the speed limit).
However, this may raise some problems. In bustling cities with hundreds of crowded streets, there are too many intersections to coordinate. This means that streetlights in these cities cannot be perfectly synchronized, and certain streets may have to be favored in terms of synchronization. Typically, cities with the most traffic are prioritized in synchronization, which means longer-than-normal waits for less popular streets. But in some cities, this synchronization can actually be shifted, with coordinators choosing which streets to prioritize at certain parts of the day. Problems may also arise in terms of turn signals. Especially if an intersection includes a large amount of left-turn traffic, streets on the opposite side of this traffic may be favored less in terms of prioritization. Perfect synchronization is nearly impossible, especially in cities with a complex array of intersections. But why do we still do it?
Streetlight synchronization is typically done for environmental benefits. In a world with increasing car usage, concerns of emissions have led to these measures. Waiting at stoplights leads to increased trip times, which leads to increased emissions. And in areas with synchronization efforts, these emissions have been reduced. In Orange County, California, it has been calculated that county-wide synchronization efforts led to a reduction of 52 million gallons of gas consumed, which translates to 885 less pounds of carbon dioxide in the atmosphere. Adding on to this, citizens in Orange County report a higher satisfaction with road usage, with more citizens reporting a better travel experience with less stops.
Signal synchronization is a simple process in principle. But when it is scaled to the size of a city, or even a county, perfect synchronization seems more and more difficult to attain. Despite this challenge, civil engineers should still tackle synchronization head on. With signal synchronization, engineers have the ability to improve the efficiency of a city, increase citizen satisfaction, and reduce the environmental detriments of everyday car usage.
