‘Adaptive Traffic Lights’ – Enjoy Seeing Red!

by · May 28, 2012

To your left, a mother calls her daughter abroad to wish her a happy birthday. 50 kilometers away, a man just went into retirement to begin the rest of his life. In a galaxy many light years away and after existing for millions of centuries, a star explodes in a magnificent supernova with nothing but dust to commemorate its existence… And yet here you are sitting in your car wondering when the traffic will move another 10 meters.

I have come to realize that being stuck in traffic is a rite of passage for anyone who wants to drive in the city the same way a lion cub is sometimes left to fend for itself so that it can learn how to survive. However, there is nothing wrong in knowing the technological factors that decide whether you wait 50 seconds or 15 minutes in order to get to work.

If you are interested, read on. How do the guardians of road intersections-those red, yellow, and green deciders of our transportation fate- work? In Doha there are two systems of traffic lights that vary according to location; for the sake of convenience, let’s call them Old and Smart.

The Old System: Even though I refer to this as ‘old’, it really means the less automated one. These lights are still centralized and computerized, but they run on older hardware which limits their abilities. The traffic lights utilizing the old system are usually found in the older parts of Doha and are being phased out and replaced with the newer ones. Their concept is simple and if you drive up to such a traffic light at the right time, you will probably be satisfied. They operate on a timed cycle basis. The time that the traffic light stays red/green is preset yet variable; it varies according to the time of day and predicted traffic (usually quite short at night, for example).

The Smart System: These are the more advanced and impressive ones, but they are also the ones you should keep in mind when stuck at major intersections. Their professional name is the Adaptive Traffic Signal System, in that it adapts to the amount of traffic and time of day in order to ease the flow of traffic.

The challenging part will be convincing you how the extra time you might wait is in the end better for you and for everyone else around you. The important thing to understand is that traffic systems are designed with something much more fundamental than simply easing and organizing traffic; their primary purpose is to save energy.

Think about it this way: If five  cars from four sides to a roundabout with a traffic light that made three out of the four groups wait while the light switches from red to green, then those 15 cars would have to come to a complete stop then exert a lot of energy to start moving again, bit by bit. On the other hand, the adaptive traffic light system would understand that there are not many cars on the road and would thus switch very quickly or simply blink amber (meaning that cars are allowed to go if they see the road is clear).

Similarly, if 100 cars from each side were to reach an intersection or roundabout at rush hour for example, an amber blinking intersection will waste vast amounts of energy as cars are constantly ready to move, going at a pace of 10 meters/minute, then a complete halt, then another 10 meters, and so on. Adaptive traffic lights would close all the signals except for one which would remain green until a considerable amount of cars have passed, and then rotate throughout all the traffic lights at that intersection. These traffic lights take into consideration a number of factors, such as car presence on the road (using sensors and traffic cameras), time of day, other lights nearby coordinating traffic, and last but not least, incoming emergency vehicles such as an ambulance or a fire truck.

Tip: If it ever happens that you were driving around, perhaps to take in the beautifully lit Doha skyline, and you end up stopping at a red light that seems to refuse you access while you see the other roads turn green more than once, look out your window to the ground immediately next to you. You’ll see grey/silver looking lines close to the entrance of the intersection.

It looks like this:

Those are sensors, your car should be on top of them in order for them to trigger, after which the traffic system will understand that there is someone on a certain side of the intersection waiting to go through, and you’ll get your turn! But remember, advance too much, the traffic camera might decide to take a quick picture!

Post By Nadim Rifai (5 Posts)

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