Traffic lights might be one of the most common things that almost everyone encounters in their day-to-day lives. These systems are essential to maintaining order and safety on roadways. We’ve become so used to these devices that we never pay much thought to them. And today, we will fix that issue.
So, let’s discuss all you need to know about the traffic lights system.
Types of Traffic Signals
Before the advent of cars, roads were mostly occupied by pedestrians and horses. There was no need for traffic signals as there was no traffic to direct. However, once cars came into our midst, we quickly developed these systems to maintain the security and safety of everyone whether pedestrians or drivers.
The traffic system has gone through a lot of big changes, like the old saying goes, “Don’t fix, what ain’t broke”. Still, in modern times, we have developed different types of traffic lights, to ensure maximum safety on the roads.
Vehicle Traffic Signals
These are the most common type of signals that you can observe on the roads. As the name suggests, these are meant to direct the flow of vehicles on the road. These lights come in three primary colors, all meaning different things, and can operate in different patterns of turning on & off.
(A). Red Light (Solid)
The color red has a subconscious effect on our minds, it makes us feel danger. That is why, red lights are often used to signify danger or emergency. In the case of traffic signals, the red light indicated STOP. A solid red light means that vehicles need to come to a stop before the stop line.
(B). Yellow Light (Solid)
These lights are used to indicate caution. A solid yellow light comes when the traffic is about to transition from green to red. A solid yellow light indicates that the signal is about to turn red, so any vehicle that can safely stop before the stop line must do so. And any vehicle that is in the middle of the intersection or cannot slow down safely when the light turns yellow, have the right of way and should cross the intersection. These lights generally operate for 2 to 5 seconds at a time.
(C). Green Light (Solid)
As you may have already guessed, the color green invokes a positive emotion in our subconscious. In traffic regulations, green lights indicate that you have the right of way. However, while entering the intersection immediately after the light turns green, it is advised to do so with caution and slowly and let any vehicle or pedestrian in the intersection the right way.
(D). Flashing Red
Oftentimes, you would’ve noticed a red light flashing like a strobe instead of a solid. This is not a different kind of light hub, but a normal red signal set to strobe mode. You will usually see this signal during the night or near schools/areas with large pedestrian traffic compared to vehicular. This signal means that vehicles are to come to a stop, check for any oncoming traffic or pedestrian, and proceed to cross once the road is clear.
(E). Flashing Yellow
Similar to the flashing red light, these signals are also common during the night time or in pedestrian-dense areas like near a school, hospital, etc. If you see a flashing yellow light, it means to slow down, check for any oncoming vehicle or pedestrian, and continue moving if the road is clear/safe to cross.
(F). Flashing Green
This is not as common as flashing red or yellow lights, and this signal is not similar to its two predecessors. A flashing green light usually occurs before a red or yellow light. This signal denotes that the signal is about to switch from green to yellow or red.
This signal is usually present in traffic light designs that don’t have a yellow light and acts as a proxy for it.
Pedestrian Traffic Signal
Unlike the previous types of light, these lights are used to regulate the movement of pedestrians on the roadways. In most scenarios, this system only uses a single light to indicate whether pedestrians are allowed to move or not. These lights are often connected to vehicle lights, meaning that they coordinate with each other.
How Does a Traffic Light System Work?
A traffic light system consists of a couple of different components that allow for coordinated functioning. These components are – Power Source, Traffic Lights, Control Center/Hub, and Sensors/Detectors.
Every electrical component needs a source of power. In the case of traffic lights, you can either connect them to the local power supply or a separate generator nearby. The next component is the traffic signal lights, these lights come in three different colors, namely –red, yellow, and green. These lights are attached to a pole so it’s visible to drivers.
The control center, as the name suggests is the centralized unit that controls the whole system. These have a computer inside them that coordinate between all the lights in an intersection.
Lastly, the detectors and sensors provide the control center with information regarding the presence and volume of vehicles on the road. It acts as the eyes & the ears of the system.
Types of Vehicle Detection Sensors in a Traffic Light System
As discussed above, the basic function of a traffic signal system is to regulate the flow of traffic automatically and with the least risk of errors possible. Nobody wants to be responsible for mass vehicular collisions at the nearest four-way intersection. To ensure safe working, we have developed several methods to facilitate the coordinated working of a traffic light system.
So, let’s discuss these systems.
This is one of the oldest methods of controlling traffic signals. Every intersection with lights has a single control hub/machine/computer in a housing nearby that can be programmed to switch lights at specific time intervals.
(B). Induction Loop Sensors
This is the more modern and one of the most widely used signal control systems available nowadays. These systems use a difference in inductance to monitor the presence of vehicles near an intersection. There is a loop of induction coils embedded inside the asphalt connected to a nearby generator/power source. Once powered up, the coils start to build an electromagnetic field with a certain level of inductance. Once a vehicle enters this field, the steel surfaces of the vehicle change the inductance of the field. This change is picked up by the sensors in the system which communicates with the traffic signal.
(C). Radar Detectors
Unlike the previous system, a radar detector works above the ground. These systems utilize microwave signals to detect the movement of vehicles toward and away from them. These are generally mounted on traffic signal poles or arms. However, in order to work, the vehicle must be moving faster than 3 miles per hour/4.8 kilometers per hour.
The biggest issue with these sensors is their need for a direct line of sight with vehicles. Meaning that any obstruction like billboards, adverse weather, etc. Can make these systems not work properly.
(D). Video Camera Sensors
Lastly, some traffic signals utilize video camera detectors to regulate the flow of traffic. These systems use a camera and vehicle detection software/algorithms to identify the presence of vehicles inside a narrow detection zone. These are best for locations where the rads are not properly made like in remote or rural areas.
However, the biggest issue with this system is that they are severely prone to false detections. These sensors can be blinded by headlight flashes and heavy rainfall. They can also trigger false positive detection from the shadow of vehicles.
Frequently Asked Questions
Q1. What is the importance of traffic lights?
Traffic lights allow for the automated regulation of traffic flow. These systems significantly increase the safety of the traffic on our roadways.
Q2. Who discovered traffic lights?
No single person discovered traffic lights, the invention of the modern traffic signal system happened through the hands of four individuals, namely – Garrett Morgan, William Potts, J.P. Knight, and Lester Wire.
Q3. Which LED is used in traffic lights?
Traffic lights use LED lights of three different colors, namely – Red, Yellow, and Green. These lights can be of different power outputs, depending on the area of application.
- Last updated on Jul 01, 2023