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Can Police Cars Change Traffic Lights?

Can Police Cars Change Traffic Lights?

Many people wonder to see a changing traffic light whenever they hear a siren of emergency vehiclesincluding ambulances or police cars.

Can Police Cars Change Traffic Lights? Police cars can change traffic lights because local government and traffic authorities allow them to turn a red signal to green. It helps them quickly reach a crime site or accident location so that the culprit does not run away. Moreover, traffic light pre-emption helps vehicles that need a clear intersectional road to reach an emergency site. Furthermore, it ensures the security of pedestrians and vehicles on the road and gives a better response time for a signal to turn green within 10 to 20 seconds.

Police cars are included in emergency vehicles that must reach a destination in a hurry. Long lines of vehicles on the road can be a reason to get late, even for hours.

Furthermore, local governments have made specific rules that provide authority to these vehicles to create a passage on a busy road.

What type of vehicles can change traffic lights?

Many emergency vehicles have the authority to make their way through a busy road by using the flashing lights and rays that allow front vehicles to move.

Fire trucks

Firetrucks are meant to fight a fire, equipped with water hoses and firefighting apparatus.

They have to reach quickly a location that can be a home wrapped by high flames or an office building that has caught fire due to a short circuit.

Moreover, this emergency vehicle can be required on the highway to blow out fire from an exploded car. So, they have to cross a large mass of vehicles present on the city roads.

These are larger than emergency vehicles like police cars and need a clear road or wide passage to pass through.

Therefore, regulatory authorities have allowed them to use traffic signal preemption to reach the fire location in time before it becomes difficult to control.

Police cars

Cop cars are also included in the emergency vehicles as they must reach the crime spot before the culprit runs away. Therefore, it is essential to clear the road and make way for these to go at a reasonable speed.

Moreover, it is dangerous to cross the intersections in a hurry; that’s why they use sirens and strobe lights on a vehicle to turn the red signal into green.

The siren and flashing lights on the vehicle can help make pedestrians aware of the incoming cop car so that they can make the road clear for them to pass.

City buses

These buses are not included in the category of emergency vehicles but are given priority on the road. It is essential to give them a priority to avoid inconvenience for office-going people.

Many people use buses or public transport to reach their offices. Therefore, bus drivers can also use this to avoid delays due to red intersectional signals.

It helps increase the reliability of the bus service as it will not get stuck on busy roads.

Moreover, it is considered a strategy by the management authorities to improve the public transport service for people who are using it daily.

It makes the bus service an attractive mode of transportation by making it a fast and reliable source to move in different areas.


Ambulances have to reach the hospital as they carry severe patients who need urgent treatment.

Moreover, these ambulances have to reach apartments quickly to pick up patients having severe heart attacks or take them to hospitals in no time.

So, these can control these signals by turning on the strobe light present installed on them.

Sometimes, they ask for preemption from traffic controllers managing the signals to turn them green and move with caution.


Snowplows clear the snowy roads when bigger piles of snow accumulate on the road and disrupt vehicles flow. It can face delays when there are long lanes of automobiles at the signal.

Moreover, they have to wait for a long until the signal turns green, which can create difficulty for drivers stuck in the snow.

So, it facilitate such vehicles to control conditions on the road as these are equipped with high technology that can efficiently remove snow from roads.

Emergency vehicles

Some other emergency vehicles can change signal lights in their favor.

For example, traffic control officers have the right to turn the signal green if there are many vehicles at the intersection to manage the condition.

In addition, an incident response vehicle (IRV) can also make use of this preemption authorized by the local government and reach immediately at a spot of traffic accident.

Furthermore, they can efficiently restore the flow of vehicles by maintaining the safety and security of the drivers sharing a common road and recovering a road network for better flow.

Why do police cars change traffic lights?

There are many reasons for police cars to change the lights on a traffic signal, like when hurrying to a particular destination.

For safe driving

It ensures a safe way of driving as they do not have to quarrel or argue with someone driving in front of cop cars to clear their way.

Moreover, they have to face several rude comments from the public when trying to cross the vehicles in a hurry.

It can also risk pedestrians and vehicles moving on an opposite road with a green signal. When they try to cross a road at an intersection, there is a significant risk of injury or accident.

So, it allows them to use their authority and drive safely on the road.

To reach the emergency site quickly

Police cars change the signal from red to green when they have to reach a location in an emergency. Delayed entry of police at a crime spot can allow the culprit to leave the ground.

They need to reach an accident or murder site to get control over the situation in a better manner.

So, they use their right to use strobe lights or sirens on their vehicles to get through busy roads.

To validate traffic

These automobiles are included in the category of emergency vehicles and validated by the controllers.

Therefore, they have any authority to make a way or ask controllers to clear the lane by turning the signal green.

Opticom helps validate these automobiles as emergency vehicles, which sends a coded signal of infrared rays towards the sensor.

So, the sensor detects specific infrared rays and allows the vehicles to move from a particular lane. This way, they can validate themselves in massive traffic to get their way.

To clear intersections

Intersections are a difficult way to cross as it is a bottleneck that disrupts a smooth flow of traffic. In addition, it is a significant spot of accidents and vehicle conflicts as it joins two opposite roads.

The use of loud sirens having specific volume and tone makes them able to be recognized by the sensors on the signal pole at intersections.

A quick signal light change makes it easy for them to move forward without bumping into any other vehicle or a person crossing the road.

Moreover, the traffic begins to move on the road, having police cars at intersections, and the one on the opposite road stops immediately.

Reduce response time

They change signal lights to change the response time from the sensors instead of waiting for the opposite side vehicles to move.

They can modulate the signal quickly without waiting as it makes them able to cut almost 20% to 30% of the response time and reach their destination quickly.

So, it helps them reduce the response time of sensors which take a few minutes usually, and change them quickly.

How do police cars change traffic lights?

There are different ways to change traffic lights when they are stuck in large lanes on the roads that can be adopted by police cars.

Opticom is a control system that transmits infrared rays to optical sensors on the pole that allow the movement of automobiles.

There are strobe lights on vehicles which are detected by an optical sensor on the traffic signals and capture rays from the oncoming vehicle.

The signal light changes its color after recognizing an invisible spectrum of light. In addition, some sensors recognize the loud sound of a siren.

These sensors are connected to electronic devices which can send a call to the controller in the cabinet and change signal color.  

Only authorized people are permitted to turn strobe lights on and change traffic signals. Some people add infrared rays transmitters to their vehicles but are not allowed to do so.

In addition, some specific light patterns on cop cars, the sound of a siren, radio waves, and infrared rays are transmitted that can modulate the signal lights.

How much time do police cars take to change traffic lights?

It is not difficult to change traffic signals as you need to turn on the switch to allow the flashing of strobe lights. The sensors take only a few seconds to capture and modulate the signal light.

Almost 10 to 20 seconds are sufficient for transmitting light to the sensor. The police cars turn on the strobe lights and siren when these are at a small distance away from the signal.

Accordingly, it allows sensors to detect specific waves in an incoming vehicle and produce a response quickly.

I have seen a quick traffic signal change when a cop car gets closer to it and turns green from red within a short time.

What do drivers say about this?

I surveyed 591 drivers to know whether it is true that police cars can change the traffic light signal or if there is nothing real in it.

Out of 591 drivers, 397 people (67%) said it is true that emergency vehicles, including police cars, can change these signals.

However, 142 people (24%) said only ambulances are allowed to turn the signals green, as these automobiles can only use their siren to make a road clear.

While the remaining 52 people (9%) said they had never seen a cop car while changing signals, so they had no idea about it.

Police officers can turn on the strobe light to change the traffic signal to make a clear passage on a busy road.

I wondered how traffic lights turned green when the police car arrived, but I learned from a policeman that it was not just a coincidence.”

All emergency vehicles have a right to turn signals green, including ambulances and buses.

“I was standing for a few minutes in the long lane at the intersection yesterday, and the signal was red, but it turned green quickly when an ambulance arrived.”

“I worked as a firetruck driver for many years, so I know they are taught to use traffic signal preemption at intersections.”

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