There are "Vehicle and Traffic Laws" which say that police vehicles when parked should have police lights to warn people around. This is the warning light law that needs to be followed by every police car.
Police vehicles and Blue Lights
The main purpose of these police lights is to catch the attention of the people. In some countries policemen have blue uniforms and blue police lights and this is one of the main reasons that people associate police men with blue color. The blue color on the polices car helps in making people realize that it is the Police and not any other car with flashing lights. Some police cars do not use siren along with the police lights because the siren can either help the suspect to flee off or he can even arm himself. Moreover, blue color also provides an ease of recognition.
The ambulances also have the blue lights and siren, which they use concurrently. This is because they want to scatter the traffic that comes into their way as they need to take the emergency patients to the hospital. A little delay can harm the patient, so the ambulance uses the siren and blue lights, both. Some people have the conception that why doesnt the police lights include yellow light. Usually, the yellow lights are brought into play by the slow moving vehicles or over dimension loads. So the purpose of yellow light is to alert people from the hazards. The color "red" is used by the firemen, rescue people or the EMS. In some countries, police even uses blue and red lights in combination to signify a higher department than the rescue personnel and firefighters.
There are various equipments available in the category of police lights. Some of these varieties are given below.
Warning Lights
Caution Lights
Emergency LED
Mini Lights Bars
Strobe Beacon
Beacon
Police use Light
LED Module
Rectangular Police lamp
Police Light Electronic Siren
Police Light Bars
Strobe Light
Police Light Manufacturers
There are numerous police light manufacturers around the world that trade police lights through their websites. This makes it easy for the police departments to purchase the necessary police lights from such traders. All they need to do is just choose the from the presented models.
So, if you are driving and a police car passes on by your side with police lights and siren on, make sure you give them a pass.