Yes it is. Have grown up with the "Q" on fire engines and it is the most effective way to move traffic. I even have one on my pov, a 2001 cvpi, along with an electronic siren. The electronic siren is good, but not as a stand alone piece of warning equipment. With todays new sound proof autos and people who just dont pay attention to emergency equipment, be it fire police and ems. People dont pay attention and we need all the help we can get. So the anwser to the question is YES to the "Q"
i feel it is a necessary item on engines and other large rucks because in todays world there is so many distractions to drivers like cellphones tvs in cars and loud radios. You also have to remember everybody is building vehicles tighter and more soundproof . In traffic the Q is a must , you have to remember you cant stop a engine like a car. Yes they are costly but you can get them off old vehicles and reinstall on new vehicles. The cost is small if it keeps one 175,000 pumper out of a accident
If your looking to move traffic, get a rumbler...mostly on police cars...It is a speaker in the front wich vibrates the ground so if the driver of the vehicle cant her the siren, they will feel their car shaking.