Rumbler rattles motorists alert

     Getting a driver's attention today can be nearly impossible. Loud music, cell phones, fans blowing and maybe even children bickering in the backseat distract today's drivers. With the Rumbler Intersection-Clearing System, Federal Signal makes the nearly impossible, possible.

     While the primary siren and warning lights on an emergency vehicle remain critical, the Rumbler attracts attention by being heard — and felt.

     "The idea came up that people were cocooning themselves so much inside their vehicles that in some cases, the siren and lights didn't seem to be enough," says Tom Morgan, police market vice president at Federal Signal Corp. Morgan credits Capt. James Wells of the Florida Highway Patrol for coming up with the original idea that a supplemental warning system was needed to get people to pay more attention to emergency vehicles.

     The Rumbler attracts attention by creating a vibration. The lower frequency tones of the Rumbler penetrate and shake solid materials, allowing drivers and nearby pedestrians to feel the sound waves (and possibly see the effects on a shaking rearview mirror).

     After the Rumbler is activated, people have a tendency to look up and check their rearview mirror to see what's causing the vibration, Morgan describes. Once the Rumbler has a motorist's attention, he or she should see the warning lights of the emergency vehicle behind them. The driver becomes aware a regular siren was going off (though the individual's ears were receiving the audible siren, his or her brain wasn't quite processing it with all the other distractions going on in the vehicle) and pulls over.

     Less than two years old, the Rumbler is currently used by about 60 law enforcement agencies. The Rumbler is most common in densely populated metropolitan areas on the East Coast. Morgan points out the Rumbler is sometimes perceived as more effective in larger communities than smaller communities.

     "The communities that have the densest traffic are really seeing value," he says.

     Intersections are particularly dangerous and the Rumbler helps focus motorists' attention on the police car. On the highway, law enforcement officers use the Rumbler in heavier traffic, when an officer needs to clear the lane in front of him.

     Although a supplemental warning system is an extra cost to law enforcement agencies, Morgan points out that by helping officers avoid traffic crashes, it helps them save money, and better protects citizens and officers alike.

     "I think the main benefit is improved safety," he emphasizes. "Particularly in high-risk situations, such as intersections or heavy highway traffic."

Rumbler reactions

     Within about 200 feet in most cases, the Rumbler will at least cause a driver to look up, but response to the Rumbler can differ. Morgan has observed different reactions during demonstrations. In one case, a person really felt it while the person next to him felt it, but not as much.

     "Different people do respond in different ways to that lower frequency," Morgan says.

     People attending demonstrations have said they were expecting the Rumbler to really jolt them. However, Morgan explains that a jolt is not the intended effect, but rather the Rumbler is meant to be less shocking. The subtle vibration should cause motorists to look up and pay attention.

     Some people say the sound emitted is annoying but most police officers consider that effect to be positive, he says. Even if it annoyed motorists, the vibration captured their attention.

     Other reactions characterized the Rumbler as louder than a regular siren, which Morgan refutes, explaining that the Rumbler actually operates at about 10 dB less than the traditional, primary siren.

     "I think some people expect it to be like somebody pulling up to them with a boom box going so loud that they see everything start to vibrate around them," he says. "Although it operates on the same kind of principle at the lower frequency, it's more subtle than that."

     In comparison, thunder is 120 dB, and a primary siren (measured in highly controlled circumstances about 10 feet from the siren — in steady air) is normally 119 dB.

     "In a street environment where you're 20 to 30 feet away, you're actually detecting less than 119 dB," he says. "The Rumbler is about 10 dB below that, in the 109 dB range, which is just a little louder than some traffic patterns."

The system

     A complete Rumbler Intersection-Clearing System includes an amplifier, a timer, two subwoofers and vehicle-specific mounting hardware.

     Another electronic siren, a primary (100/200-watt) siren, must be in place for the Rumbler to work. (The Rumbler cannot be used with mechanical sirens.) The system reads the output of the primary siren, duplicates it, but drops it to a lower frequency (reducing it by two octaves), and amplifies the sound through two high-output woofers. Morgan says the primary siren and Rumbler work together like a duet.

     Anyone who installs other police speaker or siren systems can install the Rumbler. The speakers, a little larger than a coffee can, are installed in the wheel wells. Controls mount under the hood or in the trunk of the car.

     The Rumbler was designed for installation in Crown Vics, but has been installed in SUVs as well as Chargers and Impalas. In the future, Morgan says the Rumbler will be made smaller to fit into smaller vehicles. Federal Signal is also working to reduce costs.

Fleet feedback

     The Metropolitan Police Department in Washington, D.C., has 79 new marked vehicles (2008 Crown Vics and 2007 Impalas) equipped with the Rumbler.

     "People are hearing sirens all the time and nobody is paying attention," D.C. Fleet Manager Greg Hester says, but the Rumbler is something different that causes people to look up.

     "I'm not sure that it's the noise that the people are hearing, but it's something different," he says.

     As a result, he says the greatest benefit is officers are able to be identified more easily when approaching intersections.

     Morgan advises officers not to run the Rumbler unnecessarily. Like anything else, people could start filtering it out. That's why the Rumbler shuts off after 8 seconds.

     "If you use the Rumbler in the appropriate situations, the heavier traffic, the intersections, it has more impact," he says. "Then it becomes something truly different in the environment."

     About a year ago, D.C. police tested a Rumbler system near Gallaudet University, a world leader in liberal education and career development for undergraduate students who are deaf and hard of hearing.

     Police sirens previously were not heard there.

     As a great concern, officers with the Rumbler say it has helped people in crosswalks identify an approaching vehicle that needs the emergency right of way, he reports.

     "All new cars are going to be equipped with the Rumbler," Hester says. "That's how pleased we are."

     North Reading, Massachusetts, has had the Rumbler in its police vehicles for approximately two years. The city's police department has five of its 10-car Crown Vic fleet carrying the Rumbler, and each new vehicle has the system installed — including unmarked units.

     "I think it's phenomenal," says North Reading Police Department fleet manager Sgt. Tom Romeo. "If it saves one collision, every unit has just paid for itself. And that's the way I look at it."

     In California, the Elk Grove Police Department had the Rumbler installed in its new Dodge Charger about six months ago.

     "The most important benefit of the Rumbler is having the added safety feature when clearing intersections or rolling Code 3," says Lt. Craig Potter of the Elk Grove Police Department, who oversees the department's fleet services. "The officers love the Rumbler and wish we had it installed on all of our patrol cars."

     The Elk Grove Police Department is installing the Rumbler in its vehicles, as its 64 marked-vehicle fleet is replaced with new vehicles.

Is the Rumbler right for you?

     Looking to the future, Romeo predicts the Rumbler will continue to gain popularity.

     For agencies that don't have the Rumbler, Romeo suggests they try it. Federal Signal welcomes interested departments to test or get a demonstration of the Rumbler. Morgan emphasizes the Rumbler is most effective in dense urban environments with heavy vehicle and pedestrian traffic.

     "I believe that everyone understands that we have really isolated ourselves in our vehicles," Morgan says. "That increases the risk to an officer and to the citizens in an area where an emergency is occurring. I think people relate to that."

     Rebecca Kanable has been writing about law enforcement issues for approximately 10 years. She can be reached at