A Cause for ALARM!

Dec. 28, 2000
Work-zone intrusion alarms help protect crews; lower insurance and workers' compensation premiums may be additional benefits
The statistics tell the tale: In the U.S., workers receive an average of over 25,000 disabling injuries annually in roadway-repair zones; between 600­p;900 workers a year die as a result of these injuries.

Of those killed, 59% die as a direct or indirect result of a vehicle entering a work zone. Work-zone related fatalities have risen sharply over the past several years-the increase from 1992 to 1993 alone was 20%-and the loss of personnel is compounded by the economic loss from these accidents.

And given the current dearth of federal funding for new roads, more and more highway- and bridge-construction workers will find themselves performing maintenance or reconstruction work, in situations where the only barrier between them and traffic is a thin veneer of rubber cones and arrowboards.

However, these safety devices only work if drivers are attentive and have control of their vehicles. While such work-zone safety products do the job they are designed to in an admirable manner, they are passive tools. What is missing is an active tool that will warn workers that an unauthorized vehicle has entered the work zone. With the recent advent of work-zone intrusion alarms, this need has been filled.

The basic principle behind work-zone intrusion alarms is the same for all products currently on the market. A work zone is either mechanically or electronically delineated by the product, and any vehicle intrusion into this zone sets off an aural and/or optical alarm. This gives workers time to see where the breech of the zone has occurred and to take evasive action.

Many work-zone accidents are the result of drivers who have fallen asleep or are operating under the influence. In these instances, the speed of the intruding vehicle can be quite high (especially in highway work zones), and, even with an intrusion-alarm warning, a worker may have only seconds to flee. However, these few seconds are precious: They can make the difference between a "near miss" and a serious injury, or a serious injury and death.

While arrowboards, flag crews and cones can help keep attentive drivers out of work zones, it is the in-attentive driver who poses the greatest risk to work-zone crews. It is the latter category of drivers that intrusion alarms guard against.

Intrusion alarms don't have a lengthy history-most of the products on the market today are either a direct or indirect result of a 1994 Strategic Highway Research Program (SHRP) study. They can be classified into two distinct types: mechanical, in which a vehicle running over a pneumatic tube sets off the alarm (like a gas station bell line); or electrical, where a vehicle entering a work zone breaks a microwave, infrared or other electromagnetic beam and sounds the warning.

Neither system type is inherently "better" than the other; each has its advantages and disadvantages. Mechanical systems are, in general, lower in cost than electronic units, but they are not as flexible. Electrical systems can take advantage of the rapid evolution of computerized technology, whereas mechanical systems are less intimidating to the novice. Each system type shares many common features, such as the ability to string many individual systems together to make a longer protection zone; both are designed to set off an effectively loud warning siren when the work zone is breached.

Kenco International Inc., Ligonier Valley, Pa., makes the Watchdog perimeter-intrusion alarm system. Its a mechanical system that consists of 100-ft-long lengths of pneumatic tubing tied to a siren.

The hose-about the diameter of a garden hose-is wound off a reel that can be mounted on the back of a pickup and placed on the pavement just inside the cones of the work zone. At the actual work site, the junction box at the end of the hose is wired to a siren. This siren, which can be mounted on any metal surface-such as the top of a truck cab-with its magnetic feet, is plugged into a standard cigarette lighter for power. (The unit also comes with battery clips so it can be attached to any 12-volt battery.)

"The hoses are sealed tubes-there is no air going into the tubes," says Bill Douglas, Kenco's marketing manager. "Sensors are located every 100 ft that detect the pressure pulses [from an encroaching vehicle], so a worker is never more than 50 ft away from a sensor. The hose has a nylon-braided sleeve, and a hardwire runs right with the hose that sends the signal back to the alarm."

He says the system can be "daisy chained" with almost any number of units; each 100-ft-length of hose is attached via its junction box to another.

One of the concerns of this type of system is the longevity of the pneumatic hoses, but Douglas says this isn't an issue. "We have dragged these hoses up and down highways; we've given them a lot of heavy use. We figure the life expectancy of the hose is about five years."

The Watchdog system comes with 300 ft of hose, a hose reel, a siren and 100 ft of wire for hose-to-siren connection, and clips and a cigarette-lighter adapter for power. Simple to set up, test (just stomp on each test section) and use, the system runs for $2,295. Options include additional lengths of hose and a strobe light that can be attached to the siren for visual warning.

Electronic-based systems are generally higher priced-high tech often means high prices. One of the higher-profile electronic units on the market today is Traffic Management Systems Corp.'s Myriad Safety Sentinel2 intrusion alarm. Jack Toman, president and CEO of the St. Louis-based company, was a participant in the original SHRP meetings that led to the 1994 intrusion-alarm testing. "When we were originally approached for this project by SHRP, we designed our system to specifically address the high-speed, high-crash risk applications. That is where the vast majority of fatalities and injuries were taking place.

"We looked at maximum warning time as being one of the most important factors, as well as a proactive means to get the word out to all workers within the zone simultaneously, and tried to design it in such a way as to eliminate every potential for falsing."

Toman came up with a system that has three basic units: a microwave transmitter, a microwave receiver and a strobe light (known as a CORS light, for "coded optical-response system").

"Virtually no training is involved in setting it up," Toman explains. "You place the receiver where you want it-by the workers-and then have someone take the transmitter to a point back down the road. You adjust the receiver so it catches the beam of the transmitter-there is a bar graph on the back of the unit-and then lock it down."

This establishes the work-zone edge. Any vehicle or person who strays across this imaginary line will set off the alarm and the CORS light. In addition, Traffic Management's system has a CORS "slave unit" that users can purchase and place at appropriate intervals on top of channelizers along the work zone. When one light goes off, it sends out a digital signal that sets off the next light up the line, which then repeats this operation. This results in a cascade of flashing strobes that, together with the dual 130 dB sirens, clearly indicate that a vehicle has entered the protected zone.

Toman says the basic system costs $4,000; slaves are $1,000. While Toman has yet to have a contractor balk at such a price tag, he has a rejoinder for those who might: "Compare the cost of our units to the loss of even one life."

Because the systems are designed to safeguard workers, concerns about false alarms are a very valid complaint: A system that "cries wolf" too often will not be as effective as one that just detects what it is supposed to. Electronic system are more prone to false alarms than mechanical systems (workers can just step over pneumatic tubes to leave a work zone), but these "bugs" are slowly going away.

For example, the SafetySentinel2 uses a very wide transmitting beam and a very narrow receiver "eye," and this permits a certain degree of "wiggle room." With this arrangement, the channelizers the transmitter and receiver are mounted on can move in the wind or from vibration without the receiver losing sight of the transmitter's beam, which would set off the alarm.

The unit's receiver has a switch that can be depressed to temporarily disable the system, allowing crew members or work vehicles to access or egress the site. This disable button does not lock. A worker has to keep depressing the button manually to keep the system inactive. This is a safety device that is designed to prevent a worker from disabling the system with an "on/off" toggle and then forgetting to activate it once crew members return to work. This could result in just the opposite of a false alarm: a false sense of security, which could have tragic consequences.

Active by nature, the intrusion-alarm systems are gradually integrating other, passive features that enhance worker safety. Traffic Management's system currently has the only fully FCC-approved "drone radar"; this system sends out radar pulses either continuously or sporadically on both K and X bands, setting off virtually every car radar detector on the market.

This serves two purposes: It slows cars down before they even reach the work zone, and drivers have already been warned that something is ahead, so they are more likely to notice the other passive systems, such as arrowboards.

Toman says a new option the company offers is an excessive-speed module that will measure the speed of approaching vehicles. While this may seem like a needless frill, it is useful in that this option allows users to set a threshold of approaching-vehicle speed to set off the system. For example, a car traveling 85 mph in a 45 mph zone is an accident waiting to happen; by triggering the alarm at that threshold, workers can clear the site before the vehicle is near.

Manufacturers are learning from each other, as well. Toman says his company's unit now includes a pneumatic tube that provides protection perpendicular to the work zone at the taper. This component, much like the one that the Kenco system uses, is integrated into the rest of the company's system, so a vehicle running over the hose at the taper will set off the full warning system.

On the other hand, Douglas says Kenco is considering adding an optional feature similar to drone radar for the Watchdog units. He says interest is high for this type of device, and it will probably be available by this fall. Another feature he expects to market is a siren that is integrated right into a light bar, for an aural and visual warning. Again, this is a step Traffic Management has already taken with their system.

"Keeping up with the Joneses" seems to be a big part of this rapidly expanding market; Traffic Management has gone as far as planning a recall of its earlier units. "I haven't actually put out the letter yet," Toman says, "but I plan to issue a recall of my earlier versions of the equipment and replace them, free of charge, with the updated model. That's going to cost a lot, but, in the long run, I believe it will be beneficial to us."

Putting the best foot forward in this young market appears to be a wise game plan-both Douglas and Toman expect this market to grow tremendously in the near future. Both believe the underlying push will come from states, which will write specifications for the intrusion alarms into contracts. Once the states are on board, insurance companies may well follow suit.

And then there is the question of litigation. "We heard from a lawyer who wanted to know if [intrusion-alarm systems] were out when his client was hurt," Douglas recalls. "He said he could use something like that against the contractor for the suit. I think this type of litigation is something contractors are going to have to look out for in the very near future."

Toman recounts a similar story, and adds that he expects intrusion alarms to be included in the Manual on Uniform Traffic Control Devices (more commonly known as MUTCD), much as arrowboards have been, within the "next couple of years." Since MUTCD is a document of legal standing-it is often used as part of tort lawsuits-inclusion in the manual will all but force contractors to use intrusion alarms.

While the use of intrusion alarms may become commonplace for the wrong reason-fear of litigation vs. fear of personnel loss-the safety of those working in construction zones is the real bottom line for intrusion-alarm use.

Yet even with the most elaborate series of safety devices, the average worker is still very vulnerable. Recognizing this reality, Kenco has taken the somewhat unprecedented step of putting aside approximately 5% of the proceeds from the sales of its Watchdog units to establish a fund for the families of work-zone accident victims.

"At the end of this year we will take a look as some individual cases we have heard about and decide where to distribute the funds," Douglas says. "There is no actual charity for work-zone accident victims; this is it. If my competitors want to get together with me and do the same, I'll be glad to work with them. Right now, there isn't a lot of cash in the fund-the system is still so new-but it could be substantial if sales take off the way I hope and expect them to."

If the makers of intrusion alarms had it their way, the alarms would be so effective and profitable that such a fund would swell to an unbelievable amount-but there wouldn't be anyone left who "qualified" to receive this largesse.

About the Author

Lee Geistlinger

Sponsored Recommendations

Get Utility Project Solutions

June 13, 2024
Lightweight, durable fiberglass conduit provides engineering benefits, performance and drives savings for successful utility project outcomes.

Energy Efficient System Design for WWTPs

May 24, 2024
System splitting with adaptive control reduces electrical, maintenance, and initial investment costs.

Meeting the Demands of Wastewater Treatment Plants

May 24, 2024
KAESER understands the important requirements wastewater treatment plant designers and operators consider when evaluating and selecting blowers and compressed air equipment. In...

Modernize OT Cybersecurity to Mitigate Risk

April 25, 2024
Rockwell Automation supports industry-leading Consumer Packaged Goods company, Church & Dwight, along their industrial cybersecurity journey.