Work Zone Mobility and Safety Program
Photo collage: temporary lane closure, road marking installation, cone with mounted warning light, and drum separated work zones.
Office of Operations 21st Century Operations Using 21st Century Technologies

Iowa's Evaluation of the Wizard CB Alert System

Ali Kamyab, Research Scientist

Center for Transportation Research and Education

Iowa State University

Ames, Iowa 50010

T. H. Maze

Former Director of the Center for Transportation Research and Education

Currently Vice President for Transportation Services

Howard R. Green Company

St. Paul, Minnesota 55108


This paper reports on the evaluation of one technology intended to manage vehicle speed in and around work zones on interstate highways. The technology tested is the Wizard CB Alert System. Other technologies were tested as part of an Iowa Department of Transportation (Iowa DOT) sponsored evaluation of three technologies. The other two are reported elsewhere. The Wizard CB Alert System is a device that continuously broadcasts a warning message over Citizen Band radio warning approaching drivers of the work zone ahead.

The Iowa DOT test is part of a Federal Highway Administration (FHWA) pooled fund study involving the State Transportation Agencies in Iowa, Kansas, Missouri, and Nebraska. The pooled fund study, called the Midwest States Smart Work Zone Deployment Initiative (MwSWZDI). The goal of the project is to develop better ways of controlling traffic through work zones, which improves traffic safety and traffic operating efficiency of work zones. To achieve this goal, the program is evaluating or has evaluated a myriad of technologies for the management and control of traffic through work zones. The Iowa DOT worked with the Center for Transportation Research and Education (CTRE) on the evaluation of technologies of interest to the Iowa DOT. CTRE evaluated the Wizard CB Alert System (CB Wizard) during the summer of 1999. The purpose of the evaluation was to determine if the CB Wizard could successfully assist in controlling traffic along moving work zones on interstate highways. The evaluations were largely subjective but very positive results were achieved.

Wizard CB Alert System

The Wizard Work Zone Alert and Information Radio was designed and patented by Highway Technologies inc. and built and marketed by TRAFCON Industries Inc. A picture of the device evaluated in Iowa is shown in Figure 1. It is designed to give drivers monitoring the CB radio advanced warning of upcoming delays at construction sites or incidents. The advanced warning will allow drivers the opportunity to moderate their speed and become observant of the need to slow, stop, or maneuver before they reach the work zone or encounter queues of halted vehicles. Since truck operators most commonly monitor CB radios, it was assumed that the CB Wizard would have the most impact on truck drivers. On rural Iowa interstate highways, large trucks are a significant portion of the traffic volume (as much as a third) and, due to their size and weight, their intrusion into the work zone is more dangerous than it is with other vehicles. The system was developed at the request of the Pennsylvania Department of Transportation.

In July 1999 the CB Wizard was used in conjunction with a work project performed by an Iowa DOT striping crew on Interstate Highway 35. The purpose of this field test was to determine if CB Wizard assists in advanced warning of a lane closure for truck operators.

Evaluation Case Study

The painting crew consists of four to five vehicles spread out over approximately one mile and traveling at 25 miles per hour (MPH). The lead vehicle is the stripping truck and the trailing vehicle is a pickup truck that carries a flashing sign that reads "CENTERLINE/EDGELINE PAINTING AHEAD." The CB Wizard was placed in the trailing vehicle to extend the CB signal as far upstream as possible to maximize the amount of time between the warning message and approaching the rear most vehicle.

The CB Wizard was set to broadcast a warning message on CB channel 19, the most commonly used frequency by truck drivers. A 30-second interval between broadcasts of the warning message was selected to ensure that the message was broadcast frequently enough so that truckers would hear the message at least once while approaching the work zone.

Figure 1, Wizard CB Alert System

Evaluation Procedure

Since the purpose for using the technology was to alert drivers of the approaching moving work zone we really had two issues to evaluate. The first one was whether drivers were actually received the message and secondly, was the message delivered effective in alerting drivers to the approaching slow moving vehicles.    The first issue deals with determining what proportion of the truck drivers actually heard the warning. Because we had no means to stop trucks on the Interstate and ask 100 percent of the operators if they hear the warning, we chose to ask a sample of truck operators that stopped at a rest stop down stream from the moving work zone and assumed that the truck operators that stopped at the rest stop were representative of the entire population. To determine how effective the warning was, we decided to monitor the truck operator comments over the CB radio and interview truck operators at the down stream rest stop to determine their opinion regarding the advanced warning system's message. We would have liked to have had an analytical measure of the systems impacts on speed in and around the work zone, but the movement in the work zone makes measuring the speed of approaching vehicles difficult and costly.

To perform the evaluation, two people were used to collect data. One person stayed with the CB Wizard in the tailing vehicle of the interstate paint crew.  This person monitored the CB radio, listening for comments from truck operators regarding the CB wizard.

The CB Wizard was set to broadcast over CB channel 19, the frequency truck operators most commonly monitor. An interval between broadcasts of thirty seconds was selected to ensure that approaching truck operators heard the message at least once. The message was not broadcast over a second channel. 

The content of the message transmitted greatly impacts the effectiveness of the system. Over the course of the test, the message that was used to warn truck drivers was altered based on the suggestions of truck operators.  The first variation of the message had the following content and was read using a very official and authoritative voice:

"This is the Iowa DOT. Slow-moving paint operation in the right lane of northbound Interstate 35. Please use caution."

The above message worked, but truck operators suggested that the effectiveness of the message could be improved if a location for the work zone was identified.  The second variation of the message became:

"This is the Iowa DOT. Slow-moving painting operation in the right lane of northbound Interstate 35 - milepost 160 to milepost 170. Please use caution."

Although the second message was a little longer, it became much clearer.  Milepost ranges were normally announced in five to ten mile intervals. The smaller the range, the more useful the message became. However, this would mean more work for the operator to update the message more often.

In an attempt to reduce the amount of time spent on recording and changing the CB message, the announcement was changed to give a relative location rather than a specific location of the paint crew. The new message became:

"This the Iowa DOT. Northbound drivers on Interstate 35, you are approaching a slow-moving paint crew in the right lane. Please use caution."

This message was very successful. The only suggestions one truck operator had was that some drivers might tune out the message once they heard "Iowa DOT" thinking that the message might be from the Iowa DOT's commercial vehicle enforcement officers. Therefore, the final message was changed to:

"This is an Iowa DOT road work alert. Northbound drivers on Interstate 35, you are approaching a slow-moving paint crew in the right lane. Please use caution."

The last message concisely presented all the pertinent information. Also, the message would only need to be changed when the paint crew changed direction or changed roadway.

CB Radio Comments

Most of the comments expressed by truck operators over the CB radio related to the roadwork itself rather than the message. Many truck operators expressed their disapproval of the time or location that work was taking place. However, many truckers did notice that the CB message was something new and different and the following are representative of the positive and negative comments:

Positive Comments

  • "That must be a recorded message."
  • "Okey-dokey!"
  • "That's what I think all states ought to do - get on the CB and warn you about this stuff."
  • "OK, thank you."
  • "Thanks for the info. I appreciate that."
  • "Thank you - and we will (use caution)."
  • "Allrighty!"
  • "Thank you, sir."
  • "That's the first time I've ever heard anything like that. I wish everyone would do that. It'd make things a lot easier."
  • "That was a recording. They must change the mile markers on that."
  • "That's pretty good. I've never heard that before. That's smart."
  • "Thank you for that!"
  • "Hey, whoever says that on the radio, it sure saves a lot of hassle."
  • "They ought to do a lot more of that."
  • "Thank you all. I appreciate it. I'll see you up there."
  • "That's a good idea."
  • "I wish more states would start using the CB radio like this."
  • "Yeah, that's the first time I've heard something like that."
  • "Throw a milepost in there and you'd have it right."

Negative Comments

  • "You've got enough trucks and signs out there. You don't need to tell us this stuff every five seconds!"
  • "Get off my radio. You need to get on a regular radio station and warn those four wheelers."

Rest Area Survey

A data collector was located at a rest area upstream from the mobile work zone and positioned in a location near the truck parking. The individual stopped truck operators, identified himself/herself as data collector for an Iowa DOT research project, and asked them if they would answer a few questions.  Most truck operators were willing to take the time to answer our questions but some were not. For willing participants, the interviewer had a few set questions. They were:

  1. How many years of professional driving experience do you have?
  2. Do you have a CB radio in your truck?
  3. Did you see the paint crew on the interstate and if so what alerted you first to the paint crew?
  4. Did you hear the CB announcement regarding the paint striping crew and on what channel?
  5. Did you think the message was an effective warning?
  6. Was the message obtrusive or annoying?
  7. This system may be used more often in the future. Do you think this would be helpful?

Over the course of six days, the interviewer was able to interview a total of 94 truck operators. Of the drivers surveyed, 88 (94%) had a CB radio in their truck. Of those, 70 (80%) had their radios tuned to channel 19. Of these 70 truck operators, 59 of them (84%) saw the paint crew on the interstate.  Thus, 59 truck operators out of 94 (63%) had their CB radios tuned to channel 19 as they passed the paint crew on the interstate. The following are the results of what the 59 truck operators that had their CB radio tuned to channel 19 and passed the paint crew said alerted them first to the paint crew:

CB Alert Message 24   (41%)
Lights on Trucks 14   (24%)
Signs 10   (17%)
Arrow Board  7   (12%)
Other Truck Drivers   4     (7%)
Total 59 (100%)

Of the 59 Truck operators, 44 (75%) stated that they heard the CB Wizard message, although it may have not been the first indication that they were approaching the paint crew. Of the 44 truck operators that heard the announcement, 39 (89%) thought the message effectively warned them of the paint crew. When asked if the message was obtrusive or annoying, 43 of the 44 truck operators answer no. Finally, when asked if they thought the system's use should be continued future, all 44 answered yes.

The following are some of the comments truck drivers gave when asked their opinion of the CB Wizard alert:

Positive Comments

  • "If late at night, hearing something like this come on may help alert drivers."
  • "Anything like this is helpful."
  • "This could save accidents from happening."
  • "It gives us better preparation - especially if coming up over a hill."
  • "Cars notice when trucks move over. Hopefully it would prevent any rear-end collisions."
  • "Neat idea!  More states should use this!"
  • "Every little bit helps, but flashing signs alert the most."
  • "This alerts everybody. It's a good idea."
  • "You know what's going on ahead of time."
  • "The paint crew is moving all the time. You never know where they'll be. It helps."
  • "I loved it!  I got into the left lane right away - over two miles before the paint crew."
  • "It is a good idea. Police should use this for accidents. The paint crew was over a hill and I heard the message before I even saw them."
  • "Other states should learn how to use this. I have also heard it on I-70 in Missouri."
  • "No complaints. It worked really well. Everyone was merging."
  • "It's great. It's good for those without radios, too, because if trucks slow down, cars will too."
  • "It's a good idea if used right with useful information."
  • "It is very effective because I heard it before I got to the paint crew."
  • "If it helps save a life or prevent an accident, it's worth it.  I liked how clear it was. Great idea."
  • "It doesn't hurt anything."
  • "The CB is used for communication. Any time you have advanced warning, it's helpful."
  • "It seems to work well in Missouri where they use it a lot."
  • "Advanced notice is the ideal."
  • "Good idea. This kind of thing is the only reason I listen to the radio."
  • "I knew it was a recording, so I thought it must be important.  It made me listen and be aware of the situation."
  • "I argued with another guy who thought it was a joke. It is a very good idea."
  • "It's definitely helpful at alerting drivers. They should use it at all construction zones and have state troopers there to slow down four-wheelers."
  • "A good idea, but sooner (warning) would help."
  • "You know what's going on before you get there. You should notify truckers even sooner."
  • "The message wasn't loud enough. It'd be more effective if drivers going the other way would warn truckers."
  • "Make it louder or more powerful. Also use it in construction zones and for snow removal."

Negative Comments

  • "Use caution?  How do you use caution?"
  • "Are truckers the only dumb ones that need to be warned?  You need to warn cars, too."


Our evaluation of the Wizard CB Alert System resulted in very positive findings.  We found that the device was effective in warning truck operators of approaching mobile work zones. Sixty- three percent of the truck operators that had their CB radio tuned to channel 19 as they passed the paint crew heard the Wizard CB Alert message and 41 percent stated that the CB message was their first indication that they were approaching the paint crew. The system reached a large portion of the target audience and passed on information that was important to its listeners. Many truck operators voiced their approval for the system, showing their support for its continued use in the future, and even suggesting additional situations where the system would be helpful.


We would like to thank the Office of Traffic and Safety at the Iowa DOT for their support of this project and Midwest States Smart Work Zone Deployment Initiative FHWA pool funded study for their institutional support. The Midwest State Smart Work Zone Deployment Initiative's home is at the Mid-America Transportation Center at the University of Nebraska - Lincoln.

Office of Operations