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8 Work Zone Safety

8.4 Downstream Hazard Warning

8.4.1 Wizard CB Alert System – Iowa, Kansas and Missouri

The information on the Wizard CB Alert System was obtained from the Midwest States Smart Work Zone Deployment Initiative Year One Report.22

Impetus for the Activity

The States of Iowa, Kansas, Missouri and Nebraska formed the Midwest States Smart Work Zone Deployment Initiative to test and evaluate technologies for improving safety and efficiency of traffic operations in work zones. By working together, the agencies avoid unnecessary duplication of research through sharing of research results.

Criteria for System Selection (Hardware and Software)

The group held a series of three workshops to identify work zone problems, to define solutions and to select the technologies for evaluation. Potential solutions were presented by technology providers, and these solutions were matched with work zones on specific construction projects. The Wizard CB Alert System, provided by TRAFCON Industries, Inc. was matched with work zones in Iowa, Kansas and Missouri.

Description of the System

The Wizard CB Alert System is used to automatically broadcast advisory messages to warn drivers of traffic or road conditions/hazards ahead. The system broadcasts a pre-recorded or recorded on-site message on a CB channel, usually channel 19. Message length can vary, but messages are typically 7 to 10 seconds and are broadcast every 30, 60 or 90 seconds, as set by the user. In order to avoid interfering with others using the channel, the system monitors the activity and broadcasts when the channel is free. The range of the system is about 6 km. Drivers must have a CB radio and have it turned on to the broadcast channel to receive the message. The system consists of a Wizard Work Zone Alert and Information Radio, a standard CB antenna and a 12-volt power source, and is often trailer mounted. The purpose of the system is to give advance warning of upcoming delays (and associated queued vehicles) to the drivers of heavy trucks to enable them to stop safely. The system can store up to three messages and can broadcast over 2 channels.

In Iowa, the system was used in July 1999 during a striping operation on a rural section of I-35. A message advising drivers of the striping operation was broadcast on Channel 19 every 30 seconds.

In Kansas, the system was used in 1999 for a work zone on a rural section of I-135. The work zone involved a lane closure leading to a median crossover. A message was broadcast advising drivers of the lane closure ahead.

In Missouri, the system was used in April, 1999 for a work zone on a rural section of I-70. The work zone was a stationary, long-term work zone that involved a lane closure. A message was broadcast to advise drivers of the lane closure and warning them to watch for slow or stopped traffic. Objectives included:

System Performance
No problems with system performance were noted in the Iowa report. There were reported problems with data collection equipment in the Kansas report, but no mention of problems with the Wizard CB Alert system’s performance. Missouri also experience system performance problems with the data collection equipment, but no problems with the advisory system’s performance were noted.

System Effectiveness Evaluation

The system was formally evaluated in Iowa, Kansas and Missouri.

In Iowa, the system was found to be quite effective at warning truck drivers about the presence of the striping operation ahead. Measures of effectiveness included positive comments from drivers and survey responses on the topics of whether the drivers heard the announcement, whether they thought the message was effective at warning them about the paint crew, whether they thought the message was annoying, and whether they thought that the system’s continued use in the future would be useful.

Many positive comments were recorded from truck drivers over the CB system. The survey results were as follows:

In Kansas, Measures of Effectiveness included lane distribution of trucks upstream of the project and truck speeds upstream of the project. Although no statistically discernable changes occurred in either of the measures when the system was deployed, the evaluation team felt that the system is intuitively an excellent means of providing commercial vehicle operators with advanced warning of unusual highway and traffic conditions. The team noted that the traffic and roadway conditions at the study site did not place a lot of demands on drivers.

In Missouri, Measures of Effectiveness included:

Note: * Primary Measure of Effectiveness

The evaluation team found that with the system deployed, there were improved lane distributions in advance of the lane closure (percentages of vehicles in the closed lane were significantly lower), and mean speeds were lower by about 3 km/h near the lane closure taper. The survey responses showed that a high proportion of truck drivers received the message and appreciated receiving the warning. The evaluation team did not observe any significant changes in speed variance. No accidents were found to have occurred because of the CB message. The team noted that no lane closures are required for system set-up, operation or removal.

Obstacles and Lessons Learned

The Kansas evaluation team noted that for conditions of level terrain and good visibility, there is little need for improvements to common traffic control measures.

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