In Greenwood, Nebraska a survey of travelers indicated that 29 percent of drivers who remembered DMS messages at a work zone on I-80 thought the alternate route information provided was not useful; 23 percent thought the caution messages were not useful.
The DMS was located nine miles upstream of the work zone and was preset to display two types of messages depending on traffic speeds detected. If only one or two vehicles were traveling less than 25 mi/h in the work zone, then the DMS flashed the following two-phased message: "ROAD WORK AHEAD" / "PLEASE USE CAUTION". If three or more vehicles were traveling less than 25 mi/h, then the DMS displayed the following message for a period of 10 minutes: "DELAYS!! PLEASE USE ALT ROUTE". The diversion point for the alternative route was about one mile downstream of the DMS. Traffic was routed from I-80, to H-31, to Route-6, and back to I-80 downstream of the work zone.
Pneumatic vehicle counter/classifiers were installed 500 and 1500 feet in advance of the work zone lane closure taper in order to collected traffic speed and lane distribution data "with" and "without" the system in operation. During afternoon peak periods, the mainline, the exit ramp, and the DMS were video taped simultaneously to measure traffic volumes at the diversion point. In addition, drivers were interviewed at a rest stop on I-80 located about two miles downstream of the diversion point.
The vehicle counter/classifier data was collected between noon August 18 and midnight August 22, 1999. Video diversion point data were collected on six days between August 19-29, 1999, during afternoon peak periods when the DMS display was most likely to change from the two-phase message (normal conditions) to the one-phase message (congested conditions). The following results were presented in the report.
A total 135 drivers were surveyed. 37 drivers indicated they had driven through the work zone before, and 98 drivers indicated they saw the DMS.
Twenty-two (22) of the 24 drivers who saw the route diversion message "DELAYS!! PLEASE USE ALT ROUTE" understood it; however, 29 percent thought it was not useful. The primary reasons were:
- It did not state the reason for the delays.
- It did not indicate which alternate route to take.
All 27 drivers who saw the two-phase message "ROAD WORK AHEAD" / "PLEASE USE CAUTION" understood it; however, 23 percent thought it was not useful. The primary reasons were:
- There was no road work at the time.
- The messages did not say which lane was closed ahead.
- The driver already knew about the road work ahead.
The author commented that a disproportionate number of drivers did not notice the two-phase message because drivers were unable to read the entire message (both phrases) twice in seven seconds while traveling at a speed of 75 mi/h.
Author: Maze, T., et al.
Published By: Mid-America Transportation Center, University of Nebraska
Prepared by Iowa State University, The University of Kansas, University of Missouri-Columbia, and the University of Nebraska – Lincoln
Source Date: May 2000URL: http://www.matc.unl.edu/project/articles/nebraska.pdf
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