A Smart Zone work zone on I-35 near Edgerton, Kansas.
A highway work zone on I-35 near Edgerton, Kansas utilized a "smart zone" work zone that included the use of portable changeable message signs (PCMS), portable speed sensors, portable cameras, and portable variable speed limit signs. Variable speed limits (VSLs) were calculated by a computer program that calculated the 85th percentile speed for each minute of data for each traffic sensor. Each VSL display was associated with 2-3 upstream traffic sensors. The lowest 85th percentile speed of the associated sensors is posted on the work zone VSL sign, rounded up to the nearest 5 mph integer. The posted speed would change every minute if the speed change was a 10 mph difference or every 5 minutes if the calculated speed change was less than 10 mph different than the current display.
Local residents were surveyed about their experience and knowledge of the Smart Zone work zone on I-35. Of the respondents, 92 percent observed or were aware of the variable speed limit signs.
- When asked to rate the usefulness of the variable speed limit signs on a scale of 1 to 7 (1 being not useful, 7 being very useful), 52 percent of respondents found the variable speed limit signs to be very useful.
- 19 percent of respondents found the variable speed limit signs to be useful.
- 29 percent of respondents had negative or neutral feelings about the variable speed limit use in the Smart Zone.