Zone 13 Post-Study Links Zone 13 Study Return to Neighborhood Traffic Study Main Page

• Purpose
   
• Summary
   
• Traffic Volume Data
   
• Traffic Speed Data
   
• Accident Data
   
• Conclusion
   
• Resident Letter
   
• Key People
   
• Contact Us

The purpose of the first post-study is to evaluate how the neighborhood streets are operating since making both intersection traffic control and speed limit modifications in January 2007. This is done by collecting vehicular volume and speed data through the use of mechanical traffic counters and receiving accident reports from the Police Department. The data is then analyzed to verify traffic is flowing efficiently and safely in the neighborhood. It is also analyzed to determine any locations that have experienced a noticeable increase in daily volume and/or average speed. These locations will then be further examined as part of a second post-study.

The first post-study will be performed approximately 6 months after making the sign changes. Unless a significant issue is evident after reviewing the data, no further sign changes will be made during this initial review. During this time period, many motorists are still becoming accustomed to the changes and the results may not be indicative of future traffic conditions. For this reason, a second post-study will be performed approximately 12 months after making the sign changes. Once a second post-study is completed, a Neighborhood Meeting will be held to provide an opportunity for residents in the neighborhood to share their thoughts with the Village. The Village Board of Trustees will then decide whether any further sign changes should be made in the neighborhood.

Based on the collected data from the first post-study, no sign changes are recommended at this time in the neighborhood. The first post-study involved gathering vehicular volume and speed data at 22 locations, monitoring pedestrian activity at 2 intersections, and reviewing accident records at all 28 intersections in the neighborhood. Below is a summary of the results:

Daily Volume -
      Stayed consistent or decreased at 18 locations (82%)
      Increased by 10% or more at 4 locations (18%)

Average Speed -
      Stayed consistent or decreased at 22 locations (100%)
      Increased by 5mph or more at 0 locations (0%)

Accident Rate (# accidents per month in the neighborhood) -
      Before the sign changes: 0.58
      Since the sign changes: 0.00

Traffic volumes fluctuate on a daily basis and, as such, any increase or decrease in traffic is not necessarily attributed to the intersection traffic control and speed limit modifications. Traffic volumes typically vary by month of the year, day of the week and time of the day. And a ten to fifteen percent variation in traffic volumes is typical in suburban areas.

Any location that experiences an increase in traffic volume of ten percent or more will be reexamined as part of the second post-study. The ten percent increase was selected as it represents the lower threshold of the ten to fifteen percent variation in traffic volumes that is typical in suburban areas. It should not be interpreted as the threshold that signifies a concern. Many factors affect traffic volumes including those discussed above as well as roadway classification (collector vs. local) and nearby land use (residential, commercial, schools, etc.).

Of the 22 locations where traffic volume data was collected, daily volumes decreased at 16 locations and increased at 6 locations. A comparison of the daily volumes before and after the sign changes indicates that as a whole traffic volume has remained relatively stable. Of the 6 locations that experienced an increase in traffic volume, 4 locations saw a ten percent or more increase. The table below highlights those streets that have experienced an increase in traffic volume of ten percent or more and will be reexamined as part of a second post-study.

* may be the result of a unique occurrence as the sign changes brought a greater level of
   traffic control

Daily Traffic Volume Map

Similar to traffic volumes, traffic speeds also will vary by season or month of the year, day of the week and time of the day. As such, any increase or decrease in traffic speeds is not necessarily attributed to the speed limit and intersection traffic control modifications.

Any location that experiences an average speed of 30 mph or greater and/or an increase in average speed of 5 mph or more will be reexamined as part of the second post-study. The 30 mph average speed was selected as it represents a 5 mph increase over the 25 mph posted speed limit in the neighborhood and is higher than the average speed seen on most neighborhood streets. Furthermore, the increase in average speed up to 5 mph was selected as an acceptable range because of the expected variability in speeds. Average speeds exceeding the criteria should not be interpreted as the threshold that signifies a concern. Many factors affect traffic speeds including those discussed above as well as weather and the roadway’s physical characteristics such as width, number of travel lanes, hills, curves and condition.

Of the 22 locations where traffic speed data was collected, average speeds were below the limits described above at all 22 locations. A comparison of the average speeds before and after the sign changes indicate that as a whole traffic speed has remained stable.

To view the average traffic speeds on all streets included in the first post-study, click on the link below.

Average Traffic Speed Map

At the time of the first post-study, 6 months had passed since implementation of the intersection traffic control and speed limit modifications. No accidents had occurred at the 28 intersections in the neighborhood during this time period. The accident data indicates that the consistent set of traffic regulations have created a more orderly flow of traffic and enhanced safety. Nevertheless, accident records for the entire neighborhood will be reexamined as part of a second post-study. The table below summarizes the accident data.
 

The results of the first post-study indicate that the operating characteristics within the neighborhood have generally improved since implementation of the intersection traffic control and speed limit modifications. Thus far, it appears the sign changes have improved the flow of traffic within the neighborhood and enhanced safety. Overall, traffic volumes and speeds are within acceptable ranges and the accident rate has decreased. While some streets have experienced an increase in traffic volume and/or speed, the number of such locations has been very limited. These locations will be given further attention as part of a second post-study that will take place approximately 12 months after the sign changes. The second post-study will again evaluate traffic volume, traffic speed and accident records.

Key People

Below is contact information for key people involved in this study: