TRANSPORTATION ADVISORY BOARD AGENDA ITEM
ACTION REQUESTED:
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Approve a recommendation to establish a 25 MPH speed limit for the Naper Commons subdivision (Item 1 of 3)
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DEPARTMENT: Transportation, Engineering and Development
SUBMITTED BY: Sydney Smith, Transportation Project Manager
BACKGROUND:
When subdivisions approach build-out and the streets have been turned to the City for maintenance, staff evaluates the area to establish speed limits and basic right of way controls. Naper Commons had their roads finished and build out completed in late June 2025.
Naper Commons is a newer subdivision bordered by the Danada Forest Preserve (north and west), Naperville Rd (east), and Warrenville Rd (south).
DISCUSSION:
Traffic data was collected at three locations across the Naper Commins subdivision, this included two locations that were chosen for establishing the speed limit. Those two studies were done at Lucent Ln and Snapper Rd. All studies were conducted in July 2025.
The study warrants used to establish speed limits are located in Section B of the Illinois Department of Transportation (IDOT) "Policy on Establishing and Posting Speed Limits" and Chapter 11, Article VI of the Illinois Vehicle Code. The 85th percentile speed on Lucent Ln was 23.5 mph and the upper 10 mph pace range average was 26 mph. The prevailing speed is the average of the 85th percentile speed and upper 10 mph pace, which equates to 24.75 mph. The measured 85th percentile speed for Snapper Rd is 22 mph and the upper 10 mph pace range average was 22 mph. The prevailing speed is 22 mph.
Section B of the IDOT manual allows for adjustments when altering a speed limit due to road factors. Those factors/conflicts include the presence and/or number of driveways, pedestrians, crashes, and parking. The following are the allowable conflict reductions:
1. Driveways - Lucent Ln and Snapper Rd meet warrants for adjustments on driveways. Both received 10%.
2. Pedestrians - Naper Commons is...
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