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 not impacted by a School Walk Route and Lucent Ln and Snapper Rd do not meet warrants for an adjustment. Both received 0%.
3. Crashes - Neither street has a crash history that would warrant a reduction. Both received 0%.
4. Parking - Lucent Ln has sufficient width for on -street parking, Snapper Rd does not have sufficient width for on-street parking where parking indents are not present. Lucent received 10%, Snapper received 0%.
Taking all the allowable reductions, the adjusted prevailing speed is calculated to be 19.8 mph for Lucent Ln and 19.8 mph for Snapper Rd. The adjusted prevailing speed is set to the nearest allowable 5 mph increment, which establishes 25 mph as the lowest possible speed in accordance to the City of Naperville Neighborhood Residential Speed Limit Policy, the IDOT manual, and the Illinois Vehicle Code. The speed study worksheets illustrating the allowable reductions are located in the attachments.
The study warrants establishing a 25-mph speed limit for the following streets:
|
No. |
Street |
Area of Restriction |
|
1 |
Bright Hawk St |
Wetherbee Ln to Wrenson Ave |
|
2 |
Hattie St |
Weatherbee Ln to Wrenson Ave |
|
3 |
Hibbard Rd |
Weatherbee Ln to Lucent Ln |
|
4 |
Josiah Rd |
Lucent Ln to Weatherbee Ln |
|
5 |
Lucent Ln |
Weatherbee Ln to Warrenville Rd |
|
6 |
Snapper Rd |
Lucent Ln to Weatherbee Ln |
|
7 |
Weatherbee Ln |
Terminus/Hibbard Rd (west) to Naperville Rd |
|
8 |
Wrenson Ave |
Lucent Ln to Weatherbee Ln |