CITY COUNCIL AGENDA ITEM
ACTION REQUESTED:title
Endorse the Naperville 2050 Road Improvement Plan
body
DEPARTMENT: Transportation, Engineering and Development
SUBMITTED BY: Andrew Hynes, PE, PTOE, City Engineer/Deputy Director
BOARD/COMMISSION REVIEW:
On September 4, 2025, the Transportation Advisory Board unanimously approved the proposed Naperville 2050 Road Improvement Plan. (Vote 7-0)
BACKGROUND:
The City of Naperville maintains approximately 475 centerline miles of streets, including numerous arterial and collector roadways. Traffic flow and congestion on major roads have been a long-standing concern identified through past community surveys. Minimizing congestion on arterial roads and intersections also reduces travel times, lowers emissions, and reduces unnecessary traffic on neighborhood streets.
Between 1988 and 2008, the City of Naperville assessed a road impact fee. Acknowledging that the new development results in additional traffic on the city streets and that capacity improvements were needed to accommodate the additional traffic; the purpose of the fee was to assess developers for the proportionate share of the costs of the improvement of the arterial road system.
A key component of the impact fee process was the development of the Road Improvement Plan. This plan consists of a list of numerous road corridors and intersection capacity improvements needed to meet minimum level of service requirements within a 20-year timeframe accounting for future development and traffic growth. A detailed traffic model was developed to identify capacity deficiencies and recommended improvements. The projects included in the approved Road Improvement Plan were added to the City’s Capital Improvement Plan budget with many implemented over the past 15 years.
Since the impact fee program was discontinued in 2008 and the associated model is approaching the end of its 20-year traffic projection, an updated high-level analysis of current and projected traffic conditions on Naperville’s road network was needed. The updated Road Improvement Plan identifies the location of road and intersection capacity issues and the modifications needed to reach acceptable levels of service (vehicle delay and flow). These improvements will be incorporated into the City’s Capital Improvement Program as new projects to be evaluated in further detail.
DISCUSSION:
2050 Road Improvement Plan (RIP) Update
In May 2024, the City hired Kimley Horn and Associates, Inc. to conduct a study to update the Road Improvement Plan. Over the past year, Kimley Horn worked with staff to collect traffic data, gather public input, perform technical analysis of intersections and corridors on the arterial network, and develop updated road improvement recommendations. Each of these steps is discussed in more detail below.
Data Collection
The initial step of the RIP Update reviewed existing traffic conditions on arterial and collector roadways (as defined in the Master Thoroughfare Plan) and intersections under the City’s jurisdiction. Recent traffic volume data was collected from a variety of sources that included Naperville, DuPage County, and commercially available information. Geometric information related to the current configuration of streets and intersections within the City boundaries was also inventoried.
Intersection and Roadway Segment Capacity Analysis Methodology
The traffic count data, along with geometric road information, was loaded into traffic simulation software to develop an existing conditions model of Naperville major road network. Staff reviewed the analysis results with our consultant to calibrate the model to reflect actual conditions. The model included:
• 162 Intersections
o 104 Signalized Intersections
o 58 Unsignalized Intersections
• 184 Roadway Segments
Intersection Capacity Analysis and Level of Service (LOS)
Using traffic modeling software, intersection capacity analyses were conducted for 162 locations to assess existing operational conditions during the weekday evening peak hour (5 PM to 6 PM). Historically, the Road Improvement Plan evaluation has used the PM peak hour period because travel volumes are typically highest during this time.
The capacity of an intersection quantifies its ability to accommodate traffic volumes and is expressed in terms of level of service (LOS), measured in average delay per vehicle. Levels of service are defined in the Transportation Research Board’s publication of the Highway Capacity Manual (HCM). The level of service standards set forth in the HCM are nationally accepted standards in the traffic engineering profession.
Levels of service are defined from A to F in the manual and are measured by different criteria dependent upon the roadway use, ramps, intersections, expressways, etc. Level of service at intersections is classified by seconds of delay. LOS grades range from A to F, with LOS A as the highest (best traffic flow and least delay), LOS E as saturated or at-capacity conditions, and LOS F as the lowest (oversaturated conditions). The information in Tables 1 and 2 below further defines the definitions and criteria used to determine intersection LOS. The LOS grades quantify and categorize the driver’s discomfort, frustration, fuel consumption, and travel times experienced as a result of intersection control and the resulting traffic queuing.
Road Segment Capacity Analysis
For the purposes of the road segment analysis, 2024 average annual daily traffic volume information provided by the Illinois Department of Transportation was used. To evaluate traffic conditions on arterial and collector roadway segments, level of service was estimated based on a review of the daily traffic volume, roadway classification and roadway characteristics (e.g., number of lanes, divided/undivided, traffic control). The reference for this analysis is the Federal Highway Administration (FHWA) Simplified Highway Capacity Calculation Method for the Highway Performance Monitoring System. Level of service for the roadway links is expressed using an A to F grade similar to intersection capacity analysis.
Existing Traffic Conditions - Capacity Analysis Results
The results of the existing intersection and road segment analysis are illustrated in Exhibit A - Existing Level of Service Map. On this map, intersections are represented as circles and road segments as lines. The color of the circle or line represents the corresponding level of service as defined in the map legend.
Future Conditions - Traffic Growth Projections and Capacity Analysis Results
Year 2050 traffic projections were developed using the Chicago Metropolitan Agency for Planning (CMAP) On to 2050 travel demand model. The 2050 traffic projections for the roadway segments were then compared to existing average annual daily traffic data obtained from IDOT to derive an annual growth rate. For purposes of this analysis, the City was divided into four quadrants along 75th Street and Washington Street. Based on a review of the annual growth rates for each segment, an average annual growth rate was calculated for each quadrant. This methodology was selected to capture variability in the roadway network and land use patterns across the City. A summary of the average annual growth rates is highlighted below.
• Northwest Naperville: 0.84%
• Northeast Naperville: 0.61%
• Southwest Naperville: 1.22%
• Southeast Naperville 0.88%
These annual growth rates were then applied to intersection turning movement volumes in the respective quadrant to develop Year 2050 traffic projections. The resulting traffic volumes were used to evaluate future traffic conditions.
Using the same methodology described for the existing conditions, capacity analysis for the same intersections and road segments were completed for future conditions. The results of the projected 2050 intersection and road segment analysis are illustrated in Exhibit B - Future 2050 Level of Service Map.
Public Involvement
• A public meeting was conducted on January 28, 2025, to gather public input on existing traffic conditions.
• Following the January 28 meeting, an interactive map was posted on the project webpage that allowed the public to post traffic concerns related to specific locations. The interactive map was available for 2+ weeks following the meeting.
Between the meeting and the online map, the public provided nearly 500 comments.
• Additional opportunities for public involvement were provided through the three Transportation Advisory Board presentations in May, August, and September 2025 meetings.
A total of 494 public comments were received. The comments were primarily used to validate analysis locations and concerns. Some comments were related to locations beyond the scope of the RIP update or County or State highways. Staff evaluated those concerns separately or will pass on the comments to these other agencies as appropriate.
Proposed Road Improvement Plan Recommendations
Based on the results of the operational analysis, capacity improvements for arterial and collector roadways under City jurisdiction were identified. If the intersection performed at a level of service D or better, no improvements were considered necessary at that intersection for projected 2050 conditions. If the intersection operated at a level of service E or F, additional lanes were added incrementally to achieve a level of service D.
A planning level feasibility review of each location was also conducted to determine potential right of way and utility conflicts. Considering both capacity and feasibility, a set of recommended intersection and road corridor improvements was developed to improve traffic operations and raise the projected level of service. Exhibits C & D illustrate the locations of recommended intersection and road segment capacity improvements and updated level of service following implementation of the additional facilities.
A summary list of recommended geometric improvements with preliminary construction cost estimates (the Road Improvement Plan Update) is provided in Exhibit E. Note that some intersections involve multiple jurisdictions. In these cases, only the improvements on the City’s approaches are included in the table. The Road Improvement Plan Update consists of 15 intersection improvements, 2 roadway widening projects (119th and 111th Streets), 1 roadway extension (Book Road from 111th Street/Hassert Drive to 119 Street).
Conceptual geometry for each potential improvement is shown in Exhibit F - Concept Level Plans for Proposed Road Improvements.
The RIP evaluation also identified two road segments (portions of 87th Street and Wehrli Road) that have excess capacity. These locations will be further evaluated for potential modifications with the Bicycle and Pedestrian Plan Update.
Transportation Advisory Board Review
• At the May 5, 2025, Transportation Advisory Board meeting (File No 25-0507), Kimley Horn presented a summary of the technical analysis and public comments.
• At the August 7, 2025, Transportation Advisory Board meeting (File No. 25-1009), Kimley Horn presented the proposed intersection and corridor improvements for anticipated 2050 traffic conditions.
• At the September 4, 2025, Transportation Advisory Board Meeting (File No. 25-1185), Kimley Horn presented a summary overview of the proposed plan. The Transportation Advisory Board unanimously approved (7-0) the Naperville 2050 Road Improvement Plan.
A copy of the related portion of the minutes from these three TAB meetings is attached as Exhibit G.
Implementation
With City Council approval of the RIP Update, the implementation schedule for each of the individual projects will be considered through the annual budget process extending over the next 20+ years. Exhibit H includes a matrix of prioritization factors for each project that includes funding, coordination opportunities, available right of way, and several others that will help determine when projects will be recommended to move forward.
As projects move forward to the design process, a more detailed review of project elements such as alternative analysis, right of way needs, utility conflicts, drainage lighting, accessibility, and bicycle and pedestrian accommodations will be conducted. Additional opportunities for public input will also be provided with final consideration by the City Council prior to moving forward to the construction phase.
FISCAL IMPACT:
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