Submitted By
Jack Chalabian, Transportation Commission Chairperson Bill McKenna, Village Engineer
Reviewed By
LKS
Agenda Item Title
Title
A Motion to Concur with the Transportation Commission’s Recommendation to Upgrade the Two-Way STOP Signs to All-Way STOP Signs at the Intersection of Superior Street and Linden Avenue and Direct Staff to Prepare the Necessary Ordinance.
End
Overview
Overview
The Village of Oak Park received a petition to install all-way STOP signs at the intersection of Superior Street and Linden Avenue. The Village conducted crash analysis and traffic studies for the intersection. The Transportation Commission voted four to one to recommend upgrading to all-way STOP signs at the intersection of Superior Street and Linden Avenue at its May 22, 2017 meeting. Staff concurs with the Transportation Commission’s Recommendation.
Body
Staff Recommendation
Approve the Motion
Fiscal Impact
Staff estimates it will cost less than $1,500 to install signage and related pavement markings to upgrade from a two-way to an all-way STOP controlled intersection. There are available funds in the FY2017 General Fund, Public Works - Street Services, account no. 1001-43740-761-550634 for this work.
Background
On October 6, 2016, the Village of Oak Park received a petition to upgrade to all-way STOP signs at the intersection of Superior Street and Linden Avenue. Persons representing 72.1% of the street frontage on the petitioning blocks signed the petition. The petition was certified as a valid petition. See Attachment A for a copy of the petition and the related letter of explanation.
Reasons provided for the petition were: significant amount of non-local traffic using Linden Avenue as a bypass between Lake Street and Chicago Avenue, safety concerns regarding pedestrians traveling east-west on Superior Street (including students of Oak Park River Forest High School and Alcuin Montessori School), vehicles travel at elevated speeds on Linden Avenue, and eliminate driver confusion whether or not this is an all-way STOP intersection (east-west traffic regularly pulls out in front of north-south traffic after stopping). See Attachment B for copies of the written public testimony received by the Village for this item.
Because Chicago Avenue construction continued throughout the fall of 2016, the traffic study data collection was delayed until the spring of 2017. A twenty-four hour traffic volume count and speed study was conducted on Tuesday, April 11, 2017 for the 600 and 638 blocks of Superior Street and 300 and 400 blocks of Linden Avenue. The results were analyzed and then summarized (see Attachment E). During this same study, pedestrian and bicycle counts were also collected. Those results can be found in Attachment F. Staff also reviewed the crash history of the intersection and generated a collision diagram based on the results (see Attachment G).
The petition was reviewed by the Transportation Commission at its May 22, 2017 meeting. Staff gave a presentation on the issue including: background on the petition, history of traffic control devices at the intersection, analysis of the collected traffic data and collision diagram. Area residents provided public testimony on the item. After hearing Staff’s presentation and public testimony, the Transportation Commission deliberated on the item. The draft minutes for the May 22, 2017 Transportation Commission meeting are included as Attachment H.
At the May 22, 2017 meeting, the Transportation Commission voted 4 to 1 in favor of recommending to upgrade the intersection of Superior Street and Linden Avenue from two-way east-west STOP controlled to all-way STOP controlled intersection.
ANALYSIS SECTION
Geometry of the Intersection and Neighborhood Context (Attachments C & D)
The intersection of Superior Street and Linden Avenue (see Attachment C for aerial view) is one block to the north of the Oak Park River Forest High School campus. It is also two blocks east of the Alcuin Montessori School which is located at the southeast corner of Superior Street and Oak Park Avenue.
Attachment D details the traffic control devices on Superior Street between Oak Park Avenue and Ridgeland Avenue as well as the following other east-west streets: Ontario Street, Erie Street and Chicago Avenue.
Traffic Study - Volume and Speed (Attachments E & F)
The average daily traffic on the 600 and 638 blocks of Superior Street was 747 and 682 vehicles, respectively. For Linden Avenue, the average daily traffic was 1,378 vehicles and 1,310 vehicles for the 300 and 400 blocks of Linden Avenue, respectively. Volumes on Superior Street are below the 800 to 1,200 vehicle range for typical daily volumes on residential streets within the Village of Oak Park. While the vehicle volumes on the 300 and 400 blocks of Linden Avenue exceeded the typical daily volumes on residential streets within the Village. The elevated volumes on the 300 and 400 blocks of Linden Avenue are due in part to its proximity to Oak Park River Forest High School and that Linden Avenue is the closest north-south street to the high school that allows travel in both directions from Lake Street to Chicago Avenue. Please see Attachment E for a summary of the vehicle traffic study results as well as the source data.
Regarding vehicular speeds, it is an accepted traffic engineering practice to set the speed limit to the 5 mile per hour increment above or below the 85th percentile speed. Village Staff holds the opinion that the majority of drivers will drive at or near the posted speed limit. In addition, it is an accepted fact that the speed indicated on speedometers can vary up to 2 percent above or below the actual speed of the vehicle.
By definition, the 85th percentile speed is the speed at which 85 percent of the vehicles are traveling at or less than. Conversely, 15 percent of the vehicles will be traveling faster than the 85th percentile speed. It has already been stated that speed limits are typically set to the 5 mile per hour increment above or below the 85th percentile speed. This implies that it is expected that approximately 15 percent of vehicles will be traveling faster than the speed limit, if the speed limit is the 5 mile per hour increment below the 85th percentile speed.
The 85th percentile directional speeds for the 600 and 638 blocks of Superior Street ranged between 23 and 25 miles per hour (mph). The 24-hour survey showed that 15.9% of the vehicles on the 600 block of Superior Street were traveling faster than the posted 25 mph speed limit. For the 638 block of Superior Street, 6.6% of the vehicles were traveling faster than the posted 25 mph speed limit.
The 85th percentile directional speeds for the 300 and 400 blocks of Linden Avenue ranged between 26 mph and 28 mph. The 24-hour survey showed that 31.3% of the northbound vehicles and 32.5% of the southbound vehicles on the 300 block of Linden Avenue were traveling faster than the posted 25 mph speed limit. For the 400 block of Linden Avenue, the percentage of vehicles traveling faster than the posted 25 mph speed limit was 23.2% for northbound traffic and 34.0% for southbound traffic.
Based on the collected data, it appears there may be a speeding issue on the 300 and 400 blocks of Linden Avenue. The Manual on Uniform Traffic Control Devices lists that STOP signs should not be used for speed control. Studies have shown there is little or no effect on vehicle speeds on residential roads after the installation of STOP signs. Vehicle speeds are reduced within 150 feet of the intersection otherwise the effect of STOP signs on vehicle speeds is negligible.
As a result of the petitioners letter of explanation, the Village also conducted a pedestrian and bicycle count for the two hour periods associated with the schools’ arrival and dismissal time periods. Please see Attachment F for a summary of the pedestrian and bicycle study results as well as the source data.
Crash History - Collision Diagram (Attachment G)
Thirty-six months of vehicle crash reports covering the period of May 2014 through April 2017 were reviewed for the Superior Street and Linden Avenue intersection. Please see Attachment G for the collision diagram. The number of reported crashes that occurred at the Superior Street and Linden Avenue intersection for the thirty-six months ended April 30, 2017 totaled zero. The average daily traffic for the intersection as determined as part of this traffic study is 2,073 vehicles. From this data, the 2017 crash rate for the Superior Street and Linden Avenue intersection is calculated to be 0.000 Acc/MEV.
This crash rate is then compared to the critical crash rate for the particular section of the Village’s area-wide traffic study. For the middle north section of the area-wide traffic study (North Boulevard to Augusta Street and Harlem Avenue to Austin Boulevard), the critical crash rate is 0.860 Acc/MEV. If an actual accident rate exceeds the critical crash rate then it is highly probable that the accidents were caused by factors other than chance.
The 2017 crash rate for this intersection is lower than the critical crash for the area as determined in the area-wide traffic study of 1997 (0.860 Acc/MEV). In conclusion, there does not appear to be a problem with vehicle crashes at the Superior Street and Linden Avenue intersection.
Village Staff concurs with the recommendation to approve the petition to upgrade the traffic control devices at the intersection of Superior Street and Linden Avenue from two-way, east-west STOP signs to all-way STOP signs based on 1) the proximity of the intersection to Oak Park River Forest High School, 2) higher than normal volume of traffic on Linden Avenue due in part by trips to and from the high school, 3) significant number of trips at the intersection and in the area are made by student drivers, and 4) to eliminate driver confusion on whether or not the Superior Street and Linden Avenue intersection is an all-way STOP controlled intersection.
Alternatives
Deny the recommendation and the intersection remains two-way east-west STOP-controlled for Superior Street at Linden Avenue.
Previous Board Action
N/A.
Citizen Advisory Commission Action
The Transportation Commission recommended the following:
1. Approve the upgrade from two-way STOP signs to all-way STOP signs at the intersection of Superior Street and Linden Avenue.
Anticipated Future Actions/Commitments
Subject to consensus of the Village Board, staff will submit an Ordinance to the Village of Oak Park Board for adoption for the installation of the north-south STOP signs at the intersection of Superior Street and Linden Avenue at a future Board meeting.
Intergovernmental Cooperation Opportunities
N/A.
Performance Management (MAP) Alignment
N/A.