Chicago Department of Transportation Traffic Signal Planning Audit

The Office of Inspector General (OIG) conducted an audit of the Chicago Department of Transportation’s (CDOT) traffic signal planning practices. Traffic signals are one of the most cost-effective tools for promoting traffic safety, reducing congestion, and minimizing air pollution. CDOT is responsible for managing 2,834 signalized intersections across Chicago. The objective of the audit was to determine whether CDOT’s traffic signal planning meets industry best practices as defined by the Federal Highway Administration (FHWA). FHWA recommends that agencies have a documented traffic signal management plan with defined goals, objectives, and performance measures. The plan should also describe staff’s responsibilities and explain how they support the program’s goals and objectives. FHWA provides recommended staffing levels based on the number of traffic signals an agency manages.

OIG concluded that CDOT does not have a traffic signal management plan, nor does it have objectives or performance measures connecting its traffic signal management program to broader Department goals and City plans, such as the Roadmap for the Future of Transportation and Mobility in Chicago, Vision Zero, and Chicago Streets for Cycling Plan 2020. Without a signal management plan, CDOT cannot ensure that traffic signals are optimized to promote traffic safety, reduce congestion, and minimize air pollution.

OIG found that CDOT’s traffic signal planning practices do not align with FHWA guidance, which recommends having a traffic signal management plan that sets goals and objectives, defines performance measures, and delineates staff responsibilities. While CDOT seeks opportunities to upgrade signals when possible, its lack of an overall plan prevents the Department from prioritizing signal improvements to meet broader goals and maximize its limited resources.

In addition, OIG found that rather than proactively maintaining and retiming traffic signals, CDOT conducts most of its work in response to 311 complaints, aldermanic requests, and major construction projects. This approach to maintenance limits CDOT’s ability to address problems before they become hazardous or unnecessarily expensive to repair. And the Department’s reactive approach to traffic signal retiming means that over time, due to shifting traffic patterns and timing drift, signals may not be optimally programmed to handle traffic. FHWA suggests that adopting a traffic signal management plan helps agencies strategically shift from reactive to proactive work, ultimately improving efficiency. Under its current practices, CDOT may be missing out on a cost-effective opportunity to improve the flow of motor vehicles, bicycles, and pedestrians, decrease fuel consumption and corresponding emissions, and improve safety by reducing crash rates. CDOT management stated that the Department does not have enough staff to proactively retime and maintain traffic signals. Our review confirmed that the Department’s number of traffic signal engineers and technicians falls well short of the FHWA recommended staffing levels. However, the Department does use contractors to supplement its staff.

OIG recommends that CDOT develop a traffic signal management plan aligned with FHWA recommendations. This plan should include clear goals and objectives, performance measures, and a strategy to transition toward more proactive traffic signal maintenance and retiming work. We also recommend that CDOT conduct an analysis to determine its staffing needs related to traffic signals, and then work with the Office of Budget and Management to meet those needs.

In response to our audit findings and recommendations, CDOT stated that it will develop a Traffic Signal Management Plan (TSMP) using FHWA guidance as a framework. The TSMP will be developed and implemented by the Divisions of Engineering, Traffic Safety, and Electrical Operations, as well as the Commissioner’s Office. The Department stated that the TSMP will include goals tied to CDOT’s strategic plans along with objectives and performance metrics to measure progress towards the goals. The TSMP will also specify staff members’ roles and responsibilities related to achieving the goals.

In response to our audit findings and recommendations, CDOT stated that it will develop a Traffic Signal Management Plan (TSMP) using FHWA guidance as a framework. The TSMP will be developed and implemented by the Divisions of Engineering, Traffic Safety, and Electrical Operations, as well as the Commissioner’s Office. The Department stated that the TSMP will include goals tied to CDOT’s strategic plans along with objectives and performance metrics to measure progress towards the goals. The TSMP will also specify staff members’ roles and responsibilities related to achieving the goals.

The Department will utilize the TSMP as a framework to prioritize improvements and maintenance for the City’s 2,834 signalized intersections.

Finally, the Department stated that it will analyze its traffic signal staffing levels, compare them to FHWA guidance, and work with the Office of Budget Management to better meet CDOT’s staffing needs.