Nationwide, United States
A Methodology and Case Study: Evaluating the Benefits and Costs of Implementing Automated Traffic Signal Performance
Summary Information
This study introduced a flexible method to evaluate performance-based traffic signal operations and maintenance. The intent was to describe advantages and disadvantages of using a proactive, performance-based traffic signal monitoring process, executed through the Automated Traffic Signal Performance Measures (ATSPM) Program as compared to a traditional reactive approach for monitoring and retiming traffic signals. The following agencies that adopted and incorporated the ATSPM approach were interviewed and participated in the study.
- Utah DOT (UDOT)
- Georgia DOT (GDOT)
- Pennsylvania DOT (PennDOT) with personnel from Cranberry Township, PA
- Lake County, Illinois DOT (LCDOT)
- Clark County, Washington
- Maricopa County DOT (MCDOT).
METHODOLOGY
The methodology included 16 potential cost items and 12 benefit items that were considered by analysts. Each item was defined and a basic formula was used calculate model inputs. An example application for a hypothetical deployment was illustrated using this benefit-to-cost analysis methodology. Benefit items were estimated based on reductions in time needed for tasks reduced through ATSPM and potential benefits to the public from improved signal timing resulting in increased safety or reduced delays.
Potential benefits of ATSPMs identified by the study included:
- Avoidance of manual data collection
- Avoidance of unneeded retiming/maintenance activities
- Reduced public complaint response time
- Value of performance documentation
- Discovery and repair of failed detectors
- Discovery and repair of broken communication
- Discovery and resolution of inefficient green distribution
- Discovery and improvement of poor coordination
- Discovery and mitigation of pedestrian operational issues
- Discovery and resolution of preemption-related issues
- Identification of locations with potential safety issues.
The methodology introduced in this study was applied to six case studies that were early adopters of the ATSPM, including Georgia Department of Transportation (GDOT), Utah Department of Transportation (UDOT), Cranberry Township, PA, Maricopa County Department of Transportation (MCDOT), Lake County Department of Transportation (LCDOT), and Clark County, WA. Table 1 provided an overview of important operational characteristics of the agencies.
Table 1: Operational Characteristics of the Agencies in the Six Case Studies
|
Agency |
Number of Signals |
Number of Signal Operations Staff |
Use of ATSPM |
|
GDOT |
6804 signals. |
70–80 full-time employees, including consultants. |
Continuous. |
|
UDOT |
1,252 traffic signals and 19 High-Intensity Activated crossWalK beacon (HAWK) signals owned and operated by UDOT. |
18 staff and 3 signal timing consultant firms. |
Continuous. |
|
Cranberry Township |
49 signals. |
Four engineers and one technician. |
In early deployment. |
|
MCDOT |
170 (117 monitored with ATSPM) operated by MCDOT |
2 full-time employees and 4 on-call consultants. |
Automated alerts; as needed. |
|
LCDOT |
180 signals; 133 signals under ATSPM, the rest will be under ATSPM by the end of 2019. |
1.5 full-time employees, excluding sporadic engagement consultants. |
On a daily basis. |
|
Clark County |
98 traffic signals, 3 HAWK signal, and 24 signals for other agencies. |
Nine staff and consultants. |
As needed (now); continual (future). |
FINDINGS
The quantified benefits of the six case studies using ATSPM were estimated using a 10-year life cycle and a discount rate of five percent.
- ATSPM adopted by GDOT estimated savings of $4,632,000 due to manual data collection avoided, and $4,863,600 due to complaint response time reduction; a total savings of $9,495,600.
- ATSPM adopted by UDOT estimated savings of $20,690,094 due to manual data collection avoided, $6,225,408 due to complaint response time reduction, $57,900,000 due to quicker response to failed detection, $23,160,000 due to signalized intersection capacity and progression benefits; a total savings of $107,975,502.
- ATSPM adopted by Cranberry Township, PA, estimated savings of $382,140 due to manual data collection avoided, $1,023,672 due to scheduled maintenance avoided, $260,936 due to complaint response time reduction; for a total savings of $1,666,748.
- ATSPM adopted by MCDOT estimated savings of $176,016 due to manual data collection avoided, $866,184 due to scheduled maintenance avoided, $441,584 due to complaint response time reduction; for a total savings of $1,483,784.
- ATSPM adopted by LCDOT estimated savings of $3,612,960 due to manual data collection avoided, and $440,781 due to complaint response time reduction; for a total savings of $4,053,741.
