Researchers Assessed the Safety Effects of Upgrading the Roadway Lighting System in Tampa, FL Using an Automated Diagnosis Tool and Real-World Street Lighting Data.
Tampa, Florida, United States
Development of Automated Roadway Lighting Diagnosis Tools for Nighttime Traffic Safety Improvement, Phase II
Summary Information
Adequate roadway lighting ensures nighttime safety and security for multimodal road users. A previous CTEDD-study (Development of Automated Roadway Lighting Diagnosis Tools for Nighttime Traffic Safety Improvement, Phase I) developed and improved an analysis tool to diagnose lighting patterns and estimate nighttime crash risks based on big lighting data. This study built upon Phase I, investigating the impacts of lighting patterns on nighttime pedestrian crashes and the effectiveness of LED technologies. This study also developed an algorithm for uniformity diagnosis and applied enhancements to the analysis engine to improve its functions and processing speed. Illuminance measurements for more than 300 center miles in Tampa, Florida from 2011 to 2014 were used in this study, as well as street lighting data from 440 roadway corridors in urban and/or suburban areas. The study also collected a 2018 inventory of LED light poles on major corridors in the Tampa Bay area from FDOT District Seven.
METHODOLOGY
The study used the matched case-control method (each case is paired with a control based on matching characteristics) to investigate the impacts of lighting patterns on nighttime pedestrian crashes. Crash Modification Factors (CMFs) for horizontal illuminance's mean and standard deviation were used to assess average lighting levels and uniformity, respectively. Additionally, the study formulated a Safety Performance Function (SPF) for LED technologies using data from the Florida Department of Transportation (FDOT) District Seven's light pole inventory, detailing the location and type (traditional High Pressure Sodium (HPS), LED, or unknown) for each lighting pole. A cross-sectional data analysis approach was used to compare nighttime crash frequencies between two site groups (with and without LEDs) during the same time frame of 2018 to 2019.
FINDINGS
- The CMF for LED was obtained as 0.83, indicating that upgrading the lighting system on a roadway segment from HPS to LED is likely to reduce nighttime crash frequency by 17 percent.
- Assuming an annual usage of 4,000 hours, LEDs are estimated to have an estimated average lifetime of over 10 years, compared to about 5.5 years for traditional metal halide lamps, resulting in an 81.8 percent improvement in usable lifetime.
- These results suggest that LEDs offer not only economic advantages, such as a longer service life, but also safety benefits.
