The original source has slightly more information: https://www.transportation.gov/fastlane/fonts-and-highway-safety https://www.transportation.gov/fastlane/font

The original source has slightly more information: https://www.transportation.gov/fastlane/fonts-and-highway-safety https://www.transportation.gov/fastlane/fonts-and-highway-sa... “After more than a decade of analysis, we learned that retro-reflective sign sheeting materials that direct a vehicle’s headlamp beams back to the observer were the primary determining factor in improved nighttime visibility and legibility.”