Official US Government Icon

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure Site Icon

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

The latest general information on the Coronavirus Disease 2019 (COVID-19) is available on the CDC website.

United States Department of Transportation United States Department of Transportation

Railroad Signal Color and Orientation: Effects of Color Blindness and Criteria for Color Vision Field Tests

Document Series
Technical Reports
Federal Railroad Administration
Report Number
Subject Human Factors
Railroad Signals; Signal Color; Signal Orientation; Medical Standards for Color Vision for Locomotive Engineers and Conductors; Color Vision; Color Vision Field Tests; Pseeudoisochromatic Plate Tests; Human Error; Signal Detection Theory

DOT is committed to ensuring that information is available in appropriate alternative formats to meet the requirements of persons who have a disability. If you require an alternative version of files provided on this page, please contact
Last updated: Friday, March 20, 2015