According to the FHWA/ITE Toolbox of Countermeasures, published in August 2008, adding retroreflective sheeting to traffic signal backplates can reduce all crashes as much as 15%.
The point: Many countermeasures beneficial to color-deficient drivers are also of benefit to ALL drivers.
The Toolbox of Countermeasures for intersections can be found here: http://tinyurl.com/dhmtyq
An abstract of the referenced study, a TRB paper and presentation from Canada, is here:
