This from a 2000 NHTSA report on driving distractions:
Driving Distractions NHTSA Report
"Surprisingly, large numbers of comments posted in these areas addressed the use of Daytime Running Lamps (DRLs). Nearly all were negative comments relating to the practice. DRLs were perceived to needlessly draw attention away from the road, reduce the conspicuity of emergency vehicles and motorcycles, contribute to glare and driver fatigue, and cause other drivers to adapt their behavior in manners that may not be safe. The main concern appeared to be with the use of excessively bright lights. Calls for limits in brightness as well as research to document the effect of DRLs on crashes and the visibility of emergency vehicles were made by many participants."
Michael