Over 4,500 people are killed each year in the USA in road collisions that involve semi tractor-trailers and other large trucks, and the majority of those killed are in smaller vehicles which, for whatever reason, are simply too close to the truck concerned.
Daytime Running Lights [DRL] commonly only illuminate the front lights of a vehicle, and not the rear lights. (See the photograph below.)
Usually, they also do not illuminate the dashboard lights for the speedometer and other instruments and controls. This is intended to alert drivers to the fact that only the DRLs are operating and therefore only the front lights are on, but as most drivers have never been adequately informed about this scenario, many just assume that there is a fault with the dashboard lights and drive on, unaware of the danger they are causing for themselves and others.