 The technology that the federal safety regulators are counting on to thwart a massive increase in pedestrian deaths on U.S. roads does not yet work well when it's needed the most. Approximately 76% of pedestrian deaths occur at night, according to the U.S. Department of Transportation. Automatic emergency braking, the technology at the center of the NHTSA rule finalized last week, are often ineffective at night, multiple studies have found.