NHTSA’s Report Shows Mixed Results on LEDs
Mar 1, 2013 8:49 AM
The National Highway Traffic Safety Administration’s (NHTSA) technical report reviewing and evaluating LED stop lamps -- “Effectiveness of LED Stop Lamps for Reducing Rear-End Crashes: Analyses of State Crash Data” -- does not support a firm conclusion about whether light-emitting diode (LED) stop lamps and LED center high-mounted stop lamps (CHMSL) are more effective than incandescent lamps.
Previous work on this subject included laboratory experiments that suggest LED lamps were more beneficial than incandescent lamps at preventing rear-impact collisions. NHTSA statistically compared the overall ratio of rear-impact crashes to a control group of frontal impacts before and after the switch to LED.
The main analysis shows a significant overall 3.6% reduction in rear-impact crashes with LED. On the other hand, a non-parametric analysis not only fails to show improvement in significantly more than half the models, but actually shows an increase in rear impacts with LED for 9 of the 17 make-models that switched to LED. It was just the favorable results for high-sales vehicles such as Honda Accord that pulled the overall result into the plus.
Furthermore, and perhaps most important, none of these 17 make-models is a ``clean'' switch pair that shifted to LED without changing anything else. All of the switch pairs shifted to LED at the same time that they changed the rear-lighting configuration and/or redesigned the vehicle. Basically, the crash data probably won't support a firm conclusion until there are more switch pairs, including some ``clean'' switch pairs.
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