Evaluation of after-market light emitting diode headlight bulbs

Taking advantage of growing consumer interest in light emitting diode (LED) headlights, an increasing number of after-market LED replacement bulbs is available on the market. They are designed to have similar socket shapes and sizes as halogen bulbs, in order to fit into existing headlight housings. Although none of these LED replacement bulbs conform to present federal headlighting regulations, and some are labeled for "off road use" only, others claim to meet current regulations. Regardless, many different LED bulbs can be easily purchased and installed by vehicle owners, who may or may not be aware of their regulatory status. Several different LED replacement bulb kits, each designed to replace a conventional 55-W H11 halogen bulb, were purchased and tested in three different low-beam headlight units. Photometric measurements at several critical test points for headlight performance revealed that none of the resulting distributions met all of the test point photometric requirements. Some intensity values were lower than allowed minima while others exceeded allowed maxima. Photographs of the resulting beam patterns for each combination of LED bulb and headlight unit, when compared to the patterns with the halogen bulb, revealed stark differences in performance between the halogen and LED bulbs. Even though some bulbs more closely matched halogen performance, performance for different headlights using the same LED bulb could vary widely. These findings suggest that using after-market LEDs to replace halogen bulbs can compromise headlighting performance.