The present experiment investigated the effect of small amber lamps mounted near the front and rear on each side of a passenger car-so called side marker lamps-on visual detection and recognition of passenger cars in complex nighttime environments. It was determined whether cars equipped with side marker lamps are detected and recognized earlier and more accurately than cars without side marker lamps. Subjects were presented with slides of natural nighttime scenes in which a car, either with or without side marker lamps, viewed from its side, approaching from a side street, was either present or not. Subjects determined as fast as possible whether a car was present or not. Reaction time measures (speed and accuracy) indicated that both under clear and fog visibility conditions, a car equipped with side marker lamps was detected and recognized earlier and more accurately than a car without side marker lamps. The results indicate that side marker lamps increase both lateral conspicuity and recognizability suggesting that side marker lamps may be effective in reducing the number of nighttime angle collisions.