VIALOX® NAV® SUPER 4Y® 4Y® stands for 4 Years. With NAV® 4Y® lamps, the relamping interval for groups of sodium lamps in street lighting can be extended to four years. Longer relamping intervals NAV® lamps used to be replaced on a three-year cycle, so just by extending the relamping interval to four years the savings in annual lamp replacement costs amount to 25%. Long-term reduction in premature failures 95% of NAV® 4Y® 150, 250 and 400W lamps are still operational after 16,000 hours. The figure for 50 and 70W lamps is an impressive 92%. This leads to considerable additional savings in replacement costs. More light for longer After 16,000 hours of operation at least 80% of the initial luminous flux is still available.