Seattle-area transportation officials have approved a $5.9-billion, six-lane replacement for the aging State Route 520 floating bridge across Lake Washington. The plan is to go before voters in May. The proposal to replace the Evergreen Point Bridge was selected over an eight-lane, $7.4-billion proposal backed by cities across the lake from Seattle. State highway engineers say the 3,800-ft-long bridge, the world's longest floating structure, built in 1963, is approaching the end of its useful life and is vulnerable to earthquakes and high winds. The new bridge would be built with sufficient capacity to allow a 30-foot expansion at some time in the future to accommodate either light rail or monorail.