Crews installing new underground utility lines beneath Tropicana Avenue will cause traffic delays beginning Monday through September, the Clark County Department of Aviation says. The utility improvements are necessary to provide better electrical service from NV Energy substations to McCarran International Airport's $2.4 billion Terminal 3 project, which is scheduled to open in mid 2012, says Chris Jones, a spokesman for the aviation department. Affected areas are located within a 1.6-mile stretch of Tropicana from east of Interstate 15 to Paradise Road.