On the eve of “Carmageddon II,” researchers from the University of California, Los Angeles revealed that last year’s July 15-17 closure of Interstate 405 resulted in significant air quality improvements in the vicinity of the freeway. The study’s findings, announced September 28, show that concentrations of ultrafine particles (air pollutants with a diameter of less than 0.1 microns) dropped by 83 percent within minutes around the closed 10-mile stretch of the 405, according to a UCLA press release. Concentrations of larger PM2.5 particles dropped 36 percent. The researchers also found that with an overall decrease in traffic across the Los Angeles area during the Carmageddon weekend, “air quality … improved 75 percent in parts of West Los Angeles and Santa Monica and an average of 25 percent regionally — from Ventura to Yucaipa, and Long Beach to Santa Clarita.” Yet the air quality improvements disappeared with the return of heavier traffic the next week. UCLA Researcher’s plan on studying Carmegeddon II’s effects on air quality once the road project begins. The 405 interstate highway is scheduled to close for two days this past weekend.