Carolina. Researchers at the Advanced Power and Energy Program at the University of California, Irvine, and the Institute of Transportation Studies at the University of California, Berkeley, began testing two specially made Priuses and analyzing driver behavior, study air quality and energy use. Model year changes In late 2005 (for the 2006 model year), Toyota introduced some minor cosmetic changes for the XW20, such as a slightly updated front-end, revised instruments, and repositioned rear seats. Other changes comprised a higher-resolution liquid crystal display, as well as new optional features such as a backup camera, advanced air bags and an upgraded audio system with an auxiliary input. In 2006 (2007 US model year) the Prius added side-curtain air bags (standard on all models). A Touring Edition was introduced, with an elongated and larger rear spoiler as well as larger, sharper-pointed, seven-spoke, 16", magnesium wheels with plastic hubcap covers to protect them from scratches when parking against the curb. The Touring Edition also comes with a firmer, European-style, tuned suspension, standard high-intensity-discharge (HID) headlights, and integrated (non-HID) fog lights. In 2005, Toyota had to fix a software glitch that caused the Prius' engine to enter "limp" mode with electric-only operation, following 68 stall complaints in the U.S. out of 160,000 worldwide sales. In June 2006, Toyota also recalled about 170,000 Prius models from 2004 to 2006 due to a faulty intermediate shaft and sliding yoke in the power steering system. Safety A 2011 Los Angeles Times article stated that complaints about sudden acceleration and rollover from 2006 to 2009 models have led to recalls. On another matter, an NHTSA database shows that 49% of all customer complaints about these model years were related to lighting, headlamps or visibility. Out of 216,000 Priuses with the optional high intensity discharge (HID) headlamps, there were 28,000 warranty repairs of this system. The headlamps would sometimes shut off without warning, and in rare cases, both headlamps would shut off. There were some injuries but no fatalities. Toyota avoided a recall on the headlights by agreeing to a class action settlement in which the warranty period was extended from three years to five years and by agreeing to reimburse owners for previous repairs. There was some remaining controversy over whether the failures were caused by the bulbs themselves or the computer system controlling them. US National Highway Traffic Safety Administration (NHTSA) crash testing of the 2004 US