traction control, anti-lock brakes, brake assist, and electronic brakeforce distribution are also standard. For the 2010 model year, a driver and front passenger knee airbag becomes standard. Toyota's Tundra was the first full-size pickup to have earned the IIHS's Top Safety Pick accolade, followed by the redesigned 2009 Ford F-150. In tests conducted by the IIHS, the Tundra received an overall "Good" score in the frontal offset crash test, the highest possible rating in the side impact crash test, and the maximum score for rear crash protection. The primary difference between IIHS and NHTSA frontal crash testing is the IIHS conducts an offset test where a smaller portion of the vehicle's structure absorbs the energy of the crash. This type of crash test is more demanding on the vehicle's structure, while the full-frontal crash test is more demanding on the vehicle's restraint systems. Both IIHS and NHTSA frontal-impact tests can only be compared among vehicles of similar weights. Because the Tundra's Vehicle Stability Control system is disabled when the vehicle's 4x4 system is engaged Consumer Reports has questioned the Tundra's Top Safety Pick award. Toyota's response is the Tundra does not feature a center differential which would become a weak point in the drivetrain. However the stability control system remains operational at times when the truck is in 4x2 mode though many drivers will select the 4x4 mode in slippery conditions. As of the 2010 model year, this has been corrected. Electronic stability control functions in 4x4hi and is disengaged in 4x4lo. This is verified by the updated owner's manual, visor instructions, and road tests in snow and ice in 4x4hi. When understeer or oversteer occurs in 4x4hi a beeping noise is emitted, and the dash indicator lights up yellow indicating that VSC is activated, braking individual wheels to match driver input at the steering wheel. TRD supercharger Toyota began selling a bolt-on TRD supercharger kit for the 5.7 L V8 Tundra during June 2008. Power output is increased to and of torque. When the installation is carried out by a Toyota dealership the existing warranty remains intact. This kit features Eaton's TVS Roots-type supercharger which utilizes twin four-lobe rotors, a design shared with the newly introduced Toyota TRD Aurion, Chevrolet Corvette ZR1 and Cadillac CTS-V. TRD discontinued the TRD Supercharger in mid 2015, meaning that the 2015 model year is the last year that has an official TRD ECU