dual under-seat subwoofers and an amplifier was standard equipment, with a thirteen-speaker Harman Kardon "Logic 7" premium surround sound audio system available as an option on all models. An emergency hotline feature (BMW Assist) was also available for the E60. The BMW Assist system could also use the phone network to notify the driver and their preferred BMW dealership when servicing was due. This feature was standard on all E60 models sold in the United States. Other features available in the E60 initially included active cruise control, Bi-Xenon headlights, run-flat tyres, active anti-roll bars, head-up display and active steering. Safety-related items include Dynamic Stability Control (DSC), adaptive headlights and night vision. In 2009, the iDrive system was upgraded from the first-generation "CCC" interface to the newer "CIC" interface. The audio system control panel added six multifunction preset buttons that could be programmed to store favorite radio stations and frequently-dialed telephone numbers for the Bluetooth hands-free system. The iDrive controller in the center console was also redesigned, and now integrated shortcut keys for frequently-used functions. Over the E60's lifespan, the following features were added: Active Cruise Control with Stop & Go, keyless entry ("comfort access"), LED taillights, Lane Departure Warning and Brake Force Display. The E60 was the first 5 Series in 22 years where the centre console was not angled towards the driver, however the E60's successor returned to angling the centre console towards the driver. In 2003 a 6-speed SMG-II gearbox was offered as an option on the 525i, 530i, 545i and 550i in some markets. Engines Petrol At launch, the E60 used the previous generation E39 5 Series' M54 straight 6 engine in the 520i, 525i and 530i models. The only petrol model with a new engine at launch was the 545i with the N62 V8. The M54 was phased out after the 2005 model years and replaced with the straight-4 N43 (in the 520i) and the straight-6 N52 engine (in the 525i and 530i). The model range was also expanded the same year to include a wider range of models like the 523i, 540i and 550i. In 2007, the only turbocharged E60 model was introduced, the 535i with the twin-turbo straight-6 N54 engine. This model was exclusive to the North American market and was not sold in Europe. Diesel The only diesel model available at launch was the 530d, which used an updated "TU" version of the