The HD Sierra and its twin the Chevrolet Silverado HD are designed for heavy towing and hauling. The 6.0-liter V8 and 6.6-liter turbodiesel, both mated to a six-speed automatic, carried over on the 2015 redesign. There is also a natural gas (CNG) version of the 6.0-liter V8. GM said that the new cabs and interiors provide increased space and comfort, with extensive storage space. The Sierra 3500HD is available with head-curtain and seat-mounted side airbags. Braking and handling capabilities on the outgoing HD Sierra come close to those of the Sierra 1500. Handling is not agile but has a modicum of responsiveness that other three-quarter-ton trucks don't provide, but it rides more stiffly than the Sierra 1500. Beginning with the 2016 model year, Apple CarPlay and Android Auto capabilities are added to the infotainment system.