Saturn S series Twin Cam cylinder head had now featured a new roller-rocker setup with hydraulic tappets and roller cams replacing the conventional bucket lifter setup of the previous engine in the S series. Also introduced for the 1999 model year S-series vehicles that were sold in California was a different type of an exhaust manifold that housed an upstream catalytic converter (this converter had heated up much faster than the conventional unit, and it had also decreased exhaust emissions faster as well), and it also had provisions for an air-injection reaction system (This had injected fresh air into the exhaust to reduce
Alternatives to car use (petroleum-powered) car and contribute to transport sustainability. They also provide other significant benefits such as reduced traffic-related injuries and fatalities, reduced space requirements, both for parking and driving, reduced resource usage and pollution related to both production and driving, increased social inclusion, increased economic and social equity, and more livable streets and cities. Some alternative modes of transportation, especially cycling, also provide regular, low-impact exercise, tailored to the needs of human bodies. Public transport is also linked to increased exercise, because they are combined in a multi-modal transport chain that includes walking or cycling. According to the MIT Future Car