The California Air Resource Board (CARB) is the organization that makes it more complicated, but more environmentally friendly, to manufacture cars for the USA. If automakers chose to simply ignore CARB, their cars would not be legal for sale in the most populous state in the union, so they have to engineer the vehicles to two sets of standards.
CARB also looks into technologies that will help automakers reach its standards, and to that end it partnered with Lotus Engineering to see what can be done to reduce the weight of vehicles using a porky Toyota Venza as a Guinea pig.
What lotus has done is create a "lightweight and commercially viable" body structure that reduces the weight of the Venza by 31%. Safety was a factor, as the vehicle will still meet all safety standards and even has greater chassis-rigidity.