Caltrans and Amtrak began drafting the specification for a third generation of the design in 2006. This specification, dubbed "Corridor Car for the 21st Century" or C21, became the basis for the design work undertaken by the Next Generation Corridor Equipment Pool Committee (NGCE) under the provisions of the Passenger Rail Investment and Improvement Act of 2008 beginning in 2009. Caltrans and the Illinois Department of Transportation ordered 130 of these Next Generation Bi-Level Passenger Rail Cars from Sumitomo (with Nippon Sharyo as the builder) in 2012. In August 2015, a new car shell failed a buff strength compression test. Increasing the buff strength would require a complete redesign of the car, and would delay delivery beyond the expiration of a $220 million American Recovery and Reinvestment Act of 2009 (ARRA) grant that funded the order. In November 2017, Sumitomo cancelled their order of bilevel cars with Nippon Sharyo, and instead contracted with Siemens Mobility to build 137 single-level Viaggo Comfort cars instead of the bilevel cars.