plug-in hybrids is (83.3 km/L). However, a leading Opel engineer prefers saying 169 Wh/km (16.9 kWh/100 km) while battery-powered, and then 20 km/L (5 L/100 km) petrol-powered. The ECE R101 standard weights charge-depleting mode as 76% and gasoline-only driving as 24%. Operating cost and payback period According to Consumer Reports in December 2011, the Chevrolet Volt fuel cost in electric mode was 3.8¢/mile. According to Edmunds.com, the price premium paid for the Volt in 2012, after discounting the U.S. federal tax credit, takes a long time for consumers to recover in fuel savings, often longer than the normal ownership time period. Tailpipe emissions Safety The Volt received a five-star overall crash safety rating from the National Highway Traffic Safety Administration (NHTSA), the highest possible score. This rating was obtained with NHTSA's New Car Assessment Program for 2011 model year vehicles. Accident and rescue handling In August 2010, General Motors began a training program for first responders when performing rescue duties involving the Chevrolet Volt. Warning sounds Due to significant noise reduction typical of vehicles traveling in all-electric mode at low speeds, the Volt is fitted with a manually activated electronic warning sound system called Pedestrian-Friendly Alert System for use when the car is operating at low speeds to alert pedestrians to the car's presence. Second generation (2016–2019) The second generation Chevrolet Volt was officially unveiled at the January 2015 North American International Auto Show. Retail deliveries began in the United States and Canada in October 2015 as a 2016 model year, with 1,324 units delivered in the U.S. that month. Availability in the American market was limited to California and the other 10 states that follow California's zero emission vehicle regulations. GM scheduled the second generation as a 2017 model year to be released in the 39 remaining states by early 2016. Manufacturing of the 2017 MY Volt began in February 2016, and the first units arrived at dealerships at the end of February 2016. The 2017 model complies with stricter Tier 3 emissions requirements and was available nationwide. The second generation Volt has an upgraded powertrain with a 1.5-liter engine that uses regular gasoline; the 18.4 kWh battery pack has new chemistry that stores 20% more electrical energy and uses fewer cells, 192 compared with 288 on the 2014 Volt; it uses a new power controller that is integrated with the motor housing; the electric motors weigh less and