United Auto Workers union member assembly workers work on a Chevrolet Volt electric vehicle at General Motors Detroit-Hamtramck assembly plant in Hamtramck, Michigan July 27, 2011. REUTERS/Rebecca Cook (UNITED STATES – Tags: TRANSPORT BUSINESS EMPLOYME

United Auto Workers union member assembly workers work on a Chevrolet Volt electric vehicle at General Motors Detroit-Hamtramck assembly plant in Hamtramck, Michigan July 27, 2011. REUTERS/Rebecca Cook (UNITED STATES – Tags: TRANSPORT BUSINESS EMPLOYME

United Auto Workers union member assembly workers work on a Chevrolet Volt electric vehicle at General Motors Detroit-Hamtramck assembly plant in Hamtramck, Michigan July 27, 2011. REUTERS/Rebecca Cook (UNITED STATES – Tags: TRANSPORT BUSINESS EMPLOYMENT)