By TOM KRISHER
AP Auto Writer
DETROIT (AP) — The head of the National Transportation Safety Board is expressing concern about the safety risks that heavy electric vehicles pose if they collide with lighter vehicles. Jennifer Homendy raised the issue in a speech Wednesday in Washington to the Transportation Research Board. She noted, by way of example, that an electric GMC Hummer weighs about 9,000 pounds, with a battery pack that alone weighs 2,900 pounds — roughly the entire weight of a typical Honda Civic. The extra weight that EVs typically carry stem from the outsize weight of their batteries. To achieve 300 or more miles of range per charge from an EV, batteries have to weigh thousands of pounds.