DaimlerChrysler plans to start selling a four-wheel-drive vehicle that will make the largest family vehicles now on the road seem tiny — nay, minute — in comparison. The vehicle, dubbed the Unimog, will be 20 feet long and 9 feet 7 inches tall; the front seat is reached by a three-step ladder. It is almost three feet taller than the tallest SUV, and a foot longer then the Ford Excursion. It weighs over six tons, more than the weight of two Chevrolet Suburbans. The Unimog gets about 10 miles to the gallon on diesel fuel, worse than any SUV. In contrast, the Honda Insight, a gas-electric hybrid car, is 12 feet 11 inches long and 4 feet 5 inches tall; it gets about 65 miles to the gallon on gasoline.