A critically injured motorist's dog kept her rescuers at bay for an hour after she slammed into the back of a Los Angeles city bus, authorities said. Mary Joy, 35, of Los Angeles was traveling about 35 m.p.h. on Venice Boulevard when she skidded into a stopped city bus, police said. Joy's car crumpled on impact, police said, and she suffered major head injuries. Paramedics were called immediately, but it took them an hour to get to Joy because her large Doberman pinscher sat snarling and snapping on her lap, police said. "Any time we tried to take the woman out, the Doberman would lunge at us," Officer David Krempa said. A fireman finally hooked it by the collar and Krempa pinned it to the floor of the passenger side with his baton, he said.