Bison burned in one of Yellowstone's hot spots manages to outrun a grizzly, as captured in a dramatic sequence on the road: http://www.ktvq.com/news/the-bison-got-away/
The bison was put down the next day because of extent of injuries.
Can you imagine what it was like when millions of bison AND 10's of thousands of grizzly bears both roamed the Great Plains ? ...and now that very same drama being played out on asphalt highways of the 21st century. Weirdly ironic in a way?