Depends on the location and environment too, people do get hit. City is probably the most dangerous but in some ways i think the middle is most dangerous, a fairly crowded place with medium constant traffic and no bike accommodations. Cities are busier but have some accommodations and slower traffic. In the boonies, you have space and may not see any cars all day. In the suburbs you may have some quiet roads but I think some roads people shouldn't be riding. There's no room, cars are going too fast, the roads curve all over and its busier and busier every year. Mountain biking is inherently dangerous too but you're a little more in control and there's everything from smooth flat dirt trails to going straight down a mountain.