Failure to yield the right of way
One of the leading causes of accidents, hands down, is failure to yield the right of way. The Insurance Institute for Highway Safety says that it's the top cause of accidents among drivers aged 70 and older, particularly on freeway merge ramps. In Uncommon Carriers, his book about long haul truckers, John McPhee points out that space cadets in the merge lane are a constant source of teeth-grinding anxiety for the people driving 80,000-pound big rigs. Another facet of failure to yield that's more prevalent in cities is running stop signs and red lights. Drivers coming from other directions expect the intersection to be clear when the light on their end turns green. Once again, predictability is good.