Cadillac Woman
Picture this. There are four lanes of traffic waiting for the light at Government Center. The two right lanes are stopped at the red light while the two left lanes are stopped for a red left-turn arrow. As we wait in the second lane to go straight through, two more cars wait in the fourth lane for the left turn. From behind, a big old Cadillac driven by a gray-haired woman comes up in the empty lane three. Without even pausing for the red left-turn arrow, she makes a complete u-turn, going around the two waiting cars to drive back in the direction she just came. Now there was no oncoming traffic, but what makes someone even think of doing that, never mind actually performing the maneuver. This lady rates a whole new category on the dangerous driver test.