At least four people were killed and several others injured in separate road accidents in different parts of the state due to dense fog last night and Wednesday morning. One person was killed and at least 15 others were injured when three buses, a container truck and two cars collided on the Agra-Lucknow Expressway last night in Unnao district, adjacent to the state capital. Bangarmau police station SHO Gyanendra Singh said, “A bus collided with a container truck from behind due to low visibility due to heavy fog. “Later, two other buses collided with the bus and then two cars collided with each other, resulting in a head-on collision.”