4x400m relay: USA win fifth successive Olympic title
The United States won their fifth successive Olympic gold in the women's 4x400m.
Deedee Trotter, Allyson Felix, Francena McCorory and Sanya Richards-Ross finished more than three seconds ahead of nearest rivals Russia.
Jamaica beat off the challenge of Ukraine to take the bronze medal.
Great Britain, who included Perri Shakes-Drayton and indivindual 400m silver medallist Christine Ohuruogu in their line-up, finished fifth.
The victory for the USA gives Felix her third gold of the Games following her wins in the 200m and 4x100m relay.
USA were the fastest team in qualifying, finishing a second a head of nearest rivals Russia, and they continued their good form.
Victory never looked in doubt after the first changeover and the remaining trio edged further clear of the rest of the field.
Richards-Ross, who won gold in the individual 400m, then carried the baton home, as they finished just 1.8 seconds outside the world record. The top six teams all ran a season's best time on the night.