Hlaup.is took a video on the course 3 km from the start. Each section shows runners in different colour groups, but there are always some that are slower and fall into the video of the following group, and some are faster and are then seen in the video of the previous group.
Group 1 - Yellow start group
.
Group 2 - Red start group
.
Group 3 - Green start group
.
Group 4 - Blue start group
.