In the context of a vehicle pursuit, what specific roles do

While in a vehicle pursuit, the most used roles are "primary" and "secondary". As a primary unit you are the first one in the pursuit chasing after a suspect. The main task of a primary unit is to keep eyes on the suspect. If you are the only unit attached to the pursuit or the secondary lost eyes, you also need to callout 10-20s. As a secondary, your role is to update everyone on location, direction, speed, weather conditions, traffic conditions and other relevant information. If more units are attached, they follow the pursuit and switch out with primary and secondary depending on terrain, weather, speed or other factors that means you need to step in for another unit. For example if another unit is involved in an accident.