Busy car park
The Dragon capsule is hooked by a robotic arm once it approaches close enough and is then coupled to an airlock in the middle of the ISS. The Soyuz Progress capsules dock automatically at the far end of the station where they can transfer liquids and fuel as well as boost the ISS and raise its orbit by firing the service module's main engines. This means there's no need for one cargo capsule to get out of the way of the other to find a parking space. Usually though the mission controllers don't like two ships manoeuvering around the ISS at the same time so they'll probably prioritise one docking operation over the other.
I think the record for number of cargo and passenger ships at the ISS at one time was six, including a Space Shuttle as well as an ATV launched by ESA but none of them docked while the others were still in free flight near the station itself.
Biting the hand that feeds IT
