Driver is usually the person with the agenda who keeps team together, focused on the task at hand and making sure team is going in the direction he wants.
If you want something done by your team then you need to be the driver.
In a team settings, we all know the importance being a leader, but unless leader is also the driver he will be ineffective. Just like when you plan a outing with your team and you decide to go somewhere, you will take your seat in the vehicle and wait for the driver to take you to the destination. From this point onwards the driver is in power to decide everything about the trip, till we reach the destination.
An effective leader is one who is also the driver of the team, or else have a drive dedicated to his’s vision, otherwise we will have an rubber stamp leadership in team. If driver is missing altogether from the team then it will not move in any direction and it will fail, just like the above outing if no one is going to drive the vehicle.