Air Lock to Air Lock Transfers
Vehicle in Pressurized Garage
The headline of the section just about states the entire option. The garage would be an Air Lock chamber. The colonist would don and pressure check his space suit as a safety precaution. Carrying his gloves in his helmet, he would enter the garage/air lock and seal the inner door. He would enter the vehicle, close its air tight door and, by remote control, pump down the air lock pressure to a vacuum. Then he would open the outer air lock door, drive wherever he needs to go and close the outer air lock door.
There are a few problems with the above scenario. One, the air lock would need to be rather large to accommodate a vehicle, and particularly the door, a disproportionately expensive part, would need to be rather large. Since the pressure cannot be economically pumped to the pressure of the ambient lunar vacuum, some gas would be lost at every cycling of the air lock. The bigger the air lock the greater the loss. Two, it would be difficult to arrange procedures so no significant moisture would be lost with the pressurizing gas and with moisture adsorbed in the dust that would cling to the vehicle. Three, the vehicle also would track dust into the air lock from whence it might later be tracked into the colony in general.
Go to Vehicle in a Space Suit
The colonist would don and pressure check his space suit. Then he would enter an air lock wearing the suit, close the inner door, pump down the pressure of the air lock and open the outer door. He would exit the air lock, close the outer door, walk to the unpressurized vehicle, enter, close the air tight door and pressurize the vehicle; or he would walk to a pressurized vehicle and enter by cycling an air lock. Then he would drive wherever he needs to go.
There are a few problems with this scenario also. One, the air lock though smaller than a garage, would still not be pumped down to the pressure of the ambient lunar vacuum, some gas would be lost at every cycling of the air lock. Two, it would still be difficult to arrange procedures so no significant moisture would be lost with the pressurizing gas and with moisture adsorbed in the dust that would cling to the space suit. Three the space suit boots also would track dust into the air lock from whence it might later be tracked into the colony in general and they would track dust into the vehicle.
Air Lock to Air Lock Transfer
In this case the vehicle door would be pressed against the air lock door of the colony building. The frame of the Colony air lock door could be recessed into the wall and the vehicle door frame could extend into this recess with a close enough fit that the vehicle and building could be mated with an air tight seal using a polymer gasket. Then the colonist in his pressure checked suit carrying his gloves in his helmet would open the inner air lock door, enter the airlock, close the inner door (for safety), open the outer air lock door (which in this case is hinged to swing inward), open the vehicle door and enter the vehicle. Then he would close the vehicle door, remotely close the outer air lock door, pump down the small volume between the colony air lock door and the conformal vehicle door to a vacuum, demate the vehicle from the colony air lock and drive wherever he needs to go. In this case the smallest volume would need to be pumped down to vacuum pressure with the smallest attendant gas loss. Neither the vehicle wheels nor the space suit boots would track dust into the air lock. Colonists might use a solution like this to enter vehicles and drive around Luna.
The inside the vehicle would correspond with the atmosphere pressure inside the lunar colony. Using this method the colonists would not have to spend time pre-breathing a new pressure.
Other Portrayals of a Similar Concept
Some architectures allow an external space suits that can keep the dust outside, such as "NASA's New Moon Rover". It was planned that an Altair lander launched on an Ares V would bring a pair of "NASA's New Moon Rover"s to Luna at a time. Since there will be no Ares V, there will be none of the planned new rovers.
The idea behind the movement of a colonist from vehicle to space suit without intervention of the cycling of an airlock is not in principal different from the main topic of this article. A double set of doors and a mating seal between the two independent enclosed breathable atmospheres is necessary and at least one of the independent enclosures is mobile. It is not a new concept. A version of it was portrayed in the original Star Wars movie. Droids R2D2 and C3PO escape from a spaceship to the planet Tatooine in an escape pod that connects to the spaceship by such a system.