We have two basic classes of vehicles at the station : those with license plates SI-xxx, and those with more complex plate numbering, beginning GS-xxxx. The SI vehicles are all military surplus and, though well maintained, are old and well-worn. Bear this in mind when you drive them. All of the SI pickup trucks and small 4-wheel-drive vehicles on the mountain are fair game to use at any time to go between mountain sites and to the base camp (but do not take any vehicle from the MMT site without asking). Do not use any heavier vehicles (trucks, loaders, forklifts, etc.) without asking a support person for permission and checkout, even if you are experienced in operating that kind of vehicle.
On the mountain, leave the keys in every observatory vehicle, all the time. Someone may need the vehicle in an emergency, or at the least have a need to move it. If you wish to go to sleep with some assurance that there will be a vehicle for you to use when you get up (e.g., to go down on the way to catch a plane), tape a note to the steering wheel stating your need.
Some SI vehicles are kept at the base camp for off-premises trips. If you have a need to go to Tucson or Green Valley, reserve one of these vehicles in advance by calling Danny or Cesar. The GS-license vehicles are leased from a U.S. government motor pool to provide us with reliable transportation up and down the mountain. They are used for all the regularly-scheduled shuttle trips to the mountain, and as many other trips as can be covered. Danny and Cesar try to keep fairly close track of the whereabouts of all of these vehicles, so you should not take one anywhere without first checking with them, except in emergency.
Radio communication is an important aid to safety on the mountain road, and the GS vehicles generally have radios permanently mounted. At the start of any trip up or down, announce yourself on the radio, giving your name, route, and type of vehicle. Listen to all the other traffic, and if it appears that you will be meeting oncoming vehicles, announce your position every few kilometers along the road. Whenever you go any farther than to the MMT in one of the SI vehicles, take a portable radio (there is one in the IOTA building, and one in the Common Building) and use it.
Observatory drivers are fairly faithful (though not 100%) about using the radio. Remember, though, that the road below the gate is open to the public at all times. On weekends, particularly, you may expect public traffic, including some reckless drivers (and all without radios). Be on guard, therefore, at all times.