Right-of-Way - Valen Heavy Industries

There is no hard-and-fast rule about right-of-way for vehicles in Second Life. I have assembled these recommendations based on 14 C.F.R. § 91.115 - Right-of-way rules: Water operations, the U.S. Coast Guard Navigation Rules, and my own knowledge as a certificated private pilot.

Aviation, road, and maritime rules are ALL based on the concept of yielding right-of-way to the less maneuverable vehicle (or person.) You will see this in the FAR/AIM, in sailing manuals, and even on signs posted on public trails. They are NOT designed to entitle operators of one class of vehicle (or pedestrians) to expect unreasonable privileges over those operating another class of vehicle. These recommendations are designed around pragmatism, not entitlement.

Furthermore, these recommendations are not the law. No one HAS to obey them. They are presented in the hope that they will help vehicle operators to avoid contention, and to AMICABLY resolve it where it occurs. If a sim owner has their own published set of rules, those will naturally override anything here. Over land owned by Lindens and 3rd parties without any vested interest in a conflict between two vehicle users, this set of recommendations is quite reasonable & should be considered.

General

See-and-avoid applies to ALL vehicle operators. In no way shall right-of-way considerations entitle anyone to deliberately cut in front of someone else, or through inaction allow a collision.
"Vessel" and "vehicle" are used here interchangeably.
A vehicle which is at a full stop - parked, anchored (if so equipped), etc. - shall have the right-of-way in every situation, no matter what. However, the act of becoming stopped, and of resuming motion, matters. The operator of a stopped vehicle shall not use this expectation as leverage to operate recklessly. Setting the vehicle in motion cancels this particular right-of-way condition. The operator shall not set the vehicle in motion, or through inaction (failing to set the parking brake, disabling physics if it's subject to wind or water current, etc.) allow the vehicle to move, until any transiting traffic is well clear. Furthermore, a vehicle operator shall not deliberately stop in a way that hinders other vehicles. There shall, for example, be no parking on a taxiway, stopping in front of someone else's dock, or immediately stopping in front of another vehicle you know to be on a collision course.
A vehicle being overtaken (passed) has the right-of-way in all situations.
Two moving vehicles on a collision course shall both deflect to the RIGHT, keeping WELL CLEAR.
Vehicles engaged in combat should generally be avoided by non-combatant vehicles. They shall avoid shelling, torpedoing, ramming, or in any other way colliding with other vehicles.
When two vehicles are crossing each others' paths, the one to the RIGHT has right-of-way. It's the same as rolling up to a four-way stop in a country where cars are driven on the right side of the road.

Aircraft and boats are sometimes equipped with nav lights. Generally, on the left (port) side will be a red light, and on the right (starboard) side will be a green, blue, or white light. Treat this like a stoplight. If the nav light closest to you is RED, then YIELD. If the light closest to you is NOT RED, you have the right of way.
Aircraft designers are advised to use the RED/GREEN system, if they are implementing nav lights. Starboard nav lights in colors other than green are not standard for aircraft.

Crowds and Events

Unless an event is officially sanctioned & given exclusive rights to simulator use by the party governing the simulator in question, no person, group, or event has presumptive priority over any other person, group, or event. With a shared resource, such as Linden land, it is important to recognize this, and to use courtesy to resolve any contention.
A pilot-in-command who happens upon a crowd shall exercise due caution to avoid colliding with members of the crowd (and their vehicles, if any.) If the crowd is a fleet of airplanes, boats, ground vehicles, etc., the PIC is requested to stay well clear, unless the PIC can reasonably expect to be welcomed at the event. If a PIC finds himself or herself inadvertently in the middle of an event, he or she is requested to take immediate action to secure the airplane from interfering with the event. This may mean opening or closing the throttle, executing a tight turn, climbing, descending, or simply going into edit mode and manually moving the airframe out of the way.

Ground Operations

The pilot-in-command (PIC) shall take all precautions to avoid colliding with avatars, other vehicles, and movable objects.
As airplanes are much wider than ground vehicles, which poses challenges in maneuverability, operators of ground vehicles are requested to yield right-of-way to aircraft while on airport grounds. However, pilots shall not use this expectation to operate their vehicles recklessly.
Airplanes operating on roads (off-airport) are requested to yield right-of-way to ground vehicles as much as possible.

Taking Off and Landing

Landing aircraft have right-of-way over departing aircraft.
Pilot-in-command shall, before entering the runway, scan the area to make sure no one is landing. Use the mini-map to check for green dots, and trust that over what you see, even if you have a high draw distance.
If two aircraft are landing in the same place, the aircraft at lower altitude has right-of-way, EXCEPT that it shall not use this status to cut in front of another aircraft that is closer to the landing area.
Unpowered gliders subject to realistic physical constraints, motorgliders or other airplanes operating with their engine(s) stopped, and helicopters in autorotation, shall have right of way over all powered craft.
Seaplanes shall take care to scan the section of water they will be taking off from or landing on. They shall consider other vehicles in the area and their apparent trajectories, and select a takeoff or landing course that will not impede navigation of other vehicles. However, other vehicles, noticing that a seaplane is taking off or landing, shall not deliberately cut in front of it.

In the Air

The rules of collision avoidance in the air are the same as they are on the ground. If two aircraft are on a head-on collision course, they shall both execute a right turn. If two aircraft are crossing paths, the one to the right shall have the right of way. Again, if the aircraft has nav lights in the correct (standard) configuration: If the green nav light is closer, you have the right of way. If the red nav light is closer, the other aircraft has the right of way.
Being in an air race, conducting aerobatic maneuvers, etc. is not an excuse to ram into avatars or other vehicles.
Pilots are encouraged to use VFR flight levels:

Above 300 meters absolute altitude (the Z component of your position as reported on the menu bar - not your altitude above ground or sea level), use the ONE rule. Use an ODD numbered altitude in hundreds of meters if you are travelling NORTH or EAST (heading 1 to 179) and an EVEN numbered altitude in hundreds of meters if you are travelling SOUTH or WEST (heading 180 to 360.)
Example: You are traveling EASTBOUND at a heading of 87. You are flying according to visual flight rules. Fly at 550, 750, 950, 1150, etc. meters.
Example: You are traveling WESTBOUND at a heading of 280. Fly at 450, 650, 850, 1050, etc. meters.
IFR flight levels are "flat." This would be 400, 500, 600, 700, etc. SL does not currently have an adopted instrument flight rules system.
Try to remain within 100 meters of your appropriate flight level. If you want to stick to FAR/AIM regs, stay within 100 feet (about 30 meters.)

If you are overtaking an aircraft at the same flight level, pass on the RIGHT. If you are overflying an airfield, stay to the RIGHT of it.

On the Water

Unless the sim owner has established rules to the contrary, the presence of wings on a vessel does not place it in a different class than other vessels. Unless it is unpowered (such as a glider), an airplane or rotorcraft shall be considered in the same class as a motorboat.
The highest right of way privilege shall be afforded to vessels that are at a full stop or uncommanded, regardless of powered/unpowered status. This is subject to the provisions in the General section, above - vehicles shall not be stopped in such a way as to deliberately impede other vehicles, and shall not suddenly resume motion in a way that would interfere with other vehicles.
Exceptionally large vessels, particularly those with realistic rudder authority, shall be afforded high priority in right-of-way situations. However, operators of these vessels shall not use this expectation to operate their vessels recklessly.
When a seaplane encounters a POWERED BOAT, including another seaplane with its engine running:

To avoid a head-on collision, vessels shall each deflect to the right, as with ground and air operations.
To avoid a collision when crossing paths, the vessel to the right has right-of-way, as with ground and air operations. Pay attention to nav lights (if any, and assuming the vehicle designer implemented them in the standard way.)

When a seaplane encounters an UNPOWERED BOAT, the pilot-in-command shall yield right-of-way to the boat. However, the boat captain shall not use this expectation as a justification to operate recklessly.
To qualify as an unpowered boat, a vessel must move only according to the interaction of simulator wind - as measured by llGetWind() - with its sail(s), in combination with its rudder and any other relevant control surfaces. Alternately, a sailboat operating on a course with a "standard" wind direction and velocity, such as an established race course, qualifies as unpowered as long as its captain adheres to that wind direction and velocity, and is not using an engine, thrust augmentation attachment, etc. to modify the vehicle's operation.

A "sailboat" that allows acceleration in any direction with no regard to simulator wind, is having its wind direction manipulated in a way that gives it the same maneuverability as a powered boat, is not adhering to published wind settings for the course it's on, can turn at an unrealistically fast rate, or demonstrates any other unrealistic behavior, shall be considered powered. The mere presence of sails and absence of a propeller or jet pump does not, by itself, class a vessel as unpowered. The physics system implemented on the boat needs to be authentic with regard to wind, sails, and rudder. A normally unpowered sailboat that has a power head, jet pump, etc. deployed and turned on, shall be considered powered as well, even if it is still picking up thrust from its sails.
The pilot in command shall remain clear of any vessel the pilot knows to be unpowered, although the captain of an unpowered vessel shall not take advantage of this expectation to operate their vessel recklessly.
As a "good neighbor" effort, pilots in command are requested to yield right of way to boats at all times, regardless of whether they are powered or not. However, boat captains shall not use this courtesy as an excuse to operate recklessly.