unique identifier for rule

Rules can be characterized by the category that they are placed into. For example, Annex D provides a list of potential rule categories that can be used to manage which rules are retrieved via METR.

private, governmental, perhaps private-government approved

The rule-maker that issued the rule.

Some rules (e.g., warnings related to scaffolding on sidewalks) can be associated with permits, including a type of permit and permit issuer.

A rule can include information on who is authorized to enforce the rule (e.g., the towing company where a towed vehicle can be found).

A rule can include information about the penalties that can apply upon enforcement action (e.g., a maximum fine or fines doubled).

Many rules are associated with locations, which might be defined by a point location; a linear location; an area location, including a custom area or an entire jurisdiction. For example, rules might include stop signs (i.e., point locations), on-street parking restrictions (i.e., linear locations), congestion zones (i.e., a custom area location), and rules related to the use of headlights (i.e., jurisdictional area locations).

Some rules are only applicable to users that have a particular heading. For example, some northbound lanes might only have vehicle occupancy rules in the morning while southbound lanes only have vehicle occupancy rules in the evening.

Some rules need higher mapping resolutions to be properly interpreted; the level of mapping resolution needed would need to be conveyed as a part of the rule. For example, some rules might specify exact location of restrictions such that users would need a higher resolution map to ensure compliance.

A rule can be associated with a schedule, hours of applicability, fuzzy times (e.g., "dawn", "holidays"), applicable days of week, applicable start and end dates, and other temporal constraints.

Some rules only apply to certain classifications of roads/pathways. For example, an urban residential road is likely to have a different default speed limit than a rural motorway. 

Some rules apply to roads with certain pavement types. For example, gravel roads might be associated with a lower speed limit.

Some rules apply to a specific set of vehicle classifications. For example, heavy vehicles might be restricted to certain lanes on a motorway.

Some rules apply to the physical dimensions of a vehicle, such as its length, width, and/or height. For example, tall vehicles might be restricted from entering a tunnel.

Some rules apply to the mass (or weight) of a vehicle. For example:

1. a bridge might prohibit vehicles above a specific weight
2. a jurisdiction might require special registration of vehicles more than a specified mass

Some rules apply to vehicles that are associated with an official permit. For example: 

1. a vehicle might be issued a permit to park (or be parked) near the owner's residence 
2. a vehicle might be equipped with a toll tag that allows it to use a tolled facility

NOTE: A vehicle permit is associated with the vehicle irrespective of the current occupants. Vehicle permits can be associated with expirations that occur due to time or due to change in registration.

Some rules apply to vehicles with specific certification, which might be granted on a make and model basis. For example, a jurisdiction might require ADS Level 4 vehicles to have distinct certificates to operate in specific environments, such as for:

1. motorways, 
2. roundabouts, 
3. traffic circles,
4. a specific (e.g., complex) interchange

Some rules apply to vehicles based on the fuel type that they are using. For example, a central business district might restrict vehicles that are using diesel fuel.

Some rules apply to vehicles based on their emissions profile. For example, an emission control zone might be restricted only to vehicles that meet ultra low emission vehicle standards.

Some rules apply to equipment that is associated with the vehicle. For example access to a road might be restricted to vehicles with snow chains.

Some rules apply to vehicles with trailers. For example:

1. a jurisdiction might restrict the number of trailers that can be attached to a vehicle
2. a vehicle with a trailer might be restricted from using a specific roadway
3. a vehicle with a carrier on the back might be required to have additional reflectors to designate the end of the carrier.

Some rules apply to a particular usage of a vehicle regardless of an official permit. For example: 

1. some lanes on a motorway might be restricted to high occupancy vehicles
2. a segment of kerbside might be restricted for passenger loading and unloading

Some rules only apply to vehicles based on their cargo. For example, vehicles carrying dangerous goods might be restricted from entering a tunnel.

Some rules apply to a vehicles associated with an official permit related to vehicle usage. For example, a stretch of kerbside might be restricted to vehicles with permits related to ridesourcing operations.

Some rules apply to particular classifications of users. For example:

1. Commercial vehicle operators might be required to stop at check points
2. Police officers and emergency responders might be allowed to use turn around lanes on a motorway

Some rules apply to a users associated with an official permit. For example:

1. a user might be issued a permit to park a vehicle near the user's residence 
2. a user might be issued a permit to park in accessible parking spaces

NOTE: A user permit is associated with the user and can be moved between vehicles as needed.

The meaning and/or activity status of some rules (e.g., signal timing, pull over for emergency vehicle, lower speed when raining) is dependent upon supplemental data. The rules need to identify such cases along with the acceptable source(s) for the supplemental data.

Some rules only apply when certain environmental conditions are present. For example:

1. lower speed limits might apply during rain
2. parking restrictions might take affect due to snow 
3. certain vehicles might be restricted when air pollution exceeds certain levels

Some rules only apply when certain external conditions exist that might be difficult for vehicle-based sensors to detect. For example, speed limits might be reduced when workers or children are present.

Some rules only apply when certain emergency conditions exist that might be difficult for vehicle-based sensors to detect. For example, access to specific streets might be restricted due to a terrorist threat level

Some rules might apply only when on-board sensors detect specific conditions (e.g., rain detected, driver fatigue detected).