Crate map_model

Expand description

map_model describes the world where simulations occur. Importing a map from OSM partly happens in convert_osm and here.

Helpful terminology:

ch = contraction hierarchy, for speeding up pathfinding
degenerate intersection = only has 2 roads connected, so why is it an intersection at all?
lc = lane-change (which is modelled very strangely: https://a-b-street.github.io/docs/tech/trafficsim/discrete_event/index.html#lane-changing)
ltr = left-to-right, the order of lanes for a road
osm = OpenStreetMap

Map objects are usually abbreviated in method names:

a = area
b = building
tr = transit route
ts = transit stop
i = intersection
l = lane
pl = parking lot
r = road
ss = stop sign
t = turn
ts = traffic signal

Modules§

city 🔒
connectivity
edits 🔒: Once a Map exists, the player can edit it in the UI (producing MapEdits in-memory), then save the changes to a file (as PermanentMapEdits). See https://a-b-street.github.io/docs/tech/map/edits.html.
make 🔒: See https://a-b-street.github.io/docs/tech/map/importing/index.html for an overview. This module covers the RawMap->Map stage.
map 🔒: A bunch of (mostly read-only) queries on a Map.
objects 🔒
osm: Useful utilities for working with OpenStreetMap.
pathfind 🔒: Everything related to pathfinding through a map for different types of agents.
traversable 🔒

Structs§

AccessRestrictions
Amenity: A business located inside a building.
Area: Areas are just used for drawing.
AreaID
Building: A building has connections to the road and sidewalk, may contain commercial amenities, and have off-street parking.
BuildingID
City: A single city (like Seattle) can be broken down into multiple boundary polygons (udistrict, ballard, downtown, etc). The load map screen uses this struct to display the entire city.
CompressedMovementID: This is cheaper to store than a MovementID. It simply indexes into the list of movements.
ControlStopSign
ControlTrafficSignal: A traffic signal consists of a sequence of Stages that repeat in a cycle. Most Stages last for a fixed duration. During a single Stage, some movements are protected (can proceed with the highest priority), while others are permitted (have to yield before proceeding).
Crossing
DiagonalFilter: A diagonal filter exists in an intersection. It’s defined by two roads (the order is arbitrary). When all of the intersection’s roads are sorted in clockwise order, this pair of roads splits the ordering into two groups. Turns in each group are still possible, but not across groups.
DirectedRoadID
EditEffects
EditIntersection
EditRoad
ExtraPOI: Extra point-of-interest
Intersection: An intersection connects roads. Most have >2 roads and are controlled by stop signs or traffic signals. Roads that lead to the boundary of the map end at border intersections, with only that one road attached.
IntersectionCluster: This only applies to VehiclePathfinder; walking through these intersections is nothing special. And in fact, even lanes only for buses/bikes are ignored.
IntersectionID
Lane: A road segment is broken down into individual lanes, which have a LaneType.
LaneID: A lane is identified by its parent road and its position, ordered from the left.
LaneSpec
Map
MapConfig
MapEdits: Represents changes to a map. Note this isn’t serializable – that’s what PermanentMapEdits does.
Movement: A Movement groups all turns from one road to another, letting traffic signals and pathfinding operate at a higher level of abstraction.
MovementID: A movement is like a turn, but with less detail – it identifies a movement from one directed road to another. One road usually has 4 crosswalks, each a singleton Movement. We need all of the information here to keep each crosswalk separate.
NamePerLanguage: None corresponds to the native name
OriginalRoad: Refers to a road segment between two nodes, using OSM IDs. Note OSM IDs are not stable over time and the relationship between a road/intersection and way/node isn’t 1:1 at all.
ParkingLot: Parking lots have some fixed capacity for cars, and are connected to a sidewalk and road.
ParkingLotID
Path
PathRequest
PathV2: A path between two endpoints for a particular mode. This representation is immutable and doesn’t prescribe specific lanes and turns to follow.
Pathfinder
PathfinderCache: For callers needing to request paths with a variety of RoutingParams. The caller is in charge of the lifetime, so they can clear it out when appropriate.
PermanentMapEdits: MapEdits are converted to this before serializing. Referencing things like LaneID in a Map won’t work if the basemap is rebuilt from new OSM data, so instead we use stabler OSM IDs that’re less likely to change.
Position: Represents a specific point some distance along a lane.
RawToMapOptions: Options for converting RawMaps to Maps.
Road: A Road represents a segment between exactly two Intersections. It contains Lanes as children.
RoadFilter: A filter placed somewhere along a road
RoadID
RoadSideID
RoadWithStopSign
RoutingParams: Tuneable parameters for all types of routing.
Stage
TransitRoute
TransitRouteID
TransitStop
TransitStopID
Turn: A Turn leads from the end of one Lane to the start of another. (Except for pedestrians; sidewalks are bidirectional.)
TurnID: Turns are uniquely identified by their (src, dst) lanes and their parent intersection. Intersection is needed to distinguish crosswalks that exist at two ends of a sidewalk.
UberTurn
Zone: A contiguous set of roads with access restrictions. This is derived from all the map’s roads and kept cached for performance.

Enums§

AmenityType: Businesses are categorized into one of these types.
AreaType
BufferType
BuildingType
CommonEndpoint
CrossingType: Classifies pedestrian and cyclist crossings. Note lots of detail is missing.
Direction
DrivingSide
EditCmd
EditIntersectionControl
ExtraPOIType
FilterType: The type of a modal filter. Most of these don’t have semantics yet; the variation is just for visual representation
IntersectionControl: The kind of traffic control present at an intersection.
IntersectionKind: What kind of feature an Intersection actually represents. Any connection between roads in the network graph is represented by an Intersection, but many of them are not traffic “intersections” in the common sense.
LaneType
OffstreetParking: Represent no parking as Private(0, false).
PathConstraints: Who’s asking for a path?
PathStep
PathStepV2: One step along a path.
PathfinderCaching: When pathfinding with different RoutingParams is done, a temporary pathfinder must be created. This specifies what type of pathfinder and whether to cache it.
RestrictionType
SideOfRoad: See https://wiki.openstreetmap.org/wiki/Forward_%26_backward,left%26_right.
StageType
Traversable: Either a lane or a turn, where most movement happens.
TurnPriority
TurnType

Constants§

MAX_BIKE_SPEED
MAX_WALKING_SPEED
NORMAL_LANE_THICKNESS
PARKING_LOT_SPOT_LENGTH: From some manually audited cases in Seattle, the length of parallel street parking spots is a bit different than the length in parking lots, so set a different value here.
SIDEWALK_THICKNESS

Functions§