Crate sim[][src]

The sim crate runs a traffic simulation on top of the map_model. See also https://a-b-street.github.io/docs/tech/trafficsim/index.html.

The simulation is very roughly layered into two pieces: the low-level “mechanics” of simulating individual agents over time, and higher-level systems like TripManager and TransitSimState that glue together individual goals executed by the agents.

Helpful terminology:

Modules

analytics
events
make

Everything needed to setup a simulation. https://a-b-street.github.io/docs/tech/trafficsim/travel_demand.html for context.

mechanics
pandemic

An experimental SEIR model by https://github.com/omalaspinas/ glued to the traffic simulation. Transmission may occur when people spend time in shared spaces like buildings, bus stops, and buses.

recorder
render

Intermediate structures so that sim and game crates don’t have a cyclic dependency.

router

For vehicles only, not pedestrians. Follows a Path from map_model, but can opportunistically lane-change to avoid a slow lane, can can handle re-planning to look for available parking.

scheduler
sim
transit
trips

Structs

AgentProperties
Analytics

As a simulation runs, different pieces emit Events. The Analytics object listens to these, organizing and storing some information from them. The UI queries Analytics to draw time-series and display statistics.

BorderSpawnOverTime
CarID
CommutersVehiclesCounts

The number of active vehicles and commuters, broken into different categories.

CreateCar
CreatePedestrian
DistanceInterval
DrawCarInput
DrawPedCrowdInput
DrawPedestrianInput
ExternalPerson
ExternalTrip
IndividTrip
MapBorders

Lists all border intersections of the map, broken down by mode and whether they support incoming or outgoing traffic.

OrigPersonID
ParkedCar
PedestrianID
Person
PersonID
PersonSpec
Scenario

A Scenario describes all the input to a simulation. Usually a scenario covers one day.

ScenarioGenerator
SidewalkSpot
Sim

The Sim ties together all the pieces of the simulation. Its main property is the current time.

SimFlags

SimFlags specifies a simulation to setup.

SimOptions

Options controlling the traffic simulation.

SlidingWindow

A sliding window, used to count something over time

SpawnOverTime
TimeInterval
TripID
TripInfo
TripPhase
UnzoomedAgent
Vehicle
VehicleSpec

Enums

AgentID
AgentType
AlertHandler
AlertLocation
CarStatus
DelayCause

Why is an agent delayed? If there are multiple reasons, arbitrarily pick one – ie, somebody could be blocked by two conflicting turns.

DrivingGoal
ExternalTripEndpoint
ParkingSpot
PedCrowdLocation
PersonState
Problem
ScenarioModifier

Transforms an existing Scenario before instantiating it.

SidewalkPOI

Point of interest, that is

TripEndpoint

Specifies where a trip begins or ends.

TripMode
TripPhaseType
TripPurpose

Lifted from Seattle’s Soundcast model, but seems general enough to use anyhere.

TripResult
VehicleType

Constants

BIKE_LENGTH
BUS_LENGTH
FOLLOWING_DISTANCE

At all speeds (including at rest), cars must be at least this far apart, measured from front of one car to the back of the other.

LIGHT_RAIL_LENGTH
MAX_CAR_LENGTH
MIN_CAR_LENGTH
SPAWN_DIST

When spawning at borders, start the front of the vehicle this far along and gradually appear. Getting too close to EPSILON_DIST can lead to get_draw_car having no geometry at all.

Traits

SimCallback

Functions

fork_rng

Need to explain this trick – basically keeps consistency between two different simulations when each one might make slightly different sequences of calls to the RNG.