Module density 

Spatial density grid and Level-of-Service (LoS) analysis for transportation.

LoS is not a single metric – the Highway Capacity Manual (HCM) defines separate criteria for different facility types and modes:

Criteria type	Input metric	Typical use
PedestrianWalkway	Density (pax/m2)	Sidewalks, corridors (Fruin)
PedestrianStairway	Density (pax/m2)	Stairs, escalator approaches
PedestrianQueuing	Density (pax/m2)	Waiting areas, platforms
VehicularFreeway	Density (pc/km/ln)	Freeway segments
VehicularUrbanStreet	Delay (s/veh)	Signalized intersections, arterials
BicycleFacility	Events per min	Bike lanes, shared paths
TransitCapacity	Load factor	Bus, rail passenger loading
CustomLosCriteria	User-defined thresholds	Any metric

Architecture

The LosCriteria trait defines how a raw measurement is classified into a LosGrade (A through F). Built-in implementations cover the standard HCM facility types. Users can implement the trait for custom metrics.

DensityGrid is a spatial grid that counts agents per cell and can classify each cell using any LosCriteria implementation.

Usage

use rustsim_spaces::density::*;

let mut grid = DensityGrid::new(100.0, 50.0, 2.0);

for agent in model.agents() {
    grid.add_position(agent.x, agent.y);
}

// Pedestrian walkway LoS (Fruin / HCM)
let los = PedestrianWalkway.classify(grid.density_at(10.0, 20.0));

// Pedestrian stairway LoS
let los = PedestrianStairway.classify(grid.density_at(5.0, 3.0));

// Full statistics with a specific criteria
let stats = grid.statistics(&PedestrianWalkway);

// Vehicular delay-based LoS (not grid-based -- classify directly)
let los = VehicularUrbanStreet.classify(35.0); // 35 s/veh delay

grid.clear();

Structs

BicycleFacility

Bicycle facility LoS based on hindrance events per minute (HCM Chapter 24).

CustomLosCriteria

User-defined LoS criteria with custom thresholds.

DensityGrid

Spatial density grid for computing agents-per-square-meter.

DensityStatistics

Summary statistics from a density grid.

PedestrianQueuing

Pedestrian queuing area LoS based on density (HCM Chapter 24).

PedestrianStairway

Pedestrian stairway LoS based on density (HCM Chapter 24).

PedestrianWalkway

Pedestrian walkway LoS based on density (Fruin / HCM Chapter 24).

TransitCapacity

Transit vehicle LoS based on passenger load factor (Transit Capacity and Quality of Service Manual).

VehicularFreeway

Vehicular freeway LoS based on density (HCM Chapter 12).

VehicularUnsignalized

Unsignalized intersection LoS based on control delay (HCM Chapters 20 and 21).

VehicularUrbanStreet

Vehicular urban street and signalized intersection LoS based on control delay (HCM Chapters 16 and 19).

Enums

DensityGridError

Errors returned by density-grid validation.

LosCriteriaConfigError

Errors returned by custom LoS criteria validation.

LosGrade

Level-of-Service grade A through F (HCM convention).

Traits

LosCriteria

Trait for classifying a raw measurement into a LosGrade.