Social Distancing Metrics

LEGION social distancing supports analysis of up to 3 different social distances at once.

Social distances are defined in Project Settings, under the Social Distancing tab.

The Social Distancing field defines the default distance used by the various social distancing tools.

This value may be overridden in each social distancing tool.
Changing the value here will affect any social distancing tool where the default has not been overridden.

Entity Proximity Metrics provide analysis of count and time within social distance. Three categories of metric exist:

Proximity Count – for an entity, the number of other entities within social distance(s).
Instantaneous value.
Current Breach Duration – for an entity, the length of time that the count of other entities, above a predefined threshold, have been within social distance(s).
Pseudo-instantaneous value – for an entity, time accumulates until the number of other entities within social distance(s) drops below a defined threshold.
Total Breach Duration – for an entity, the total duration of all recorded Entity Proximity Breach Times.
Cumulative value.

Simultaneous analysis of up to 3 different social distances is possible, depending on the "SD" metrics enabled in Project Settings. Each Entity Proximity Metric is prefixed with its SD identifier, e.g. for SD1, the Entity Proximity Metrics are:

SD1 Proximity Count
SD1 Current Breach Duration
SD1 Total Breach Duration

Metrics SD1, SD2 and SD3 can be customised to between 0.6m and 10m:

All SD1, SD2 and SD3 metrics support a customizable Breach time threshold. For each entity, this is minimum number of other entities within social distance needed to increment Current Breach Duration.

The default value is zero, meaning any entities within social distance of another entity contribute to breach time;

Example:

SD1 specifies a breach time threshold of 3 entities. 1 or 2 entities within social distance of an entity will not contribute toward Current Breach Duration Time. 3 or more entities within social distance of an entity will contribute 0.6s toward Current Breach Duration.

Note: The actual number of entities within social distance per time step does not affect how much breach time is accumulated per time step. It simply affects whether or not breach time is accumulated for a given time step. So, whether a single entity or ten entities are within social distance in a given time step, only 0.6s is added to Entity Proximity Breach Time

Use obstacles as isolating walls ('wall check') determines how obstacles affect Entity Proximity Metrics.

By default, the calculations for Entity Proximity Metrics ignore obstacles between entities. This is useful for barriers which obstruct movement but do not physically prevent people from coming into contact. For example:

A wall between two rooms counts as an isolating wall. People may be able to see each other through a window in the wall but cannot make physical contact. These obstacles should be included for wall checks.
Rope barriers defining a corralled queue are not isolating walls. People can still come into contact with others across these barriers. These obstacles should be excluded for wall checks.

To consider obstacles when calculating Entity Proximity Metrics, please tick the box Use obstacles as isolating walls, then place a tick in the Enable column for each CAD Layer you want to use for wall checks. For example:

Note: Good practice is to use separate CAD Layers for wall check obstacles. Wall checks can reduce simulation speed, because more calculations are being performed. To maximise performance, please limit selection of wall check obstacles to just the essential CAD elements.