Stress rules

Level of Traffic Stress (LTS) is assigned by two decision tables — data, not code. This page is the reference for their structure and the terse authoring form; for the model (what LTS 1–4 mean, how segment and intersection stress combine) see How stress works, and for a worked edit see the Edit stress rules tutorial.

The two built-in rule sets ship under bikescore-bna/rules/data/ and are carried into every complete scenario:

Ruleset	File	Produces	Config field
Segment stress	segment_stress.yaml	ft_seg_stress, tf_seg_stress	config.stress.segment_rules
Intersection stress	intersection_stress.yaml	ft_int_stress, tf_int_stress	config.stress.intersection_rules

Both run inside the stress stage over the segment table (columns like adj_fc, speed_limit, ft_lanes, ft_bike_infra, plus the node attributes). The final per-segment LTS is the max of its segment and intersection stress in each direction.

Anatomy of a ruleset

name: segment_stress
sets:                     # named value lists reused across rules
  primary_fcs: [primary, primary_link]
passes:
- name: seg_stress
  for:                    # fan a whole pass over directions — <dir> expands to ft, tf
    dir: [ft, tf]
  rules:
  - id: motorway_trunk
    when: { adj_fc: $motorway_trunk_fcs }   # $name references a set
    set:  { <dir>_seg_stress: 3 }
  - id: residential
    when: { adj_fc: residential }
    rules:                # nested rules: only evaluated when the parent `when` holds
    - id: residential_low
      when: { speed_limit: { le: 25 } }     # operators: le, ge, lt, gt, in, ne …
      set:  { <dir>_seg_stress: 1 }
    - id: residential_high                   # no `when` → the fall-through default
      set:  { <dir>_seg_stress: 3 }

Key constructs:

• First match wins. Within a pass (or a nested rule block), rules are tried top to bottom; the first whose when matches sets the value. A trailing rule with no when (or a pass-level default:) is the fall-through.
• sets are named value lists; a condition references one with $name instead of inlining the list, so the same list is authored once.
• for: fan-out repeats a pass or rule block over each value of a loop variable, substituting <var> in ids, conditions, and set targets. dir: [ft, tf] is how one authored rule covers both travel directions; nested for: { fcg: [...] } covers functional-class groups (see segment_stress.yaml).
• Nested rules under a rule are scope-gated: they are only reached when the parent's when holds, which keeps deep tables compact.
• predicates (intersection ruleset) are named condition bundles referenced by use: name, e.g. unprotected_ft.
• after: on a pass orders it explicitly after another pass — e.g. int_stress_link_reset runs after int_stress to reset link roads to LTS 1.

Inspecting and overriding

The rulesets are just fields on the config. A complete scenario carries its own copies, so the way to change stress assignment is to edit the ruleset inside a scenario (or derive a new scenario from default) — see the tutorial and Customize stress. Rule authoring uses the shared decision DSL described in Extensibility; the same terse form drives the road-attribute and destination-matcher rules.