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Exercise: Barricaded related vs barricaded sameline

This exercise demonstrates a subtle but high-impact rule under DoD 4145.26: a barricade only changes the analysis when the PES and ES sit on the same operating line. Across parallel operating lines, the unbarricaded ILD applies whether or not a barricade exists between them.

Learning objectives

By the end of this exercise you should be able to:

  • Identify when K9 (barricaded ILD) versus K18 (unbarricaded ILD) governs
  • Recognize that "related" status has an impact on barricade reduction
  • Read the analysis path the engine produces for each result, and locate the criteria references that anchor the K9 vs K18 decision

Background​

Under 4145.26, intraline distance (ILD) reduces from K18 to K9 when an effective barricade exists between a PES and an ES and the two are on the same operating line. That reduction is only available when the relationship code is sameline. A pair with the related code — related, but on parallel operating lines — falls back to K18 even when a barricade physically sits between them.

This is one of the most common modeling mistakes — a user adds a barricade, expects the arc to shrink, and is surprised when nothing changes. See Relationships for the full taxonomy of relationship codes.

Prerequisites​

Scenario A: Same operating line (barricade reduces)​

[TODO: FILL IN — exact field names from calculator UI for operating-line assignment.]

  1. Create a PES and an ES with the relationship set to Same Operating Line (sameline)

  2. Set the explosive quantity on the PES to a value above the barricaded ILD threshold

  3. Run the analysis with no barricade between the two facilities

  4. Note the analysis code (K18) and the resulting required distance

  5. Add a barricade between the PES and the ES

  6. Re-run the analysis

  7. The analysis code switches to K9 and the required distance decreases

Scenario B: Parallel operating lines (barricade has no effect)​

  1. Create a new PES/ES pair with the relationship set to Related (related) — related, but on parallel operating lines

  2. Use the same explosive quantity as Scenario A

  3. Run the analysis with no barricade

  4. The analysis code is K18 and the required distance matches the unbarricaded result from Scenario A

  5. Add a barricade between the PES and the ES

  6. Re-run the analysis

  7. The analysis code remains K18 and the required distance does not change

Discussion​

ScenarioRelationshipBarricade present?CodeRequired distance
A unbarricadedsamelineNoK18(full)
A barricadedsamelineYesK9(reduced)
B unbarricadedrelatedNoK18(full)
B barricadedrelatedYesK18(full — no change)

The takeaway: a barricade is not a property of a pair of facilities. The reduction it earns is conditional on the operating-line relationship between the PES and the ES. A model that assumes "barricade present = K9" will quietly produce non-conservative results whenever the two facilities turn out to be on parallel lines.

warning

This same rule carries forward into Siter. When you build relationship groups in Siter, the operating-line context determines whether barricading reduces the arcs you see on the map. Adding a barricade feature in Siter will not produce a reduction across parallel operating lines — see Relationship groups.