Two-Way Stop-Controlled (TWSC) Calculator

Follows Chapter 32 Example 1 from the 2022 HCM: three-leg TWSC with a stop-controlled minor approach.

Analysis settings

Analysis period (hours)

Heavy vehicles (% of approach flow)

Approach grade (%)

Grade and heavy vehicles feed into the critical/follow-up headway adjustments. Use the heavy-vehicle percent for the approach you are analyzing (major LT uses major %, minor LT/RT use minor %). Use the grade on that same approach; set to 0 for level.

Volumes

Enter either peak 15-min counts or hourly flows. Choose below and the tool will handle the conversion.

Lane configuration diagram — Match your movements to the v-numbers shown.

Your inputs are:

EB = eastbound major, WB = westbound major, NB = stop-controlled minor. Enter counts for your analysis approach.

EB (major)

EB through (v2)

EB right (v3)

EB left (v1, optional)

EB U-turn (v1U, optional)

WB (major)

WB through (v5)

WB left (v4)

WB right (v6)

WB U-turn (v4U, optional)

NB (minor stop)

Minor left (v7)

Minor right (v9)

Other conflicts

Other conflicting (v13)

Other conflicting (v14)

Other conflicting (v15)

Optional fields default to 0, matching the Example 1 geometry. Adjust only if your site has those conflicts.

References

Steps and coefficients follow HCM 2022 Chapter 32 supplemental example (Version 7.0, July 2022).