Basic Freeway Segments
Estimate free-flow speed, capacity, density, and level of service for a basic freeway segment in the analysis direction.
Analysis Method
The Chapter 12 method converts heavy vehicles to passenger cars and reads speed and density in passenger-car units. Where the grade is steep enough or the truck share high enough that the passenger-car equivalents no longer hold, the Chapter 25 and 26 mixed-flow model works the truck stream directly and reports speed and density in vehicle units instead.
Outputs
The HCM Chapter 12 operational chain, step by step. Results populate after pressing Calculate.
| Step | Quantity | Value |
|---|---|---|
| 1 | Free-flow speed, FFS | — |
| 2 | Base capacity | — |
| Adjusted capacity | — | |
| 3 | Passenger-car equivalent, ET | — |
| Heavy-vehicle factor, fHV | — | |
| 4 | Demand flow rate, vp | — |
| 5 | Space mean speed, S | — |
| Volume-to-capacity ratio, v/c | — | |
| 6 | Density, D | — |
| 7 | Level of service | — |
Density and LOS follow HCM Exhibit 12-15. ET is read from the general-terrain exhibit (12-25).