Pavements & traffic · Traffic & intersections
Road capacity and level of service (multilane / motorway) calculator
Basic motorway or multilane road segment. Demand is converted to passenger cars per hour per lane (peak-hour factor, heavy-vehicle equivalents for the terrain, driver population), free-flow speed is adjusted for lane width and lateral clearance, and the speed–flow curve gives the operating speed, density and level of service A–F, with the volume-to-capacity ratio and the spare capacity.
Standard: HCM 2010 basic freeway / multilane segment (as adopted in Austroads Guide to Traffic Management Part 3) · heavy-vehicle and peak-hour adjustments
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Inputs in the worked example
The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.
| Input | Value | Unit |
|---|---|---|
| Peak-hour volume (one direction) | 3600 | veh/h |
| Lanes in the direction | 2 | |
| Peak-hour factor | 0.92 | |
| Heavy vehicles | 10 | % |
| Terrain | Level (ET = 1.5) | |
| Driver population factor | 1 | |
| Base free-flow speed | 110 | km/h |
| Lane width | 3.5 | m |
| Right-side lateral clearance | 1.8 | m |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Heavy-vehicle factor fHV | 0.952 | |
| Demand flow rate vp | 2,054 | pc/h/ln |
| Free-flow speed | 106.9 | km/h |
| Capacity per lane | 2,364 | pc/h/ln |
| Volume / capacity | 0.87 | |
| Operating speed | 96.0 | km/h |
| Density | 21.4 pc/km/ln (34.4 pc/mi/ln) | |
| Level of service | D | |
| Spare capacity (one direction) | 543 | veh/h |
- ✓ Level of service D or better — LOS D
- ✓ Demand below capacity — 87 %
Method, formulas and assumptions
- vp = V/(PHF·N·fHV·fp), fHV = 1/[1 + PT(ET − 1)].
- FFS = BFFS − fLW − fLC (lane width < 3.6 m and right-side clearance < 1.8 m). Capacity c = 1700 + 10·FFS(mi/h) ≤ 2400 pc/h/ln; speed constant to the breakpoint 1000 + 40(75 − FFS), then falls parabolically to c/45 at capacity.
- LOS by density (pc/mi/ln): A ≤ 11, B ≤ 18, C ≤ 26, D ≤ 35, E ≤ 45, F above or when demand exceeds capacity.
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.