Roadway Geometric Design: sag_vertical_curve
AASHTO Green Book 7th Edition (2018) roadway geometric design standards — stopping sight distance (15–80 mph), passing sight distance (20–70 mph), minimum horizontal curve radius by design speed and emax (4%/6%/8%), K-values for crest and sag vertical curves (25–80 mph), maximum grade limits by terrain type (level/rolling/mountainous) and road class (freeway/arterial/collector/local), superelevation standards, lane and shoulder width standards, and design vehicle dimensions (P, SU, WB-40, WB-62, WB-67).
| parameter type | record id | description | design speed mph (mph) | notes | unit | value min (varies) | value typical (varies) |
|---|---|---|---|---|---|---|---|
| sag_vertical_curve | k_sag_25 | Sag vertical curve K-value — 25 mph | 25 | K based on headlight sight distance; comfort criterion governs at sag curves; h1=2.0ft headlight ht, 1-degree upward beam divergence | ft/% | 26 | 26 |
| sag_vertical_curve | k_sag_30 | Sag vertical curve K-value — 30 mph | 30 | K=37; per AASHTO 2018 Table 3-36 | ft/% | 37 | 37 |
| sag_vertical_curve | k_sag_35 | Sag vertical curve K-value — 35 mph | 35 | K=49 | ft/% | 49 | 49 |
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