Roadway Geometric Design: crest_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) |
|---|---|---|---|---|---|---|---|
| crest_vertical_curve | k_crest_25 | Crest vertical curve K-value — 25 mph | 25 | K = SSD^2/[200*(sqrt(h1)+sqrt(h2))^2]; h1=3.5ft h2=2.0ft; L=K*A; L=curve length(ft), A=grade change(%); minimum value | ft/% | 12 | 12 |
| crest_vertical_curve | k_crest_30 | Crest vertical curve K-value — 30 mph | 30 | K=19; SSD=200ft; per AASHTO 2018 Table 3-34 | ft/% | 19 | 19 |
| crest_vertical_curve | k_crest_35 | Crest vertical curve K-value — 35 mph | 35 | K=29; SSD=250ft | ft/% | 29 | 29 |
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