Roadway Geometric Design: horizontal_curve_emax8
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) |
|---|---|---|---|---|---|---|---|
| horizontal_curve_emax8 | hc_e8_30 | Min horizontal curve radius — 30 mph emax 8% | 30 | Rmin = V^2/[15*(emax/100 + f_s)]; f_s=0.28 at 30mph; emax=8%; per AASHTO 2018 Table 3-7 | ft | 250 | 250 |
| horizontal_curve_emax8 | hc_e8_40 | Min horizontal curve radius — 40 mph emax 8% | 40 | Rmin emax=8%, f_s=0.23 at 40 mph; per AASHTO 2018 Table 3-7 | ft | 510 | 510 |
| horizontal_curve_emax8 | hc_e8_50 | Min horizontal curve radius — 50 mph emax 8% | 50 | Rmin emax=8%, f_s=0.19 at 50 mph; per AASHTO 2018 Table 3-7 | ft | 930 | 930 |
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