Roadway Geometric Design: passing_sight_distance
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) |
|---|---|---|---|---|---|---|---|
| passing_sight_distance | psd_20 | Passing sight distance — 20 mph design speed | 20 | Minimum PSD for two-lane highway passing maneuver; eye ht 3.5ft, object ht 3.5ft | ft | 400 | 400 |
| passing_sight_distance | psd_25 | Passing sight distance — 25 mph design speed | 25 | Per AASHTO 2018 Table 3-3 | ft | 450 | 450 |
| passing_sight_distance | psd_30 | Passing sight distance — 30 mph design speed | 30 | Per AASHTO 2018 Table 3-3 | ft | 500 | 500 |
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