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EVALUATION OF ZERO-LENGTH VERTICAL CURVES.
| 题名： | EVALUATION OF ZERO-LENGTH VERTICAL CURVES. |
| 作者： | Wooldridge-MD; Nowlin-RL; Parham-AH |
| 关键词： | DESIGN-SPEED; HIGHWAY-DESIGN; HIGHWAY-GRADES; HIGHWAY-PROFILE; SIGHT-DISTANCE; VERTICAL-ACCELERATION; VERTICAL-CURVES |
| 摘要： | To evaluate the use of zero-length vertical curves with respect to Texas Department of Transportation design practice, construction results, and vehicle dynamics, and to compare zero-length vertical curves with minimum-length design vertical curves, 20 zero-length vertical curves and 15 minimum-length vertical curves were evaluated. Evaluations performed included examinations of sight distance for zero-length vertical curves, surveying roadway profiles, and measuring vertical accelerations. Sight distance criteria were found to be generally inapplicable below 2 percent for sag vertical curves. For crest vertical curves, sight distance criteria were inapplicable below 1 percent for design speeds of 90 km/h or less and inapplicable below 0.5 percent for design speeds of 100 to 120 km/h. The results of vertical acceleration testing showed that, below 0.5 percent grade change, no practical difference was found between zero-length and minimum-design-length vertical curves. Between 1.0 and 0.5 percent grade change, significantly higher accelerations were measured for high-speed tests on zero-length vertical curves. Finally, it was found that zero-length vertical curves were more likely to meet drainage grade requirements than minimum-design-length vertical curves were. |
| 总页数： | Transportation Research Record. 1999. (1658) pp52-59 (1 Phot., 4 Fig., 2 Tab., 7 Ref.) |
| 报告类型： | 科技报告 |
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