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153 APPENDIX D Roadside Hazard Rating Category Descriptions The following is an excerpt from Prediction of the Expected · May have guardrail (1.5 to 2 m [5 to 6.5 ft] from pavement Safety Performance of Rural Two-Lane Highways (67), describ- edgeline). ing the distinguishing characteristics of the 7 roadside hazard · May have exposed trees, poles, or other objects (about 3 m rating categories. The final set of photos comes from the or 10 ft from pavement edgeline). FHWA IHSDM website. · Marginally forgiving, but increased chance of a reportable The accident prediction algorithm uses a roadside hazard roadside collision. rating system developed by Zegeer et al. (66) to characterize the accident potential for roadside designs found on two-lane Rating = 5 roads. Roadside hazard is ranked on a seven-point categori- · Clear zone between 1.5 and 3 m (5 to 10 ft) from pavement cal scale from 1 (best) to 7 (worst). The seven categories of edgeline. roadside hazard rating are defined as follows: · Sideslope about 1:3. · May have guardrail (0 to 1.5 m [0 to 5 ft] from pavement Rating = 1 edgeline). · May have rigid obstacles or embankment within 2 to 3 m · Wide clear zones greater than or equal to 9 m (30 ft) from the pavement edgeline. (6.5 to 10 ft) of pavement edgeline. · Virtually nonrecoverable. · Sideslope flatter than 1:4. · Recoverable. Rating = 6 · Clear zone less than or equal to 1.5 m (5 ft). Rating = 2 · Sideslope about 1:2. · Clear zone between 6 and 7.5 m (20 and 25 ft) from pave- · No guardrail. ment edgeline. · Exposed rigid obstacles within 0 to 2 m (0 to 6.5 ft) of the · Sideslope about 1:4. pavement edgeline. · Recoverable. · Non-recoverable. Rating = 3 Rating = 7 · Clear zone about 3 m (10 ft) from pavement edgeline. · Clear zone less than or equal to 1.5 m (5 ft). · Sideslope about 1:3 or 1:4. · Sideslope 1:2 or steeper. · Rough roadside surface. · Cliff or vertical rock cut. · Marginally recoverable. · No guardrail. · Nonrecoverable with high likelihood of severe injuries Rating = 4 from roadside collision. · Clear zone between 1.5 and 3 m (5 to 10 ft) from pavement edgeline. Figures D-1 through D-7 present photographs illustrating · Sideslope about 1:3 or 1:4. the seven roadside hazard rating categories.
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154 Figure D-1. Typical roadway with roadside hazard Figure D-4. Typical roadway with roadside hazard rating equal to 1. rating equal to 4. Figure D-2. Typical roadway with roadside hazard Figure D-5. Typical roadway with roadside hazard rating equal to 2. rating equal to 5. Figure D-3. Typical roadway with roadside hazard Figure D-6. Typical roadway with roadside hazard rating equal to 3. rating equal to 6.
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155 Figure D-7. Typical roadway with roadside hazard rating equal to 7.
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