(a) Regression models developed for safety edge treatment (Model 1) | ||||||||
Model variables | All crash type | Lane-departure crashes | ||||||
Fatal and injury | All crashes | Fatal and injury | All crashes | |||||
Parameter Estimates | Standard Error (p-value) | Parameter Estimates | Standard Error (p-value) | Parameter Estimates | Standard Error (p-value) | Parameter Estimates | Standard Error (p-value) | |
Intercept | −8.901 | 3.4037 (0.0089) | −8.176 | 4.3537 (0.0604) | 18.216 | 30.5747 (0.5513) | −16.039 | 7.409 (0.0304) |
Safety edge | −0.243 | 0.1521 (0.1103) | −0.261 | 0.2904 (0.3692) | −0.154 | 0.2934 (0.6004) | −0.277 | 0.3023 (0.3593) |
Segment Length | 0.333 | 0.0586 (<0.0001) | 0.319 | 0.1062 (0.0026) | 0.223 | 0.0949 (0.0186) | 0.336 | 0.1045 (0.0013) |
Posted speed limit | 4.285 | 1.359 (0.0016) | 0.007 | 0.0035 (0.0569) | 0.521 | 2.1276 (0.8064) | 5.286 | 3.4684 (0.1275) |
AADT | 2.031 | 0.4064 (<0.0001) | 2.210 | 0.8797 (0.012) | 0.270 | 0.6846 (0.6929) | 2.052 | 0.8257 (0.013) |
Average lane width | 0.093 | 0.0982 (0.3418) | 0.288 | 0.195 (0.14) | 0.217 | 0.0914 (0.0178) | 0.301 | 0.1704 (0.0774) |
Dispersion | 0.375 | 0.590 |
| 0.352 | 0.278 | |||
(b) Regression models developed for adding 2 ft paved shoulders with rumble strips (Model 2) | ||||||||
| All crash type | Lane-departure crashes | ||||||
| All crashes | Fatal and injury | All crashes |
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Parameter | Parameter Estimates | Standard Error (p-value) | Parameter Estimates | Standard Error (p-value) | Parameter Estimates | Standard Error (p-value) | Parameter Estimates | Standard Error (p-value) |
Intercept | 0.251 | 0.3134 (0.4240) | −0.196 | 0.3980 (0.6232) | 0.238 | 0.3207 (0.4573) | -3.337 | 2.2393 (0.1362) |
Segment length | 0.667 | 0.0712 (<0.0001) | 0.529 | 0.0742 (<0.0001) | −0.002 | 0.0018 (0.3412) | 0.008 | 0.0074 (0.3017) |
AADT | 0.158 | 0.0441 (0.0003) | 0.183 | 0.0492 (0.0002) | −0.073 | 0.0497 (0.1399) | 0.071 | 0.0682 (0.3011) |
Asphalt Resurfacing | −0.920 | 0.1661 (<0.0001) | −0.947 | 0.2356 (<0.0001) | 0.237 | 0.1526 (0.1209) | 0.308 | 0.2049 (0.1334) |
Only 2 ft shoulders | 0.256 | 0.1199 (0.0326) | 0.102 | 0.1413 (0.4709) | −0.320 | 0.1388 (0.0214) | −0.313 | 0.186 (0.0922) |
2 ft shoulders with rumble strips | −0.294 | 0.1365 (0.0311) | −0.661 | 0.1951 (0.0007) | −0.267 | 0.1501 (0.0758) | −0.623 | 0.2435 (0.0105) |
Dispersion | 2.347 | 2.087 | 2.336 | 1.921 |