Journal of Advanced Transportation

Research Article

Do Expressway Interchanges Increase Crash Injury Severities? Insights Using Temporal Instability and Unobserved Heterogeneity

Table 2

Descriptive statistics (standard deviation in parentheses) of significant variables in IAC and NIAC across 2017 to 2019.
Variable201720182019
IACNIACIACNIACIACNIAC
Driver characteristics
Safety (1 if speeding, 0 otherwise)0.820 (0.379)0.734 (0.442)0.880 (0.325)0.690 (0.462)0.481 (0.500)0.422 (0.494)
Safety (1 if improper action, 0 otherwise)0.126 (0.241)0.238 (0.426)0.120 (0.325)0.305 (0.461)0.516 (0.500)0.577 (0.494)
Vehicle characteristics
Vehicle indicator (1 if the number of vehicles involved in the crash is 1, 0 otherwise)0.503 (0.499)0.619 (0.486)0.389 (0.488)0.470 (0.499)0.222 (0.415)0.453 (0.498)
Vehicle indicator (1 if the number of vehicles involved in the crash is 2, 0 otherwise)0.425 (0.496)0.328 (0.470)0.526 (0.500)0.448 (0.497)0.655 (0.476)0.466 (0.499)
Vehicle indicator (1 if the number of vehicles involved in the crash is > 2, 0 otherwise)0.072 (0.315)0.053 (0.224)0.086 (0.280)0.082 (0.274)0.123 (0.329)0.082 (0.274)
Vehicle type (1 if passenger car, 0 otherwise)0.353 (0.522)0.326 (0.516)0.350 (0.478)0.384 (0.509)0.326 (0.454)0.365 (0.514)
Vehicle type (1 if minibus, 0 otherwise)0.372 (0.582)0.380 (0.596)0.411 (0.670)0.504 (0.565)0.444 (0.506)0.352 (0.350)
Vehicle type (1 if bus, 0 otherwise)0.123 (0.325)0.009 (0.096)0.057 (0.232)0.029 (0.169)0.003 (0.056)0.016 (0.125)
Vehicle type (1 if van, 0 otherwise)0.037 (0.168)0.002 (0.041)0.017 (0.130)0.013 (0.113)0.009 (0.097)0.006 (0.074)
Vehicle type (1 if truck, 0 otherwise)0.125 (0.241)0.051 (0.221)0.137 (0.344)0.182 (0.386)0.481 (0.500)0.471 (0.499)
Vehicle type (1 if heavy truck, 0 otherwise)0.090 (0.189)0.047 (0.212)0.360 (0.480)0.256 (0.436)0.009 (0.097)0.025 (0.156)
Roadway characteristics
: radius of the plane curve of front section (103 m)227.067 (442.562)457.565 (494.325)220.402 (316.263)481.521 (495.938)280.408 (443.770)424.397 (490.117)
: radius of the horizontal curve (103 m)476.616 (497.219)326.923 (464.013)517.533 (496.929)332.438 (466.003)431.369 (491.346)389.388 (483.171)
radius of the plane curve of back section (103 m)286.600 (476.896)464.218 (494.944)334.140 (417.280)470.771 (495.394)353.047 (418.818)343.797 (425.888)
: length of the plane curve of front section (103 m)0.943 (0.734)1.248 (0.711)0.770 (0.469)1.276 (0.727)1.394 (0.756)1.448 (0.705)
: length of the horizontal curve (103 m)1.356 (0.589)1.631 (0.657)1.312 (0.551)1.671 (0.608)1.291 (0.689)1.449 (0.759)
: length of the plane curve of back section (103 m)0.906 (0.622)1.269 (0.757)0.801 (0.486)1.257 (0.747)1.234 (0.712)1.449 (0.759)
: minimum longitudinal grade of current section (%)0.011 (0.486)0.107 (3.219)0.039 (0.557)0.018 (0.432)0.014 (0.428)0.021 (0.415)
: length of the longitudinal slope corresponding to the minimum grade (m)675.024 (274.427)750.991 (274.959)669.874 (250.212)747.066 (277.276)711.898 (322.849)354.359 (396.518)
: maximum longitudinal grade of current section (%)0.034 (1.215)0.103 (1.422)0.072 (1.206)0.062 (1.100)0.075 (1.034)0.078 (1.205)
: length of the longitudinal slope corresponding to the maximum grade (m)644.096 (244.602)619.512 (237.251)648.509 (146.288)605.182 (225.170)481.942 (156.365)523.322 (40.203)
Environmental characteristics
Weather (1 if fine, 0 otherwise)0.324 (0.375)0.329 (0.381)0.193 (0.338)0.124 (0.330)0.272 (0.445)0.273 (0.445)
Weather (1 if cloudy, 0 otherwise)0.383 (0.399)0.337 (0.425)0.331 (0.471)0.379 (0.485)0.658 (0.475)0.585 (0.493)
Weather (1 if rainy, 0 otherwise)0.174 (0.458)0.250 (0.409)0.326 (0.469)0.361 (0.480)0.051 (0.219)0.085 (0.279)
Weather (1 if foggy, 0 otherwise)0.054 (0.299)0.023 (0.149)0.097 (0.296)0.042 (0.201)0.009 (0.097)0.026 (0.159)
Weather (1 if snowy, 0 otherwise)0.054 (0.156)0.061 (0.239)0.051 (0.221)0.068 (0.252)0.016 (0.125)0.036 (0.187)
Road surface condition (1 if icy, 0 otherwise)0.012 (0.111)0.019 (0.138)0.017 (0.130)0.034 (0.181)0.015 (0.180)0.016 (0.131)
Temporal characteristics
Monday (1: occurs on Monday, otherwise 0)0.138 (0.368)0.113 (0.317)0.080 (0.272)0.116 (0.320)0.098 (0.298)0.122 (0.327)
Tuesday (1: occurs on Tuesday, otherwise 0)0.126 (0.330)0.118 (0.323)0.103 (0.304)0.110 (0.313)0.146 (0.353)0.136 (0.343)
Wednesday (1: occurs on Wednesday, otherwise 0)0.162 (0.379)0.138 (0.345)0.183 (0.387)0.129 (0.335)0.130 (0.336)0.119 (0.324)
Thursday (1: occurs on Thursday, otherwise 0)0.198 (0.330)0.167 (0.373)0.183 (0.387)0.180 (0.384)0.161 (0.368)0.137 (0.344)
Friday (1: occurs on Friday, otherwise 0)0.120 (0.343)0.155 (0.362)0.149 (0.356)0.172 (0.377)0.165 (0.371)0.171 (0.376)
Saturday (1: occurs on Saturday, otherwise 0)0.144 (0.330)0.178 (0.382)0.131 (0.338)0.156 (0.363)0.171 (0.377)0.186 (0.390)
Sunday (1: occurs on Sunday, otherwise 0)0.114 (0.368)0.131 (0.337)0.171 (0.377)0.138 (0.345)0.130 (0.336)0.129 (0.335)
Early morning (1: occurs from 00 : 00 to 05 : 59, otherwise 0)0.467 (0.498)0.485 (0.500)0.211 (0.409)0.247 (0.431)0.310 (0.463)0.276 (0.447)
Morning (1: occurs from 6 : 00 to 11 : 59, otherwise 0)0.198 (0.389)0.180 (0.384)0.349 (0.477)0.278 (0.448)0.212 (0.409)0.248 (0.432)
Afternoon (1: occurs from 12 : 00 to 17 : 59, otherwise 0)0.198 (0.399)0.216 (0.411)0.246 (0.431)0.290 (0.454)0.288 (0.453)0.295 (0.456)
Evening (1: occurs from 18 : 00 to 23 : 59, otherwise 0)0.138 (0.379)0.120 (0.325)0.194 (0.396)0.185 (0.389)0.190 (0.392)0.182 (0.386)
Spring (1: occurs in spring, otherwise, 0)0.246 (0.262)0.266 (0.442)0.440 (0.497)0.346 (0.476)0.320 (0.365)0.207 (0.405)
Summer (1: occurs in summer, otherwise, 0)0.246 (0.472)0.219 (0.414)0.234 (0.424)0.213 (0.410)0.263 (0.244)0.284 (0.348)
Autumn (1: occurs in autumn, otherwise, 0)0.281 (0.468)0.277 (0.448)0.200 (0.400)0.254 (0.435)0.279 (0.270)0.305 (0.317)
Winter (1: occurs in winter, otherwise, 0)0.228 (0.446)0.237 (0.425)0.126 (0.332)0.188 (0.390)0.138 (0.191)0.204 (0.315)
Traffic characteristics
Bridge (1: the section occurring is the bridge section, otherwise 0)0.305 (0.439)0.287 (0.452)0.269 (0.444)0.278 (0.448)0.244 (0.430)0.267 (0.443)
AADT: Average annual daily traffic volume45634.6 (9917.2)52156.030 (11215.396)45110.6 (9096.3)53365.1 (10855.6)50261.0 (11469.3)52496.4 (10851.5)
Crash characteristics
Sideswipe (1: the crash type is sideswipe, otherwise 0)0.006 (0.111)0.004 (0.065)0.011 (0.106)0.020 (0.140)0.013 (0.112)0.014 (0.117)
Run-off-road (1: the crash type is run-off-road, otherwise 0)0.036 (0.111)0.056 (0.231)0.057 (0.232)0.055 (0.229)0.028 (0.166)0.063 (0.243)
Overturned (1: the crash type is overturned, otherwise 0)0.012 (0.156)0.002 (0.041)0.000 (0.000)0.002 (0.046)0.000 (0.000)0.000 (0.000)
Hit fixed object (1: the crash type is hit fixed object, otherwise 0)0.275 (0.299)0.281 (0.449)0.269 (0.444)0.324 (0.468)0.255 (0.362)0.311 (0.463)
Rear-end (1: the crash type is rear-end, otherwise 0)0.401 (0.477)0.264 (0.441)0.362 (0.461)0.304 (0.492)0.350 (0.433)0.493 (0.500)
Other crash types (1: other crash types, otherwise 0)0.269 (0.500)0.393 (0.488)0.301 (0.452)0.298 (0.490)0.360 (0.438)0.125 (0.331)
Crash indicator (1 if flat-tire, 0 otherwise)0.006 (0.111)0.006 (0.077)0.000 (0.000)0.000 (0.000)0.003 (0.056)0.001 (0.030)
Crash indicator (1 if mechanical fault, 0 otherwise)0.000 (0.000)0.002 (0.041)0.000 (0.000)0.002 (0.046)0.000 (0.000)0.000 (0.000)
EMS shorter than 20 minutes (1: rescue response time is shorter than 20 minutes, otherwise 0)0.048 (0.189)0.055 (0.228)0.034 (0.182)0.038 (0.191)0.006 (0.079)0.020 (0.141)
EMS among 20–60 minutes (1: rescue response time is 20–60 minutes, otherwise 0)0.557 (0.501)0.564 (0.496)0.600 (0.490)0.544 (0.498)0.152 (0.359)0.264 (0.441)
EMS greater than 60 minutes (1: rescue response time greater than 60 minutes, otherwise 0)0.395 (0.500)0.381 (0.486)0.366 (0.482)0.418 (0.493)0.842 (0.365)0.715 (0.451)