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

Table 12

Comparison of determinants in IAC and NIAC.

Variable	IAC	NIAC	Detailed information
Driver characteristics
Improper action	—	2017	Temporal instability and nontransferability
Vehicle characteristics
Single-vehicle indicator	—	2017/2018/2019	Nontransferability
Two-vehicle indicator	—	2017	Temporal instability and nontransferability
Multivehicle indicator	2017/2018	2017/2018	Temporal instability, this variable increases higher likelihood of severe injuries in IAC models than in NIAC models
Minibus	—	2019	Temporal instability and nontransferability
Bus	—	2018	Temporal instability and nontransferability
Van	—	2018	Temporal instability and nontransferability
Truck	2018	2017	Temporal instability and nontransferability
Heavy truck	—	2018	Temporal instability and nontransferability
Roadway characteristics
	2018	—	Temporal instability and nontransferability
	—	2018/2019	Temporal instability and nontransferability
	—	2019	Temporal instability and nontransferability
	—	2017/2018	Temporal instability and nontransferability
Environmental characteristics
Sunny	—	2017	Temporal instability and nontransferability
Cloudy	—	2018	Temporal instability and nontransferability
Rainy	—	2019	Temporal instability and nontransferability
Snowy	—	2018	Temporal instability and nontransferability
Icy road	2019	—	Temporal instability and nontransferability
Temporal characteristics
Monday	—	2018	Temporal instability and nontransferability
Tuesday	2018/2019	—	Temporal instability and nontransferability
Wednesday	—	2017/2018/2019	Nontransferability
Early morning	2017/2018/2019	2018	Temporal instability. The effect on severe injuries in the early morning time in the 2019 NIAC model is almost 10 times higher than that in the 2018 IAC model
Afternoon	—	2017/2018	Temporal instability and nontransferability
Night	2017/2018	2017/2018	Temporal instability. The effects on severe injuries in the NIAC model are significantly higher than those in the IAC model
Spring	—	2017/2019	Temporal instability and nontransferability
Summer	—	2019	Temporal instability and nontransferability
Winter	2017/2019	2017/2018	Temporal instability
Traffic characteristics
AADT	2017/2018/2019	2017/2018/2019	Temporal stability and transferability
Crash characteristics
Sideswipe	—	2017/2019	Temporal instability and nontransferability
Hit fixed object	—	2017	Temporal instability and nontransferability
Rear-end collision	—	2019	Temporal instability and nontransferability
Other crash types	2018	2017	Temporal instability and nontransferability
EMS greater than 60 minutes	—	2018	Temporal instability and nontransferability