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

Table 4

Likelihood ratio test results of NIAC in different years.

2017	2018	2019
2017	—	72.68 (22) [>99.99%]	96.26 (15) [>99.99%]
2018	94.25 (20) [>99.99%]	—	85.19 (15) [>99.99%]
2019	79.62 (20) [>99.99%]	109.22 (22) [>99.99%]	—

Note. () is the degree of freedom of the model; [] is the confidence level.