Random-effects ordered probit model - intraclass correlation

I am using mixor package in R (https://www.rdocumentation.org/packages/mixor/versions/1.0.4/topics/mixor) to explore influential factors on injury severity among crash-related, road-related and etc factors. it has assumed that shared variance among individuals involved in the same crash is high, so random-effects ordered probit model is utilized.

My question is how I can calculate intraclass correlation among individuals in the same crash to justify why i choose random-effects model