I have estimated MNL model for mode choice model. I have use disaggregated travel time and aggregated average accessibility time to service by different modes as independent variables in the model. I want to check whether is it okay to include these two variables in the model, since they seems like correlated. However, I checked the correlation of these two variables, these are not correlated. What method should I need to follow to ensure to keep these two variables in the MNL model? I have used Apollo package in R software.