Hello ,
I want suggest a complement, for the RHW (URHW = Underground RHW) .
At this time , this tube existes for the Flup :

With LHD and RHD , I think that is good if there are elements with green light in right and left (only an idea).
To complete this collection of elements, I propose this parts :
Tube entrance :

Underground RHW in 2x2 :
transition between tunnel and half underground.

transition with a aerial round about :

sample transition with aerial way :

undercover way in underground for a center of round about :

part of underground connection :

My skill with BAT are limited . I own Gmax , BAT and SC4PIMX. I'm don't know the system with program to transform a lot / model in TE (transit enable).
I can in first time product a lot in cosmetic or eyes candies.