The built-in region kuids for TRS2006 are:
Australia,<kuid:-1:7801>
United Kingdom,<kuid:-1:7803>
United States,<kuid:-1:7804>
Germany,<kuid:-1:7808>
You could clone one of those, rename it and add your own list of cars. I cloned one but completely edited its config.txt file using Notepad. The tag ontheright makes it drive on the right. Here is the config.txt file:
kuid <kuid:47907:1118>
trainz-build 2
category-class "YX"
username "Bobs Cars"
kind "region"
region "USA"
watercolor 38,74,92
ontheright 1
defaultjunction 100634
longitude 77,1.2,-1
latitude 38,53.4,1
altitude 0
car0 <kuid:67261:29007>
car1 <kuid:67261:29009>
car2 <kuid:68787:22157>
car3 <kuid:68787:22162>
car4 <kuid:67261:29012>
car5 <kuid:68787:22166>
car6 <kuid:68787:22167>
car7 <kuid:67261:29015>
car8 <kuid:68787:22164>
car9 <kuid:68787:25068>
car10 <kuid:67261:29018>
car11 <kuid:68787:22159>
car12 <kuid:67261:29021>
car13 <kuid:68787:22163>
car14 <kuid:67261:29022>
car15 <kuid:68787:22158>
Bob