To use Thunderbird54321's buses on roads you have to make them into track objects. To do this you must open the buses kuid for Edit in Explorer and double click the config.txt file to add this tag:
trackside 0.01
You can place it anywhere in the file then close, save and commit.
To make the bus appear on roads in your route you have to add the bus kuid to your route or to the region kuid used in the route. To do this open the (route or region) kuid for Edit in Explorer and add this tag:
carx <kuid number of bus>
where x is 0 or the next number in sequence if you have a list of cars.
Bob Weber