20:42 Jun 23, 2011 

I don't think Chinese language is so scientifically categorical.
Don't 大型巴士 and 小型巴士 use "型" to mean size instead of type?!
Anyway, I don't mean to raise any issue here. After all, language usage is based on habits.
As a matter of fact, all the suggested terms are good and valid. If the context is of general nature, a common term will be good enough. It there is any further concern, perhaps a more specific term may serve better.

08:15 Jun 23, 2011 

我说问题是，size 这里表示尺寸大小。而型没有这个意思，型主要表示形状、结构方面的含义。

23:44 Jun 22, 2011 

The term 全型巴士 is used in some countries especially to describe the size of tourist buses.
It is exactly because of the "half-size bus" that the term is used.
Go search "half-size bus" to see many examples.

05:49 Jun 22, 2011 

什么是全型巴士，难道还有半型巴士不成？

05:29 Jun 22, 2011 

An optional term might be "全型巴士."
Ivan and Wang all have good suggestions. I think it still depends on the context where and how the classification is made (if there is one) .