The subject NP which designates the place where an action happens or a state obtains requires the locative semantic role; the subject NP which designates the time of an action or a state requires the temporal semantic role:
Lúndūn duō wù.
(London is foggy.)
Wǒ de zhàngpeng shuì de xià sān gèrén.
(My tent can sleep three people.)
Lùshang mǎ nshì zìxíngchē hé xíngrén.
(The road is swarmed with bicycles and pedestrians.)
Xiāngzi lǐ zhuāngmǎn le shū.
(The box is packed with books.)
Wǔyuè yīhào shì Láodòngjié.
(May the First is Labor Day.)
In the above sentences, all the subjects denote the location where the states described by the predicates apply. In (1c), for instance, the state of being full of bicycles and pedestrians obtains on the road. So the subject has the semantic role of location. The subject of (1e) designates the date on which it is Labor Day; hence the subject is assigned the semantic role of time.
 Loar, J. K. (2011). Chinese syntactic grammar: functional and conceptual principles. New York: Peter Lang.