Questions & Answers about U centru je veliki saobraćaj svako jutro.
Because u can take two different cases:
- accusative for movement to/into somewhere: u centar = to the center
- locative for being in a place: u centru = in the center
In this sentence, there is no movement. It describes where the traffic is, so Serbian uses the locative: u centru.
Centru is the locative singular of centar.
The noun changes like this:
- nominative: centar
- locative: centru
After u when it means in, the locative is used, so u centru means in the center / downtown.
This is a normal Serbian way to say that something is present somewhere.
Literally, the structure is close to:
- U centru je veliki saobraćaj.
- In the center is heavy traffic.
English usually prefers There is heavy traffic downtown, but Serbian can simply use je with the noun phrase.
So je agrees with saobraćaj, which is singular.