here is some quote from IGN
Oh, but that's not where the problems with traffic end. One of the game's bigger technical issues is that while the framerate largely stays steady, the draw distance suffers greatly for it, especially with regards to the barren traffic. Cars in the distance will first appear simply as shadows, and as you close in, the cars will magically appear out of the Netherworld right in front of you. I'm not talking about a quarter-mile down the road, but more on the order of 200 feet. At high speeds, this doesn't leave you much time to react, though at least there isn't much traffic to contend with. Sigh.
Need for Speed Undercover is not a good game by any stretch of the definition. It has numerous technical problems, including cars that don't appear until you get close to them and a poor enough overall visual quality that it can be hard to make out the track. The open world setting is misused as many races are closed off, and the driving mechanics on the whole are uninspired.
like i said, i played this game with the original disc i borrowed from my buddy..
and it was a shitty car (because i was playing for not more than 2 hours) and in one occasion i was able to outrun the draw distance (with a shitty ass car) and it just resetted my car.
at that moment i said to myself, ok that's enough, fuck this shit... then never played the game again.