塞
塞 – Sai1 – Block, Clog, Stuff, Squeeze In
塞車 – Sai1 Che1 – Clog Car — Traffic Jam (in Taiwan!)
堵車 – Du3 Che1 – Stop Up Car — Traffic Jam (in China!)
This is one of those things that is said differently in China and Taiwan. I don’t think I know enough to characterize how different Mandarin as spoken in China and Taiwan is. I get the sense that they’re pretty different, maybe even as different as British English and American English.