earthquake damage has caused landslides, subsidence, and "drop outs" caused by broken water and sewerage lines around Christchurch and canterbury.
At present the emergency authorities are asking people to stay off the roads unless travel is essential. How long this advice will stay in place is unclear.
A state of emergency has been extended in Christchurch until midday Wednesday September 8th, perhaps giving an indication of when officials believe things may return to near normal.
There are a number of road closures around Christchurch (and another at Milford Sound due to flooding, not the quake). You can get updated information on road closures and conditions at this NZ government website: http://www.highwayinfo.govt.nz/
I suggest you keep an eye on the WorldNomads safety page for updates and of course keep checking the news media. about 10 years ago