Contractors will resume work at first light to assess the safety of major South Island highways and continue clearing slips to re-open earthquake-closed roads.
The massive 7.5-magnitude quake that struck early on Monday has caused widespread damage, and slips on SH1 have isolated Kaikoura.
The New Zealand Transport Agency says an alternative inland state highway route has been re-established between Picton and Christchurch, via Murchison and Lewis Pass.
Highway manager Neil Walker says some sections will be open to a single lane only and motorists are urged to use caution.
He says a priority for the agency will be undertaking a detailed assessment of the scale and complexity of the large slips on either side of Kaikoura.
NZTA is working with Kaikoura District Council to open the inland road - the old SH70 - between Culverden and Kaikoura.
Mr Walker says SH1 from Picton to Blenheim/Seddon is now open, but Seddon to Cheviot remains closed. Cheviot to Christchurch is open.
He says it is too soon to tell how long it will take to assess the damage on all the upper South Island highways in order to open routes, or open up safe detour routes.
SH7 is open, providing an alternative route for traffic to travel north to Blenheim.
Howver, SH7A, giving access to Hanmer Springs from SH7, will be closed overnight because of risk of further rockfalls.
It will re-open at 7am on Tuesday for light vehicles only and under escort by contractors.