West Coast police today advised motorists to take extra care when driving through the Lewis Pass and Maruia Valley on State highways 7 and 65 as traffic numbers build up.
Greymouth prevention sergeant Paul Watson said road police patrols had been stepped through the area due to "a massive increase" in traffic, diverted via Blenheim and Murchison to Canterbury, as a result of the Kaikoura earthquake.
Other measures were being investigated to deal with the increased traffic flows, with more heavy trucks and freight movements through the Lewis to Christchurch.
"We are looking at working with NZTA to get some temporary speed restrictions in place ... because of the increased traffic flows," Mr Watson said.
The Maruia Valley School was one example where speed restriction measures would be taken.
Drivers also needed to take "a bit more care and caution" by recognising the road conditions and being prepared for the unexpected, given the seismic event had increased instability in some places.
Another deluge of bad weather was also forecast to hit inland and that could exacerbate poor driving conditions or unstable roads, he said.
Meanwhile, post-quake tourists have started flocking to the West Coast, with all main routes open.
"We feel for our friends over the hill, but in the meantime we want to extend a warm West Coast welcome to all tourists and reassure them that we are fully open for business and will give them a fantastic experience in our beautiful region," Tourism West Coast chief executive Jim Little said.
Tourists in Marlborough can drive to the West Coast via the Wairau Valley to Murchison and through the Buller Gorge to Punakaiki or through Reefton to Greymouth.
Those in Canterbury can reach the West Coast via Arthur's Pass or the Lewis Pass, while the Haast Pass is also open.
Mr Little said some tourism operators had bookings affected by Cook Strait ferry cancellations and road closures on the east coast, but then had a surge of unexpected bookings from tourists forced to change their travel plans.