Canterbury's Highway Patrol is reminding motorists to drive with caution while the Lewis Pass alternate highway (State Highway 7) remains the main route between Picton and Christchurch.
The Lewis Pass/ Murchison alternate highway is likely to remain the only highway for some time, while the New Zealand Transport Agency (NZTA) continue to clear slips generated by the Kaikoura earthquakes.
Canterbury's Highway Patrol team leader Senior Sergeant Philip Dean said neither police nor NZTA can manage the issue alone.
"Road safety is everyone's responsibility and unsafe driving on this road is putting all road users at risk," he said.
"I've driven the Murchison highway route many times and every day I see motorists attempting to overtake other drivers.
"The risk is fruitless."
Anyone who attempts to overtake a truck, campervan or another slow-moving vehicle on the route will only be held up by another slow-moving vehicle further down the road.
"The best advice is to be patient and accept that your journey on this route will take longer than it did on SH1."
Dean reminded road users the route would take much longer than people are anticipating.
"The route, which is more challenging than State Highway 1, takes at least seven and a half hours, but motorists should prepare for it to take longer.
"There are plenty of places to stop for a significant break or rest, including Springs Junction, Amberley, Culverden, Murchison and Hanmer Springs.
"Fatigue is deadly on the road.
"It's also easily avoidable with the right planning, regular breaks and a good night's sleep."
There will be increased police patrols throughout the route.
To report non urgent road-related matters call *555.
Works are planned on the Lewis Pass alternate state highway route in coming days and weeks to ensure it is resilient and able to carry the increased traffic volumes safely over the busy summer period.
The Transport Agency will be increasing the areas available for trucks to park in small towns leaving more space on the roadside for other traffic. They will also soon be upgrading the road marking and enhancing other safety features, like signage.
This is expected to start in the next fortnight.
A programme of improved safety works will follow including road widening at critical points to help vehicles travel safely in each direction.
Meanwhile, construction of additional slow vehicle bays will enable faster vehicles to pass safely while slow vehicles pull over.
NZTA has more crews on the network than ever before to ensure any potholes that develop, or any other defect, is repaired promptly.
The agency is also increasing the technology on the network in line with what normally occurs on the State Highway 1 system.