Police are cracking down on dangerous drivers travelling along the inland route from Picton to Christchurch.
The clampdown follows a fatal crash on Wednesday, just north of Springs Junction.
Hundreds of truck drivers are among extra vehicles forced to take the detour as a result of the Kaikoura earthquakes.
There are 14 extra police cars on the road to deal with the heavier load, and one driver was stopped twice for speeding in a matter of minutes.
Police officer Al Stewart said the speeding comes when drivers get frustrated with the detour.
"It's just that urgency to try and make up that time that they feel they're losing the extra two and a half hours," he said. "It's just about planning your trip."
Since the earthquake, police have handed out around 160 speeding tickets along the stretch of road.
Ten of those were caught travelling so fast over the speed limit they immediately lost their licence.