A motorist in a rental vehicle has been pulled over and fined for driving too slowly.

Included in the 40-long queue of cars built up behind the vehicle was an off-duty police officer.

Sergeant Alex Pickover, who was on a day off, said the vehicle was travelling 50km/h in a 100km/h zone on the Christchurch-Akaroa Rd on Saturday.

Another on-duty police officer pulled the vehicle up.

"There were quite a few backed up behind it before police pulled the vehicle over. It was quite a hold-up for a number of motorists," he said.

Meanwhile, on Tuesday, police received a complaint about a vehicle speeding towards Christchurch on Main South Rd (State Highway 1).

Police clocked the vehicle at 141km/h between Rolleston and Dunsandel and the woman had her licence suspended for 28 days on the spot and her car was impounded.