A total of 71 offences were recorded in a joint enforcement blitz in the northern part of Singapore on Wednesday to crack down on errant vehicle-related issues like excessive smoke and noise emission, illegal modifications, and speeding.

Visible smoke emission garnered the highest number of offences: 46 diesel vehicles were caught and fined up to $500 for smoke levels exceeding 50 Hartridge smoke units (HSU).

The three-and-a-half-hour-long blitz, which began at 3 pm, was conducted by the National Environment Agency (NEA), the Land Transport Authority (LTA), and the Traffic Police.

Some 40 officers from the three agencies operated out of a heavy vehicle carpark at Marsiling Crescent, where stations to test for smoke emission levels and noise levels had been set up.

Outriders from the agencies took to the roads, covering a 10-km radius around the carpark in order to identify problematic vehicles and escort them back to the carpark for checks.

Those caught speeding by the Traffic Police were fined on the spot, while vehicles directed to the carpark were checked for smoke emission levels and illegal modifications, such as tinted windows or modified exhaust pipes that generate excessive noise.

The joint blitz comes after an increase in the number of smoky and noisy vehicles caught on roads here this year.

NEA said there were 5,809 cases against vehicles with high smoke emissions between January and September this year. For the whole of last year, the figure was 6,381 while for 2011, it was 4,794.

Tighter rules to limit diesel emissions will kick in next year, as part of NEA's efforts to improve air quality standards in Singapore.

From Jan 1, all diesel vehicles must achieve a smoke opacity test result of 40 HSU or lower when they go for compulsory vehicle inspections to renew their road tax.

Currently, vehicles are allowed to clock in smoke emissions of up to 50 HSU.