Complaints to Tauranga City Council about trucks using engine braking on Takitimu Drive are falling on deaf ears.

In spite of an independent consultant's noise level survey showing engine braking noise levels are at objectionable levels, the council can do nothing about the complaints.

Photo: File.

There were 25 submissions on the Draft Traffic and Parking Bylaw 2012, in which the council proposes to remove the current engine braking restrictions on Takitimu Drive and Marsh Street.

In light of the submissions the committee decided to keep the engine braking ban, which councillors pointed out, is meaningless.

Takitimu Drive is now a state highway and under New Zealand Transport Agency jurisdiction. Also, engine braking restrictions only apply where the speed limit is 70km, and the speed limit on Takitimu Drive is 80km/h.

A requirement that the city council enforce an engine braking ban is part of the original coastal permit for the Waikareao Expressway, but Conservation Minister Kate Wilkinson and the BOP Regional Council also failed to take up the residents' complaints.

'As you can imagine on a still night, trucks using Takitimu Drive and that area…the noise is quite dramatic. I certainly wouldn't like to live there,” says Keith Fraser, speaking on behalf of his daughter, who is a Williams Street resident.

'It is the fault of Tauranga City Council and other authorities who have failed to enforce the existing legislation, and now are going to remove that legislation allowing open slather for trucks to use engine brakes on Takitimu Drive.

'It hasn't been enforced in Takitimu Drive and I don't understand why not.

'It's not our road and it's not our bylaw,” says Mayor Stuart Crosby. 'We don't have the authority to enforce a moving violation, that's down to police. The only moving violation we are enforcing is the bus lanes on Hewletts Road.”

Council staff say they would support extending the Hewletts Road 70km/h zone across the bridge to the 50km/h zone north of the Elizabeth Street roundabout. NZTA has undertaken noise monitoring and is investigating options.

The noise level survey carried out in March 2012 by Opus International Consultants found engine braking noise levels at the YHA hostel and at Williams Street - just up the hill - reached 85-90 decibels. The base line average traffic noise level is 65dB.

Engine braking in large diesel motors are a compression release brake. It works by opening the exhaust valves at the top of the compression stroke, resulting in the expansion of the air in the cylinder. The energy stored in that compressed air is not returned to the crankshaft, but released into the atmosphere.

The sudden release of compressed air creates the noise. The engine is then made to pull the piston down sucking new air into the cylinder, and then travel upward again, compressing the new air, which is again released after being compressed.