Why do there appear to be no restrictions against engine compression braking by heavy commercial vehicles in downtown Auckland, in particular those accessing the port via The Strand in Parnell and Beach Rd? Both these areas have council-approved intensive residential areas. If there are controls, why are they not enforced? Keith Watkinson, Auckland

Compression release engine brakes, also known as Jacobs brakes, are the noisiest type of brakes. They are fitted mainly on big American engines such as Detroit, Cummins, Caterpillar and Mack. The system modifies engine valve operation to use engine compression to slow the vehicle. Other large trucks, mainly Japanese and continental models, use exhaust brakes. These are quieter but less efficient and use engine-exhaust back pressure as the braking method.

Auckland Council has never had any controls in place to prohibit the use of engine braking across the city. Because of this, and as long as vehicles comply with existing bylaws and their vehicles are within the manufacturers' specifications, the police can do nothing about the noise.

The council has been working with the freight industry to discourage the use of engine brakes. It does not propose to introduce any changes to the bylaw, as it has no strong evidence that heavy motor vehicle braking is the sole contributor to excessive noise from such vehicles. The slightly better news is that new-generation engine brakes bring with them reduced brake noise.

The motorway that runs through Auckland is part of State Highway 1. Through traffic has to contend with local Auckland traffic.

Advertisement

This might have been okay 10 years back, but no more. Auckland is now the biggest and fastest growing city in terms of population and traffic. Are there any plans to build a bypass road?

I think that should be a priority. Viswanath Vishnubhotla, Auckland.

You may have noticed the construction of the Western Ring Route, connecting Manukau with Albany. Bypassing Auckland city is exactly what this new motorway will do, from next year.

Do you have a question for Phoebe? It can be about transport or any Auckland issue. Email askphoebe@nzherald.co.nz