The City Walls – Matt Olsen

Motorways/Highways are a feature of most major cities in some shape or form. They act as a vein/artery system allowing vehicular tranport en masse into, out of, and around cities at high speeds. Particularly in geographically sparse locations such as the Auckland Isthmus, motorways almost exclusively (save from ferry’s and trains) facilitate the multitudes who commute from (and to) suburbs and satellite towns as seperated as Rodney and the Bombay Hills.

Motorways tend not to be an afterthought in the process of urban planning/buildup, or at least, it would be difficult to construct an effective motorway system where the planning scheme had not already allowed the necessary space for one, without a great deal of destruction/clearing involved. Such was the case in Auckland around the Central Motorway Junction, where suburbs were pulled apart and streets foreshortened for this large imposition.

One consequence of the carrying capacity and high speed of motorways manifests in their distinctive ‘bezier’ shape. To allow safe turning angles and traffic separation around corners the motorway as a path must approach and veer towards its destination with gentle, wide reaching curves, far removed from inner city areas where a ‘shortest distance between two points is a straight line’/grid method is prevalent, and is most efficient to build around, creating an easily definable system of streets. The bezier motorway, in contrast to the city grid, creates no such street edges, onramps and offramps which inject traffic into/diffuse traffic out from the motoway must be set back to allow a safe speeding up/slowing down of traffic as they exit/enter the urban grids neighbouring.