Public transport works best in moving large volumes of people to or from a single destination in a short period of time, while private motor vehicles work best in moving people to and from dispersed destinations over a long period of time. Each performs poorly at the other function, which is why public transport has a high mode share for peak hour commutes into dense activity centres and cars have a high mode share for off peak trips that start and end in the outer suburbs.
However, this poses a problem when a major arterial road happens to pass through a major centre, resulting in a high proportion of through traffic. This is the worst of both worlds – lots of cars in a dense centre which have an origin and destination that are not well served by public transport. That is where ring roads come in – they allow these roads to bypass these major centres, while car users still reach their destination. This maintains transport to and within the centre focused on public and active transport (walking and cycling).
The most basic ring road is a bypass. Bondi Junction’s Oxford Street used to be its major thoroughfare, resulting in large amounts of traffic passing through it. The construction of the Sydney Enfield Drive re-routed traffic away from Oxford Street, and even allowed the mall to be pedestrianised and limited to buses in certain parts.
A true ring road actually circles around a major centre, such as in Castle Hill. Here the 3 major roads approach Castle Hill and originally converged onto Old Northern Road. A ring road was then set up to circle the Castle Hill Town Centre, with Old Northern Road’s speed limit dropped and more street space designated for pedestrians, on street parking and a bus road. This allowed cafes and restaurants to set up on the street and created a more relaxed environment, compared to the noisy car dominated road that it used to be.
In the case of Parramatta, it’s ring road is now considered too small, and the local council has designated an outer ring road. The inner ring road allowed Church Street (Parramatta’s main North-South high street) to be partly pedestrianised and to become a vibrant cafe, restaurant, and shopping precinct. However, the recent growth in the Parramatta CBD means that this ring road is now too small, and thus resulted in an outer ring road made up of the M4 in the South, the Cumberland Highway in the West, and James Ruse Drive in the North and East. This outer ring road is designed with higher speed limits of around 80km/hour, compared to the 60km/hour in the inner ring road, and thus draws traffic away from even the inner ring road.
The local council is seeking to make improvements to the outer ring road in key pinch points, and its proposal has obtained support from Infrastructure NSW.
A ring road does not even have to go around a centre, and in the case of the Sydney CBD the Cross City Tunnel and Eastern Distributor, which go underneath the city, are also a type of ring road. Together with the Western Distributor, Cahill Expressway, Harbour Bridge, and Harbour Tunnel, these effectively form a ring road, allowing car drivers to go to or from North Sydney, Pyrmont, Kings Cross, or Moore Park without entering a surface street in the CBD.
However, what sets this ring road apart from the other example above is that this is the only case where drivers pay a financial cost for using the ring road, but nothing for going through the CBD. In an ideal world, this situation would be reversed, with access to all parts of these ring roads being free (perhaps with the exception of the Harbour crossings, which cannot be avoided by driving through the CBD) while charging drivers who go through the CBD surface a congestion charge. The new charge could even be used to compensate the private operators of the Cross City Tunnel and Eastern Distributor.
There is actually one more road even better than a ring road – a public and active transport only road. An example of this is the proposed Wentworth Point Bridge that will link Sydney Olympic Park to Rhodes Business Park, but which will only be accessible to buses, bicycles, and pedestrians. Cars will continue to have to make their way the long way around, which has a similar result to a ring road, as it prevents cars from passing through both Sydney Olympic Park and Rhodes Business Park.