Interesting travel stuff

I clipped this from a NSW Parliament research paper.

However, work by Marchetti in 1992 demonstrated that the time people are prepared to spend travelling to and from work has remained remarkably unvaried throughout settlement history. Now known as the Marchetti constant, it is an essentially constant travel time budget of, on average, 30 minutes commuting either way between residence and workplace.

Hence the size of the city has been influenced by the distance which can be travelled within that time budget. An increase in travel speed has been provided by new technology, and this has facilitated an increase in urban scale, with transition from walking city to transit city to automobile city to (in the future) telematic city.

The Marchetti constant means that when a city grows beyond its one-hour wide functionality it becomes dysfunctional. That depends on the average speed and density. The lower the density, the closer you will get to that limit, the sooner you will get to that limit. I see around the world that dependent cities are hitting those limits.

Road rage, anti-sprawl movements, market based re-urbanisation, [is the result].

Outside the one-hour city - and certainly Sydney is beyond that - you either say that we must build a new city centre or that growth needs to be redirected. You don't have any other choice. You have got to be serious about a new centre or you say that that growth can go anywhere - Adelaide, Perth, wherever.

Transport planners still seem to think that people will adapt and just increase their travel times. They do not. They will adapt and move, but the city as a whole on average will stick to this one hour per person per day.

This Marchetti constant helps us to understand a lot of things about cities, but it does explain why the inner ring has very high public transport, because within that one hour travel time budget you can use public transport very effectively. It is in fact quicker within that ring than by car for many journeys - but not in the outer suburbs.

So this is a very different city to the outer suburbs.

Automobile dependence can be explained in these terms. It is where a city can only remain functional within that Marchetti constant travel time budget, if it uses automobiles as its major means of transport. If to keep within that one-hour budget the only way you can do it is by car you will do it. You will not somehow switch to using public transport because it is more comfortable or something. It will only compete if it can get you there quicker and as a way of keeping within that budget. So we need alternative options in infrastructure and land use that keep within the one-hour travel budget.

According to Newman, the Marchetti constant leads to two critical policies. The first is to ensure that public transport is faster than cars in all main corridors. Cities that have effectively overcome automobile dependence have faster transit than traffic systems. In Europe, 39 km/h is the average speed of the public transport system, 34 km/h for traffic. In Sydney 37 km/h is the average speed of the traffic and 32 km/h for the transit system.

Buses average around 19 km/h, trains 42 km/h. Newman noted that it is important to have
train systems that can in every corridor enable a faster speed than bus travel.

The second critical policy is to create local centres and town centres that are viable, in an effort to minimise travel and enable priority for walk/bike/bus in those local areas. ‘Viable’ is defined in terms of both residential and jobs / people density. Newman’s work suggests that a density of 35 people per hectare is required to make non-car forms of transport viable. Which means for a centre about one kilometre in diameter, 10,000 people (ie, including both residents and employees) within walking distance of the centre are required to make non-car transport viable.

Larger town centres like Parramatta, which are an alternative to the central business district, require around 100,000 people (residents and jobs) within that catchment area, which Newman defines as approximately a ten kilometre diameter. If these densities are not met, Newman states that the car will remain the dominant form of transport.

TravelSmart household research showed that:
• For 40% of trips people had no option but to use the car as either a driver or passenger;
• For 15% of trips people had no option but to walk, cycle or catch public transport;
• The market share that has a choice of travel mode is therefore 45% of all trips.

Currently people choose the car for 35% and walking, cycling and public transport
for the other 10%.