Average trip duration by mode (top) and purpose (bottom), Melbourne 2012/13 (source data: VISTA)
Average trip duration by mode (top) and purpose (bottom), Melbourne 2012/13 (source data: VISTA)

The average duration of a weekday trip in metropolitan Sydney across all modes and all purposes is 22 minutes and the average distance covered is 8.7 kilometres, according to the NSW Bureau of Transport Statistics. The Victorian Integrated Survey of Travel and Activity (VISTA) reports the corresponding numbers for meltropolitan Melbourne are virtually the same i.e. 23 minutes and 8.9 km respectively.

We know that both duration and distance differ significantly by mode and by purpose. For example, public transport trips in Melbourne take two to three times longer on average than car trips and cover more kilometres. Journeys to work take twice as long – and cover double the distance – as trips to the shops.

Another much cited difference is the “divide” between the inner city and the suburbs. It’s assumed by many that time spent travelling increases significantly with distance from the city centre.

But have a look at the first exhibit which shows trip duration by mode in metropolitan Melbourne. It can be seen the average trip actually takes much the same time in Melbourne’s inner, middle and outer rings i.e. between 22 and 23 minutes (see map of rings here).

This similarity holds for walking, cycling and for private vehicles. The latter is especially important, because private vehicles are the majority mode, accounting for 56% of trips in the inner ring, 73% in the middle ring and 81% in the outer ring.

The only significant difference in trip duration occurs in the case of public transport, where trips originating in the inner ring suburbs average 48 minutes and those in the outer suburbs average 68 minutes. The latter reflects the key use of trains for long trips to work and education destinations in the city centre.

The second exhibit shows average trip duration by purpose in Melbourne. Again, the differences between rings by trip purpose are pretty modest. That should be expected given the dominance of the car in all rings.

The third exhibit (below), however, shows that the difference between rings in terms of average distance travelled per trip (i.e. kilometres) is much larger, increasing with distance from the city centre. This reflects the faster travel speeds available further from the centre.

Thus due largely to express services, public transport users in the outer ring suburbs travel on average for about 40% longer than their counterparts in the inner city but travel 160% further in terms of kilometres. Low congestion means outer ring motorists travel half as far again in the same time as motorists in the inner ring.

Do outer suburban residents travel further because they want to or because they have to? Probably a bit of both, however theory suggests that when travel costs are low, activities tend to concentrate more to capture agglomeration benefits. Both residents and firms get the benefit of economies of scale and scope without spending more time travelling than their counterparts in the inner ring suburbs.

This is a fairly coarse scale. There would be bigger differences in travel time at a smaller scale e.g. if comparing travel by residents of the city centre (say) with the travel behaviour of residents in a particular outer suburb like Werribee.

Average trip distance (kilometres) by mode, Melbourne (source data: VISTA 2012/13)
Average trip distance (kilometres) by mode, Melbourne (source data: VISTA 2012/13)