Network size versus service intensity

Is it better for a city's rail network to have 300km of track and services every 30 minutes, or only 100km of track but trains every few minutes?

Adelaide and Brisbane are examples of the former, whereas Toronto exemplifies the latter. It is desirable to have an extensive rail network. However it is also helpful to have an intensive service so that people can turn up and know that there'll be a train in a few minutes. The latter often gets lost, since timetables and service planning are seen to be less exciting than hardware such as new stations, new trains and new lines.

An interesting discussion that touches on these matters as they relate to Melbourne recently appeared on the Railpage. Particularly relevant are the posts from 'penov' (on the suburban network) and 'DMU Dave' who cites a 'Railway Digest' article by Albert Isaacs on the country network.

Melbourne's population has grown and spread over time but there has been relatively little change to the extent of the suburban rail network since the 1930s, something that was pointed out in a recent 'Age' opinion piece.

As the article states, some lines have closed, eg Healesville, Mornington, East Kew, etc. However while it covers network extent, it neglects mention of service intensity across the network. It is this service level that is the main determinant of whether a rail service should be regarded as rural or urban in character.

Hence it would be interesting to repeat the exercise, but this time defining the urban rail network as the area having an off-peak service headway of 20 minutes or better. If this is followed, it turns out that Mornington and Healesville never had a suburban level service, so should not be included, even when they ran. Ditto for Dandenong, which according to penov's post, only ran every hour. In contrast established inner areas such as Williamstown, Brighton and Essendon had a more intensive service in the 1930s than they do now. The only reason why this wasn't also true for Glenhuntly also was the off-peak service increase on the Caulfield group in the 1990s.

Though I haven't done the calculations, I suspect that if you looked at the track kilometres of line that enjoyed a 20 minute or better service in the 1930s, compared to now, you will find a more extensive network today. Inner areas lost service, while suburbanising outer areas like Dandenong gained service.

What about country lines? The 'Railway Digest' article says that there are more trains now than in the 1930s. However the difference is that many smaller lines that only saw one train a day have closed. But on the major lines services have increased. In other words, a more intensive service over a smaller network is offered. This is comparable to the situation for outer suburbs but opposite to the case for the inner suburbs, whose service intensity decreased.

So in summary:

- Service intensity over the inner parts of the suburban network has declined (now there are less frequent trains on the same tracks)
- Service intensity over the outer parts of the outer part of the suburban network has increased (more trains on fewer lines)
- Service intensity over the rural network has increased (more trains on fewer lines)