Service costs and spreading the peak - 2
As well as fares and frequency, another way to spread the peak is to provide express services during shoulder peak. Generally expresses are even more 'peaky' than train frequency. This is good for inner-suburban passengers (as it gives inner suburban stations a broad peak of frequent services) but less favourable for outer suburban commuters who have increased travel times relative to if they travelled during the height of the peak.
The following times indicate the first and last peak direction express trains passing through Caulfield (or Camberwell). 'Express service' is defined as one not stopping at five or more stations*.
Belgrave/Lilydale: 5:46am - 10:20am
Cranbourne/Pakenham: 6:12am - 8:36am
Frankston: 7:43am - 8:47am
Belgrave/Lilydale: 3:40pm - 7:37pm
Cranbourne/Pakenham: 4:41pm - 6:06pm
Frankston: 5:16pm - 6:21pm
(*) Based on 30/9/07 timetables, which are out of date. Will be updated with new data.
The main limitation of the above spans is that they change according to where you draw the line on the number of stations the expresses miss. For example, there are many trains that express through three stations. This will broaden the span - to most of the day in the extreme case of the Frankston line where it becomes meaningless.
Because it's better to spread the peak and this requires both service and behavioural changes, I opted only to include the faster express trains. This is in line with passenger behaviour - passengers able to will prefer the faster expresses, even if the travel time saving is small. Shoulder travellers on some lines pay a penalty in reduced service frequencies and/or fewer expresses, and tackling this is helping to spread the peak and increase efficiency.
What do the above lists show? The Belgrave/Lilydale lines have wide peak express spans, with express services running well into the shoulders. The Frankston line has very narrow peak express windows (literally 'peak hour'), although it has many lesser expresses outside those times and during the day. Cranbourne/Pakenham has expresses opearating during most peak times. The most conspicuous gaps where there are no or slow expresses are on the Frankston line before 5pm and on both the Cranbourne/Pakenham and Frankston lines from about 8:30am. These early finishes do not encourage 9:30am starting, though if this was encouraged the after 6pm services also need attention.
The narrow express peaks on the Frankston line warrant further attention. Planning for it is complicated by the interplay with the other Caulfield group lines. Service priorities are elsewhere and nowhere is the competition fiercer but on the Caulfield group. The number of Frankston expresses appear to be held back by a need to provide a service to inner suburban stations (Malvern - Hawksburn) that cannot be satisfied by existing Carrum, Mordialloc, Cheltenham, Westall and Oakleigh local trains alone.
Current arrangements have the advantage of relieving the burden on the Cranbourne/Pakenham line (which has heavier patronage but less infrastructure). However Frankston is also a long line with its own distinct needs. These are a wider selection of expresses to serve areas beyond about Moorabbin and more frequent service closer in.
This makes the concept of a two-tiered service based on frequent local and express trains running over a longer span attractive with better use of the existing third track to Moorabbin. However it could also mean that some zone 1 stations (eg Glenhuntly or Carnegie) may lose express trains, and more services would miss the loop, running direct to Flinders Street.
To summarise, spreading the peak by making shoulder peak service more attractive is a viable way to improve capacity and network efficiency. While it can't cope with meeting long-term requirements, it's a worthwhile short and medium term strategy to relieve pressure on the network and has an exceptional return per dollar spent.