Archive for December, 2018

The 2017 timetable changes to Sydney Trains saw a massive expansion of the all-day 15-minute frequency network, from 88 stations (49% of stations) to 126 stations (71% of stations). This level of service requires a minimum of 4 trains per hour in each direction, spaced evenly throughout that hour. This level of service has been deemed “tun-up-and-go”, where passengers need not worry about a timetable.

Stations with a train every 15 minutes or less all day. (Source: Adapted by author from Sydney Trains.)

However, there are several sections of the network with more than 4 trains per hour all-day: 14 trains per hour in the city and even 10 trains per hour outside of the city on some lines, in many cases with wait times of less than 10 minutes. This post will investigate which portions of these lines enjoy these higher frequencies and identify which lines are approaching an improved turn-up-and-go service. The weekday timetables from roughly midday are used for this, which are slightly different to the weekend timetables.

There are 3 lines whose inner-city sections contain high frequency services, with maximum wait times of 10 minutes between trains: the T4 Line between Bondi Junction and Sydenham, most of the T1 Line between Chatswood and Redfern (excluding Waverton/Wollstonecraft/Artarmon as not all trains stop at these stations), and the T8 Line between Wolli Creek and the City Circle.

EDIT: It has been pointed out that since the closure of the Epping to Chatswood Line for metro conversion, North Shore trains now use Linfield as the turn-back station, rather than Chatswood. Therefore, these higher frequencies extend past Chatswood and up to Roseville/Linfield.

Lines with a train every 10 minutes or less all day. (Source: Adapted by author from Sydney Trains.)

But looking at the maximum wait times can be misleading. As an extreme example, imagine a line with trains every 6 minutes during the first half of each hour, then no trains during the second half of each hour. Even though the maximum wait time in this situation is 30 minutes, a passenger arriving at a random moment during the hour is just as likely to wait a maximum of 6 minutes as they would 30 minutes. By taking the (weighted) average of these two times, that being 18 minutes, we get a more accurate idea of what is known as the expected maximum wait times.

Maximum wait times assume a passenger always arrives just as a train is departing, which is rarely the case. So, dividing the expected maximum wait time in half gives the average wait time, in other words, a passenger arriving at a random moment in a given hour would be just as likely to have a longer wait time as they are to have a shorter wait time.

Based on this calculation, T1 has the shortest average wait time. T1 has an average wait time, depending on the direction of travel, of 3:22 or 3:28 (wait times measured in minutes:seconds). This means that a passenger’s next train is more likely than not to arrive within 3 ½ minutes. Next shortest is T8 with, again depending on direction of travel, of either 3:46 or 3:54. The longest average wait of the 3 lines is T4 at 5:00, regardless of direction of travel.

Lines and stations with a train every 10 minutes or less all day. (Source: Adapted by author from Sydney Trains.)

Many lines maintain high frequencies beyond the 4 per hour required for maximum 15-minute wait times but a mix of express and all stations stopping patterns mean that only a few individual stations have average wait times at or below 5 minutes. Two stations that do this are Strathfield and Newtown, although both do sometimes have a maximum wait time of 11 minutes, which is above the 10 minute cut-off mentioned above. The shortest average wait time of these two is on T1 from Strathfield to Central of 2:58. Next shortest is T2 from Newtown to the City Circle with an average wait time, depending on the direction of travel, of 3:54 or 4:34.

Expanding the turn-up-and-go network

There are several ways to improve services to achieve turn-up-and-go status: even out spacing between services to reduce bunching, increase train frequencies, and extend existing services beyond their terminating station.

The first, even out spacing, should be a low hanging fruit for Sydney Trains as it does not require any additional services being run, only an adjusting of existing services. However, this is not always possible due to conflicts with other trains as several branches join up in the central core of the network.

The second, increase train frequencies, works best when a marginal addition leads to a large reduction in maximum wait times. For example, going from 6 or 7 trains per hour to 8 can reduce gaps in service from 15 minutes down to 8 or 9 minutes.

The third, extend existing services requires sufficient turn-back capacity at stations further down the line. A lack of such facilities can hold up trains, resulting in delays. However, if possible, this is often a cheaper way of increasing frequencies than adding a whole new train service.

Potential lines and stations with a train every 10 minutes or less all day. (Source: Adapted by author from Sydney Trains.)

On example of where this could be achieved is the T2 Southwest and T5 Cumberland Lines, between Leppington and Merrylands, which currently see 6 trains per hour. Adding an additional 2 trains per hour on T5 and adjusting its Leppington bound trains to depart 2 minute earlier would see the maximum wait time drop from 15 minutes to 9 and the average wait time drop from approximately 6 minutes to under 4 minutes. This would be the first high frequency line on the Sydney Trains network not centred around the Sydney CBD; instead this would be centred around the Liverpool CBD.

Another area for investigation could be to extend intercity services from the Central Coast and Blue Mountains out to North Sydney, rather than terminating at Central Station’s Sydney Terminal. This is complicated by the availability of paths due to converging branches of different lines and the 190m long V-Sets that operate on many intercity routes. If these are replaced by OSCARS or the new intercity trains that are set to enter service next year, both 160m long and able to operate in the shorter underground stations of the Sydney CBD, then this may be possible. Doing so could reduce average wait times on T1 stations between Central and North Sydney from the current 3 ½ minutes down to 2 ½ minutes.

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