T4 Eastern Suburbs and Illawarra line

The T4 Eastern Suburbs and Illawarra Line is a suburban train service operated by Sydney Trains between Bondi Junction, Waterfall and Cronulla. The line is coded with the sign on maps and at stations. The Illawarra Line is known for being the first railway line in Sydney to operate electric train services, which first commenced in March 1926.

Route
The Eastern Suburbs Line runs between Bondi Junction in Sydney's east and Redfern, just south of the Sydney central business district. It is mostly underground, and consists of 7 kilometres of bored tunnels and 1.5 kilometres of cut and cover tunnels, with only 2 kilometres above ground. In the Eastern Suburbs, three tunnels proceed in a westerly direction from Bondi Junction via Edgecliff and Kings Cross; in each of these tunnels there are stations. Between Bondi Junction and Edgecliff there is a short open-air cutting in Woollahra, and between Edgecliff and Kings Cross there is a short viaduct over Rushcutters Bay.

From Kings Cross, the line proceeds west towards the Sydney Central Business District on a viaduct that passes over the suburb of Woolloomooloo and the Eastern Distributor. The line then passes into a tunnel underneath the Art Gallery of New South Wales to a station underneath Martin Place. Turning south, the line proceeds through Town Hall, Central and Redfern stations, before emerging behind the Eveleigh Railway Workshops. The line is double track throughout, with turnback sidings at Martin Place and Bondi Junction for citybound trains, and at Central for trains from Bondi Junction.

The Illawarra Line commences at Illawarra Junction at Redfern and travel on the 'Illawarra' (eastern pair) tracks. A dive tunnel allows Intercity services from the South Coast Line to cross underneath the main suburban lines to access Central station. The Illawarra lines are also connected at this point to the Illawarra Relief Lines which emerge from underground and lead to the Eastern Suburbs Line.

From Illawarra Junction, four tracks head south through Erskineville and St Peters to Sydenham station. The 'main' pair of tracks are used by T4 and South Coast Line trains and the 'local' pair by T3 and peak T8 trains. At Sydenham, the Bankstown railway line branches off, but T8 trains continue along the Illawarra line until Wolli Creek, where a junction to the East Hills line branches off.

South of Wolli Creek station, a crossover allows trains from the 'main' pair of tracks to switch to the 'local' pair. This is used by peak hour all-stations T4 trains. The four track section ends at Hurstville. The line then continues as two tracks south towards Sutherland, crossing the Georges River via the Como railway bridge between Oatley and Como. Both tracks are bi-directionally signalled between Hurstville and Sutherland.

At Sutherland, the Cronulla line branches in an easterly direction through Kirrawee, Gymea, Miranda, Caringbah, Woolooware and Cronulla. The Cronulla branch opened in 1939 as the replacement for a former tram line.

The main line then heads in a southerly direction, through Loftus, Engadine and Heathcote, parallel to the Princes Highway to the west and bordering the Royal National Park on its eastern side until Waterfall, the last suburb on the T4 line in the Sydney metropolitan area. The track continues south from here as the South Coast Line through the Royal National Park towards the Illawarra region.

Services
The current running operations for passenger services have remained generally unchanged since 1981 with the integration of the Illawarra line and the Eastern Suburbs Railway. Suburban services utilise Erskineville Junction and proceed to Central and Bondi Junction.

Trains on the Eastern Suburbs and Illawarra typically operate with 16 trains per hour (tph) during the peak, 6tph off-peak, and 4tph on late nights. The line has many possible termini, as seen in the table below, however only a small subset are used regularly. Bondi Junction is the only regularly used northern terminus. Waterfall and Cronulla are the regular southern termini, with Hurstville added during the peak.

The line also has a wide variety of stopping patterns. In general, Hurstville (peak only) and Waterfall (weekends and off-peak) trains stop at the smaller stations (e.g. Sydenham, Tempe, Arncliffe, Banksia, Como), while Cronulla trains skip most smaller stations. One afternoon train on weekdays also extends to Helensburgh (one station south of Waterfall).

On weekends, Waterfall services stop all stations between Sydenham and Mortdale, skipping Oatley and Como, and then going all-stations from Jannali to Waterfall. Cronulla services run to two stopping patterns - all-stations from Hurstville to Sutherland, and express services from Hurstville to Sutherland with a stop at Mortdale in-between.

Fleet
The last S sets were withdrawn from Mortdale Maintenance Depot in March 2013 (after the last S set ran T4 line services on 8th March 2013). This line is now operated by Tangara T sets for all services, except a few Hurstville services in the morning peak, which are operated by OSCAR H sets.

The T4 Eastern Suburbs and Illawarra Line is the only major suburban line on the Sydney Trains network to not operate Waratah A sets. This is because the substations on the line cannot handle the high current draw of having many 4th generation trains on the line at once. Another strong reason is that this makes the line to be more self-contained, having its dedicated fleet of trains.

The T4 line is one of the most self-contained lines on the network, making it one of the lines with the highest train punctuality. All trains for the line are stabled at Bondi Junction, Mortdale or Cronulla, both of which are on the line. It almost has a dedicated fleet, with the only exceptions being H sets from the South Coast and some T sets being swapped to/from Hornsby overnight. It also doesn't share any track with other lines (except for the South Coast line) and is mostly controlled from Sydenham Control Centre (which only controls T3/4 lines).

Trackwork services
Some services on the T4 line occasionally make additional stops at Erskineville and St Peters stations if the T3 Bankstown Line is affected by trackwork, or during major service disruptions. Due to the Bankstown Line from Sydenham to Bankstown being converted to rapid-transit for the Sydney Metro City & Southwest network starting in 2024, Erskineville and St Peters are expected to be permanently serviced by the T4 line.

In instances where the Eastern Suburbs Line is closed for trackwork, T4 Illawarra Line trains from both Waterfall and Cronulla divert to North Sydney to terminate.

In instances where the entire Illawarra Line (Central ↔ Waterfall/Cronulla) is closed, trains run on the Eastern Suburbs Line from Bondi Junction to Central only, with a turnback provided south of platforms 24/25 at Central to allow trains to terminate.

If the line between Sydenham and Central is closed, trains are split into three sections, with an interchange required at Wolli Creek (if travelling from the Illawarra Line to the City) or Central (when travelling from the Eastern Suburbs to access Wolli Creek for Illawarra Line interchange). The sections are as follows:


 * Bondi Junction ↔ Central
 * Sydenham ↔ Cronulla
 * Hurstville ↔ Waterfall (as there is only 4tph terminating capacity at Sydenham)

Some late night trackwork periods close the main lines, forcing trains to use the local lines. Trains bypass Wolli Creek in these circumstances, with a trackwork bus service to operate between Sydenham, Wolli Creek and Arncliffe. All T4 trains make an additional stop at Arncliffe during these periods to allow for interchange with the bus service.