The Cowan Bank is an 8.6 km double-track section of the standard gauge main north railway line running between Sydney, New South Wales, Australia and Newcastle (168.1 km north of Sydney), one of the busiest rail corridors in Australia. The Cowan Bank is situated between Cowan railway station 48.8 km north of Sydney, and Hawkesbury River railway station 57.4 km north of Sydney. It has an average grade of 2.5% (1 in 40) rising from close to sea level at Hawkesbury River railway station to a height of 200m on the ridge top at Cowan railway station.
The Cowan Bank has 5 tunnels (of which 4 are still in use), no level or grade crossings and two road bridges. The line crosses under the Pacific Highway twice, once using a road bridge near Cowan station and again while passing through Boronia #1 tunnel. It crosses under the Sydney-Newcastle Freeway while passing through Boronia #2 tunnel. The line was built through very rugged and heavily forested terrain on the western edge of the Kuring-gai Chase National Park. Because of its isolated location there are very few places from where the track can be observed - sections of the Pacific Highway on the ridge between Cowan and the Hawkesbury River provide a few vantage points.
Bank engines were attached to the rear of trains at Hawkesbury River station to assist them in the climb and were detached at Cowan station. After assisting a train up the bank, the bank engine would usually return to Hawkesbury River station to await the next train. Bank engines are no longer used on the line.
Because of its long grade and proximity to locomotive manufacturing and maintenance facilities in both Sydney and Newcastle, the Cowan Bank is often used to test locomotives and power cars.
The single track line between Cowan and Hawkesbury River stations was completed in 1887. Five tunnels (Boronia #1 to Boronia #5) were built as double track tunnels but initially only a single track was laid through them. The line was duplicated in stages between 1907 and 1909. Boronia #5 tunnel was abandoned when the tracks were realigned during the duplication.
Bi-directional running was introduced in 1996 to allow faster up trains to use the adjacent down track to overtake slower freight trains climbing the bank. Track cross-overs were installed at Cowan railway station, between Boronia #1 and #2 tunnels, and just south of Hawkesbury River railway station.
Five serious incidents have occurred to date on the Cowan bank.
- 21 June 1887 - an excursion train from Sydney ran out of control down the Bank and collided with freight wagons stored on a siding at Hawkesbury River railway station. 6 fatalities and 70 injured.
- 20 January 1944 - a local road bus stalled on the level crossing at Brooklyn Road and was hit by the north bound Kempsey mail train. 17 fatalities.
- 9 June 1948 - a rear end collision between the stationary Newcastle Flyer bound for Sydney, which had stalled on the bank, and the following Cessnock Express. 43 passengers were injured.
- 6 November 1974 - a side collision between a CityRail Intercity electric train and a passing a freight train. No injuries.
- 6 May 1990 - a rear end collision between a stationary passenger excursion train bound for Sydney hauled by historic steam locomotive 3801, which had stalled between Boronia #2 and #3 tunnels, and a following Sydney bound CityRail Intercity electric train. There were 6 fatalities, including the driver of the Intercity electric train, and 99 injured.