The lines were built by the Cathcart District Railway and the Lanarkshire and Ayrshire Railway. The first part opened on 1 March 1886 as a double line from Glasgow Central to then single to Cathcart, doubled on 26 May 1886. The circular route back to Central station via Shawlands and Maxwell Park was completed on 2 April 1894. The Newton and Neilston branches were built to provide a through route from the Lanarkshire coalfields to ports such as Ardrossan on the Ayrshire coast. There is still a junction with other lines at Newton, but the track beyond Neilston has been lifted. The lines originally carried significant amounts of freight, but commuter trains are the only regular users now. Football Specials sometimes run to Mount Florida and for major matches at Hampden Park. When the lines were built much of the land around them was open countryside. The existence of a commuter railway was a major factor in the development of Glasgow's southern suburbs, although until electrification in 1962 there was virtually no passenger service beyond Kirkhill by this route. On weekdays the services have provided a vital transport link for school pupils and college students at nearby schools and higher education establishments, contributing to passenger numbers on top of the commuter traffic. The lines under British Railways were electrified on Monday 28 May 1962 at the standard 25 kV AC, but originally 6.25 kV between and Mount Florida because of limited clearances. The "Blue Trains", units, which had dual voltage capability, replaced steam trains and early diesel units. There was a trial run on the previous day., and over 5,500 passengers were reported as using the new trains in their first morning rush hour.
Built by the Lanarkshire and Ayrshire Railway. Diverges from the Circle via a dive under junction south of and at Cathcart South Junction. The link at Cathcart South junction was put in place during electrification.
Neilston Line
Built by the L&AR. Diverges from the Circle at.
Passenger services
Following electrification in 1962
Round the west side of the Circle onto the L&AR lines eastbound, terminating at. East side services ran to Newton, with many extended to via the Clydesdale Junction Railway. The basic service every 30 minutes was Glasgow Central to Neilston via Mount Florida; Central to Motherwell via Mount Florida; Glasgow Central to Kirkhill via Maxwell Park; and Cathcart Circle.
This included the Hamilton Circle and resulted in east side services terminating at Newton. Peak services from east and west sides operated to Motherwell via Blantyre and Hamilton.
The major change being the extension of west side services from Kirkhill to Newton. Until May 1984 there were four trains an hour on the Newton branch and two trains an hour in each direction around the Circle, in addition to the services on the Neilston branch. From May 1984, both the Newton and Neilston services remained 2 per hour, none turned back at Kirkhill and only one ran the full circle each way.
The basic service is every 30 minutes from Glasgow Central to Neilston via Mount Florida and every hour from Glasgow Central to Newton via Mount Florida, Glasgow Central to Newton via Maxwell Park and the inner and outer Circle service. This frequency gives a 30-minute service on the west side of the Circle, Neilston and Newton branches, three trains per hour at Cathcart and four trains per hour between Glasgow Central and Mount Florida. These service levels are less than those of the 1960s. At peak times the above services combine to have trains running approximately every 5–10 minutes between Glasgow Central and Cathcart, where line capacity permits. Several trains are formed of the maximum six cars at these times. Commuter levels on this line are quite high and therefore a high density service is required at such busy periods.
Rolling stock
Upon electrification in 1962, Class 303s. Following electrification of the Inverclyde Line in 1967, Class 311 units were also used. Following the introduction of the Class 318 in 1986, they made occasional trips onto the Circle. The Class 311 were withdrawn in 1990, and following the introduction of the the Class 303 were withdrawn in 2002 and a major redeployment of the fleet took place, resulting in the Class 314s taking over the line, supplemented occasionally by Classes 318 and 334. In 2014 Class 314s primarily operated the Circle. During peak hours Class 380s are also used on the Circle route only. From December 2016, Class 320s were introduced to the line, working the Circle and Newton via Maxwell Park routes to permit an increase in Class 314 workings on the Inverclyde Line. This was due to a number of Class 380s being reserved for driver training on the newly electrified Glasgow to Edinburgh via Falkirk High route. From the December 2018 timetable change, Class 380s began operating most Neilston services, along with some Circle an Newton services. From February 2019, Class 385s began operating some Circle and Newton services.
Future
Light rail conversion
There have also been proposals to convert the lines to a tram line, but never beyond the initial suggestion stage. Most recently, in December 2008 Transport Scotland's Strategic Transport Projects Review suggested an upgrade of the Circle to light rail as part of a wider light rail network for Glasgow, incorporating both new lines and re-purposed older alignments. If taken forward, this proposal was supposed to have been implemented during the period 2012 - 2022, in line with the scope of the strategic review.
