Stockholm commuter trains ("pendeltågen")

Stockholm has had regional train service since the late 1800s. However, in the early 1960s, the services' difficult financial situation made it clear that a public takeover was necessary. The public transport company SL (Storstockholms Lokaltrafik -- Greater Stockholm Transport), which took over the former SS (Stockholms Spårvägar -- Stockholm Tramways, owned by the city of Stockholm) on 1 January 1967 and was (and is still) owned by the Stockholm County Council, initiated a completely different kind of regional rail service in May of 1968, using newly purchased EMU trainsets. These cars of type X1, and the similar type X10 cars purchased in the early 1980s, are still providing the regional rail service in Stockholm County. Until 6 January 2000, the service was contracted out to SJ (Statens Järnvägar -- the Swedish State Railways) for operation of trains and stations. More on this below.

The pendeltåg have suffered a couple of debacles during their rather short history. From the late 1960s until the late 1970s, the winters in the Stockholm region were relatively mild, but beginning in the late 1970s a series of severe winters exposed the X1 cars' vulnerability to snow and cold weather. The principal problem was that the cars' air intakes sucked snow into the motors, where at the very low temperatures being experienced it froze to ice, putting the motors out of commission. Breakdowns were an almost hourly occurrence, locomotive-hauled consists had to be pressed into service to provide a semblance of normal operation, and the term "pendeltågselände" ("commuter train misery") was coined. These problems were partially solved by the building of a de-icing facility at the main shops in Älvsjö and some minor modifications to the cars themselves, but they can still crop up.
On 6 January 2000, a consortium called Citypendeln took over operation of the pendeltåg from SJ, having won the contract in a competitive tender. Unfortunately, Citypendeln had handled the takeover of staff rather badly, creating considerable badwill with the unions, and (for example) not notifying staff until the last minute of how their schedules would look. But the staff had until the last minute to decide whether to switch over to Citypendeln, and at the last minute large numbers of them decided not to, so there was Citypendeln, all dressed up and no engineers to run its trains.
The first couple of months after the takeover were unmitigated chaos, with only a fraction of timetabled trains being run. But fairly soon, Citypendeln started improving working conditions for its engineers and raising their salaries to attract more candidates, and by the end of the year, service was fairly close to normal.
I personally pretty much abandoned the pendeltåg after the Citypendeln takeover, because the schedules were very difficult to keep up with (they tended to change as the staff situation changed) and, of course, because the service was so unreliable. Now, my travel patterns have pretty much established themselves, and they rarely include the pendeltåg. That's unfortunate in a way; one of the reasons I moved to Sundbyberg was that it has both subway and commuter rail service. But particularly now that I work on the subway, I just generally find it easier to use the subway.

The pendeltåg consists of two base lines, one running from Bålsta in the northwest to Nynäshamn in the south, the other from Märsta in the north to Södertälje in the southwest. The table below shows the lines, with links for the stations I have pictures from. The only real variations in the system are short turns; e.g., most southbound trains on the line to Nynäshamn turn back at Västerhaninge (when there are four trains per hour, as there usually are off-peak, only one of the four trains goes to Nynäshamn), and many rush-hour trains northbound, toward Märsta, turn back at Upplands Väsby.
There is also a small line running from Södertälje centrum to Gnesta, which I've indicated below as well. The transfer between the "main" line that comes from Stockholm and the small line to Gnesta occurs at Södertälje hamn.