I found this interesting thread and thought that i would make a comment as i am a railway enthusiast who has travelled extensively across the Turkmen and Iranian rail networks as well as other countries in the region.
This website is pretty useless and is missing a massive amount of trains and routes and stations. It only seems to show the major fast intercity trains only. There are a huge amount of slower trains and regional trains that are completely missing. I have the big official timetable book which i picked up when i was there late last year (it was extremely hard to get hold of but luckily with the help of a Turkmen friend and speaking to the Station Master in Ashgabat i managed to get one) and there are so many more trains than what are shown.
There is still a weekly train between Mary and Serakhs and backs again. It runs once a week in both directions and has done for years. Although note that it terminates on the Turkmenistan side of Serakhs and then you have to make your own way across the border to or from Iran to connect with the trains on the Iran side of Serakhs to continue your journey.
So the Serakhs to Mary train is still running. Also note at Mary there is frequent trains to and from Ashgabat and most other major cities. I think the website only shows the major trains that can be pre booked. This service between Serakhs and Mary is a very basic train and you buy your tickets onboard from the Guard as even ticket offices don't sell tickets for these basic slow regional services. It is extremely cheap though (less than £1.00 for a ticket) like most things in this region.
The train numbers are 6423 for the Northbound one and 6424 for the Southbound one. It leaves Mary at 07:10 and arrives Serakhs at 11:40 and in the other direction it leaves Serakhs at 19:10 and arrives Mary at 23:40 so it is about four hours and thirty minutes journey. Both of these journeys are on Monday only. The train sits around in Serakhs on Monday all day.
During my last visit to Turkmenistan late last year i took the Serakhs to Mary train in both directions as i was trying to do Tehran to Ashgabat entirely by train (which i did other than the small gap across the border between the two Serakhs in each country) which is possible with careful planning.
There are plenty of other services missing as well so it is a shame that the website doesn't show these.
Turkmenistan is well worth visiting. It is a strange place though. You can easily spend the whole day walking around Ashgabat and barely see a single other person other than some people sweeping the streets. It is like North Korea but a bit more freedom (especially as i have always travelled independently on a Transit Visa with no guide) so it is worth a visit. Iran is most certainly worth a visit as well. It is by far my favourite country and i keep going back. You won't find a friendlier country anywhere.
Thanks for so much local info about travelling in Turkmenistan - fascinating.
As to the friendliness towards visitors in Iran, others have told me of the great hospitality of ordinary people there (though the experience for women is a bit different in some situations). However, they - and my Iranian friends over here (some of them effectively in exile here) - point out that though this
is true with regard to many "ordinary" people, it's certainly
not true as far as much of Iranian officialdom is concerned ... unless you keep your mouth shut about anything controversial (ie what those in power in Iran deem controversial!). If you're someone who thinks it normal to refer openly to the worldview you have, and the principles you live by - or (depending on which it is) which sex you are attracted to - then in many cases you might find Iran threatening rather than welcoming.