Question:

I am planning to visit Iran for short trip, 10~14 days. I would like to spend couple of days in Tehran and also I would like to visit Yazd. I found that train service is operated only during nigh time. Can you confirm or deny this? If it is true, there are two options for us, rent a car or flight. Is it worth to rent a car for tehran-yazd transport or not? If it is just "8hours highway trip" it is not worth for us, if there is some point of interest, then probably yes.

Answer:

There are both night and day trains. But you can fly to Yazd and do the return by train. Check this page for more information:Iran transport services.
It is also another option to hire a car to start from Tehran early in the morning, visit Abyaneh and Kashan along the way. Have Iranian lunch in the restaurant in Abyaneh. Finally, arrive to Yazd early evening. But you should consider that in summer this route is hot and intolerable.

Check the cheapest Iran tours.