This diesel locomotive is of Chinese origin. It is in North Korea known as the class BJ where BJ stands for Beijing. They were bought second hand from China since 2002. It has a top speed of 120 km/h and a power rating of 1990 kW. They were built in China 1970-1991.
Picture from the Pyongyang station 1.6.2018 by Markku Salo.

An express train is stopping at the station of Yeomju, fairly close to the Chinese border. Apparently the train is serving in the North Korea to China transit traffic. The locomotive is a six axle machine of the Chinese type DF4B. North Korea bought at least 36 of these machines from China second hand 2006-2008. These machines were built in China since 1984 by at least four different factories. Its top speed is 100 km/h and it has a power rating of 2650 kW.
Picture from Yeomju station 29.5.2018 by Markku Salo.

Another view of the same class DF4B locomotive.
Picture from Yeomju station 29.5.2018 by Markku Salo.

Another class DF4B locomotive bought second hand from China, but this one is in the standard North Korean painting instead of the Chinese original blue colours.
Picture from Jeongjucheongnyeon station 29.5.2018 by Markku Salo.

A former East German V200 locomotive, built as the type M62 in former Soviet Union (now Luhansk, Ukraine), delivered to East Germany and later sold to North Korea. Here seen at Yokjon Dong in Pyongyang, North Korea. In North Korea the locomotive is called Naeyeon 706. North Korea bought these locomotives in several batches, some directly from the factory in Ukraine, some used from the DDR and Czechoslovakia.
Picture 5.10.2013 by Clay Gilliland. This file is licensed under the Creative Commons Attribution-Share Alike 2.0 Generic license.

A Kŭmsŏng class locomotive. This is a North Korean copy of the Soviet built M62 machines. When the Koreans got some of the M62 machines, they reverse engineered the locomotive and also its engine and began building their own copies. But probably only two copy machines were ever made. This locomotive was put on display in Pyongyang in the Museum of the Three Revolutions.
Picture by Wikimedia Commons user calflier001 23.10.2012 in Pyongyang, North Korea. This file is licensed under the Creative Commons Attribution-Share Alike 2.0 Generic license.

Also this locomotive no. 4054 is displayed at the Museum of the Three Revolutions in Pyongyang. It is of the Ch'ŏngnyŏnjŏl Kinyŏm ("Youth Day Memorial") class. It is a four axle electric locomotive for 3000 V DC. At least 56 of these machines were built by the Kim Chong-t'ae Electric Locomotive Works in Pyŏngyang. This model is designed and built in North Korea, but it is based on the French Francorail MTU CSE26-21 dieselelectric locomotive design, eight of which were sold to North Korea in 1981. These electric copy machines were built in the 1990s.
Picture by Wikimedia Commons user calflier001 23.10.2012 in Pyongyang, North Korea. This file is licensed under the Creative Commons Attribution-Share Alike 2.0 Generic license.

This six axle locomotive is of the class Red Flag 1. It is seen here in the standard North Korean locomotive paintings. These machines were built since 1961. It has a top speed of 120 km/h and a power rating of (only) 2250 kW. The producer was Kim Chong-t'ae Electric Locomotive Works in North Korea. Over 150 locomotives of this type were produced. This type was the very first totally in North Korea designed and built electric locomotive.
Picture by Markku Salo from the Pyongyang station 1.6.2018.

This six axle locomotive is of the class Red Flag 2. It is a derivative of the earlier Red Flag 1, built in the 1980s by the Kim Chong-t'ae Electric Locomotive Works. Over 150 locomotives of this type were built. It has a top speed of 120 km/h and a power rating of 3180 kW. The type was especially intended for fast passenger express trains, but is used also in cargo traffic.
Picture from the Jeongjucheongnyeon station 29.5.2018 by Markku Salo.

This diesel shunter locomotive type is also called the Red Flag. Also these were built by the Kim Chong-t'ae Electric Locomotive Works in 1965. The type is an approximate copy of the Japanese national railways type DD13. Possibly it is the result of Koreans reverse engineering the Japanese model.
Picture by Markku Salo from the Pyongyang station 1.6.2018.

Another picture of the same Red Flag shunter.
Picture by Markku Salo from the Pyongyang station 1.6.2018.

Earlier tourists were only allowed to use the Pyongyang metro between the two stations of Puhŭng and Yŏnggwang. This led to a conspiracy theory that there was nothing else in addition to these two stations. But after 2010 tourists have been admitted in groups to other stations too. However, rumours still say that there would exist secret metro lines only for politically important people and the military in addition to the lines open to the public. We still don't know. There are now 16 public stations. This is the Puhŭng station, one of the really fine ones that were already early on shown to tourists.
Picture from the Puhŭng metro station in Pyongyang 6.8.2012 by Roman Bansen. This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Puhŭng station still looks very much the same in 2018.
Picture 30.5.2018 by Markku Salo.

Another view of the metro train at Puhŭng metro station in Pyongyang.
Picture from the Puhŭng metro station in Pyongyang 6.8.2012 by Roman Bansen. This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Metro train at the Puhŭng station. There are a lot of guards in the Pyongyang metro. For example in the cab there is a guard in addition to the driver.
Picture 30.5.2018 by Markku Salo.

Metro train arriving at the Puhŭng station.
Picture 30.5.2018 by Markku Salo.