UIC and ОСЖД (OSZhD) are two international organizations caring about everything concerning international railroad traffic. UIC is West European; ОСЖД (OSZhD) is East European and Asian.
After World War II the growing international railroad traffic in Europe caused more and more problems related to the compatibility of various countries' infrastructure and equipment. So both organizations defined various standards. Their standards were largely similar but not identical. Both organizations' standards for passenger cars became effective in the early 1960's—ОСЖД (OSZhD) in 1962, UIC in 1963.
These standards included both technical (dimensions, crash worthiness etc.) and comfort (space in both classes, size of windows etc.) norms.
ОСЖД (OSZhD) types:
- A type—body length 26.1 meters (85' 7 1/2''); length over buffers / coupled length 26.4 meters (86' 7 1/3'') (never built, as far as I know)
- B type—body length 24.2 meters(79' 4 3/4''); length over buffers / coupled length 24.5 meters (80' 4 1/2'')
- X type—body length 26.1 meters (85' 7 1/2''); length over buffers / coupled length 26.4 meters (86' 7 1/3'')
- Y type—body length 24.2 meters(79' 4 3/4''); length over buffers / coupled length 24.5 meters (80' 4 1/2'')
- Z type—body length 26.1 meters (85' 7 1/2''); length over buffers / coupled length 26.4 meters (86' 7 1/3'') (intruduced only in the 1970's)
Different sources call different terms to be deciding about the subtypes. I don't know which one is true. One version is following.
- Z1 type—top speed of at least 200 km/h (124 mph)
- Z2 type—top speed of at least 160 km/h (99 mph)
- Z type—others
- Z1 type—air-conditioned
- Z2 type—not air-conditioned
When the ОСЖД (OSZhD) standards were finished in 1962, GDR and Bulgaria immediately started their productions of B-type cars. But there was a problem. West European countries didn't like them at all. I'm not sure but I think, I have read somewhere that some countries even barred them from their rails.
The solution was simple. There were eight ОСЖД (OSZhD) members in Europe. Soviet Union didn't care about international standards at all. Albania was kind of less developed country related to railroads without any rail connection to other nations. The other six nations were also UIC members. And UIC standards became effective only one year later and UIC type Y was very similar to ОСЖД (OSZhD) type B. So they switched over to and started with UIC's Y type, respectively.
GDR tried to make it even better. They constructed a type of cars which kept to both ОСЖД-(OSZhD)-type-B and UIC-type-Y standards. Because of the circumstances mentioned before, it was actually not neccessary. But it almost "fell into place" while using their experiences gathered with B and Y types to improve the cars they made. And because not only both Y and B standards were kept to but mass production started in 1970, they called their new type Y/B70. But as far as I know this designation is hardly used outside Germany.
In West Europe some nations started with Y- and some with X-type cars. Some nations kept to their own standards. Some nations relatively soon changed from Y- to X-type cars (e. g. Italy).
In the 1960's and 1970's the West European TEE (TransEuropExpress) network raised the bar for international high-quality trains. So UIC added another type in the 1970's—Z type. Z type based largely on the EUROFIMA cars which were under construction that time. The length was taken over from X type. But they changed other details—like the minimum length of compartments, for instance. I'm not sure if it was intended, but X type became obsolete this way.
East European railroads changed to longer cars only after UIC's Z type was introduced. So X-type cars have never been made there. They only used B-, Y- and Z-type standards.
EUROFIMA is a cooperation of six West European national railroads which constructed, purchased and financed high-quality passenger cars for their members' international trains.
There are five versions of cars constructed by EUROFIMA—1st, 2nd and mixed 1st and 2nd class coaches, 2nd class couchette coaches and sleepers. They all were air-conditioned compartment cars with sliding doors. But there was no nation purchasing all versions. Germany for instance bought only 1st class coaches and sleepers. Most nations bought 1st and 2nd class coaches. EUROFIMA-type sleepers are also relatively common. Couchette coaches were but rare and mixed 1st and 2nd class coaches have never been ordered, as far as I know.
But the EUROFIMA construction was relatively short-lived. Already after a short time most railroads purchased other types of cars for the same purpose. Most of them ordered open-seating cars and diners matching the EUROFIMA-cars' appearance. Some also bought combines or baggage cars looking like EUROFIMAs or even cars with both compartment and open-seating areas.
The construction of those cars bases on EUROFIMA cars but EUROFIMA cars themselves are not very common.
Those standardized cars were intended for international traffic mainly. Of course, (almost) all nations continued purchasing other types of cars (double-decker cars, for instance) mainly for their inland traffic. And older cars have also continued to be used for some decades; some even got new car bodies. So not every passenger car in Europe belongs to one of those types.