| A Light Rail Vehicle (LRV) is any form of rolling stock on a Light Rail System. They run on electricity and collect power from overhead catenary wires via a pantograph. LRV's can run as single units or coupled together into trains of four or five cars. They have operator cabs at each end allowing them to be bi-directional.
The first LRVs to be used in North America is the Siemens-Duewag U2. It was placed into service in Edmonton, Alberta, Canada in 1978, closely followed by San Diego and Calgary in 1980, and 1981. The U2 LRV is high-floor meaning that you have to climb stairs or uses raised platforms in order to board the train. North American LRVs manufactured during the `80s and early `90s were of the high-floor variety. Since then, LRV technology has advanced to allow low-floor trains; the benefits being: level loading, easy boarding for strollers, and wheelchair access without the need for special lifts.
Another evolution in LRV technology is the move from DC or direct current motors to AC (alternating current). Advances in microprocessors have allowed for the rapid switching of electrical current required for AC operation. Though AC drives are more complex, their benefits come from reduced maintenance from fewer moving parts. Fittingly, the first North American AC-LRV is the Siemens-Duewag U2-AC, placed in service in Edmonton around 1989. Calgary bought these U2-AC's in 1990 and this is where they now operate daily.
The price of a U2 LRV in 1980 was $1.25 million Canadian ($800,000 American as an estimate). Today's light rail vehicles are priced at about $3 Million American apiece. Current North American LRV's are built to last 30 years, though some sources cite Edmonton's U2s being capable of 50 years with proper maintenance. | 
