What is "hi-v"

The Hedley Hi-V, a New York City Subway car, was built between 1910 and 1911, which were motor cars and then in 1915 an order for trailers that were numbered 4223-4514. These were the first cars built with center doors. They were also the last high voltage cars built for the system as all subway cars delivered afterward had low voltage since high voltage cars were a hazard to both the train operators and track crews, which is probably one of a few reasons why the TA was in a rush to get rid of these cars by the mid 1950s with the R17, R21, and R22 cars. These cars ran on both the West Side and Broadway-7th Ave lines and most likely ran with both the Gibbs and Deckroof Hi-V cars until they retired by 1959 along with what was left of both the Hi-V Gibbs and Hi-V Deckroofs, which were in very small numbers by that point. Some of the cars that were manual door control cars were used in work service until 1960 and possible even as early as 1961 before getting scrapped. The Hedley's standard car body would be incorporated into another fleet of cars known as the Lo-V fleet, which were built from 1915 to 1925. None of the Hedleys were saved, as it was not thought of at the time to preserve for future generations.