Background

With the opening of the Meishin Expressway between Nagoya and Kobe in 1965 and the Tomei Expressway between Tokyo and Nagoya in 1968, JNR faced increasing competition for freight transport from road hauliers. JNR therefore developed the "10000 series" freight wagons (KoKi 10000 and KoKiFu 10000 container flat wagons, ReSa 10000 and ReMuFu 10000 refrigerated wagons, and WaKi 10000 bogie vans) capable of operating at 100 km/h (60 mph). Express freight services formed of these wagons were introduced on the Tokaido Main Line and Sanyo Main Line from October 1966 using Class EF65-500 electric locomotives built in 1965. These locomotives were designed to be used in pairs hauling 1,000-tonne freight trains, but as pairs of locomotives drew excessive current from the overhead wires, 1,000-tonne freight trains had to be split into 600-tonne and 400-tonne sections when operating on the Sanyo Main Line. This led to the need for a new locomotive design that would be capable of hauling 1,000-tonne trains singly.^[5]

Prototype

A prototype locomotive, initially classified EF90 and numbered EF90 1, was built by Kawasaki Sharyo in 1966. It had a total power output of 3.9 MW (5,230 hp), making it the world's most powerful narrow-gauge locomotive at the time.^[5]

EF66 901 was retired from service in 1996, and has been stored at Hiroshima Depot since February 2001, but it was taken apart in March.^{[citation needed]}

Full-production series

The production series of locomotives were delivered from 1968, with 55 built in two batches between 1968 and 1975.^[5]

The second batch of locomotives, EF66 21 to EF66 55, delivered between 1973 and 1975, incorporated a number of minor changes and improvements. Most noticeable was the extension of the cab roofs over the windscreens to reduce the deposition of abrasion dust from the pantographs on the windscreens.^[5] Some of the first-batch locomotives (EF66 1 to 20) were also subsequently modified with the "sun visor" style cab end roofs.^[5]

• First-batch EF66 3 on a freight working in June 1984
• First-batch EF66 11 in 2007
• Second-batch EF66 49 on a sleeping car service in March 2009

Post-privatization

Following the privatisation of JNR on 1 April 1987, JR Freight received the prototype (EF66 901) and 39 of the original series (EF66 1 to EF66 39) as well as the Class EF66-100 machines. JR West obtained the remainder of the machines (EF66 40 to EF66 55) – a total of 16.

Shortly after privatization, JR Freight tried out a number of new experimental liveries on its various locomotives, and one Class EF66, locomotive number EF66 20, received an experimental cream and blue livery with large "JR" logos in August 1987. No other members of the class were reliveried, however, and EF66 20 received the new JR Freight two-tone blue livery when it underwent refurbishment in October 1993.^[5]

From 1988, JR Freight retrofitted a number of its EF66s (numbers 22– 4, 26–27, 30–33, 37) with roof-mounted cab air-conditioning units.^[5]

From 1993, JR Freight started refurbishing its fleet of EF66s (numbers 1–5, 7–10, 11–12, 16–39, 41, 44, 53, 55). Refurbishment included rewinding of the traction motor coils, removal of the former JNR decorations on the front-end number plates, and repainting into a two-tone blue livery similar to that carried by the EF66-100s.^[5] Locomotives refurbished from 2004 onward, however, received a simplified blue livery, similar to the original JNR-style livery.^[5]

• EF66 20 in experimental JR Freight livery in the late 1980s
• JR Freight EF66 29 in revised livery in June 2003
• JR Freight EF66 28 in February 2007 in the later livery applied to refurbished locomotives

EF66-100

Due to increased demand, JR Freight began building more EF66s in 1989. This batch of locomotives was classified EF66-100, with locomotive numbered EF66 101 to EF66 133. The Class EF66-100 locomotives were fundamentally the same design as the EF66-0, but with slightly more modern external styling. The driver's cabs are air-conditioned. The Class EF66 100 locomotives were also built in two batches, EF66 101 to 108 and EF66 109 to EF133. The second batch differed in having rectangular headlamps and tail lamps, while the first batch had round lamps.^[5]

• First-batch EF66 108 in December 2009
• Second-batch Class EF66-119 in February 2007