Parent image: East iE parked at Nishi-Funabashi Station in 2017, at the terminal of the Musashino & Keiyo Lines.
The JR East E491 series, nicknamed the East iE, is a non-revenue train specially designed to inspect the tracks and electrical connections to the trains. Only one set was made in 2002 to replace multiple older trains built for the same task. It services electrified lines under the authority of JR East (hence the nickname) and is housed in Ibaraki.
Floodlights built into a special window on the side of the one of the cars:
Other cars built for inspection purposes can be coupled with the East iE. For example, cars designed to test tunnel clearances or to carry additional testing equipment.
East iE with its lights on:
East iE has two sister trains. The East i, which is an inspector train built for the high-speed JR East Shinkansen lines, and the East iD, which is an inspector train built for the non-electrified JR East lines. The D stands for its diesel engine. All three trains are different models built at different times, but have the same white with red band livery.
The East iE logo painted on the side of the train:
