to steady themselves, broadly similar to a London Underground tube train. The trains lack toilets, as the whole NLL line takes a little more than one hour to traverse from end to end. In conjunction with the base internal configuration, the cars were outfitted with numerous modern amenities aimed at improving passenger comfort, such as air conditioning, real-time passenger information systems, wheelchair accessibility (including the facilitating of level access), and different seat moquette colours to highlight priority seating. The train is equipped with sensors to detect how many people are in each coach, and automatically adjust how much energy is expended on heating a particular carriage based upon this capacity, among other intelligent management functions that are performed. External CCTV is displayed automatically on releasing the doors via an in-cab monitor, removing the need for Driver-Only Operation (DOO) equipment such as monitors/mirrors at platforms. A somewhat similar arrangement to this had already come into use on Southern's Electrostar units. Furthermore, in the event of a passenger operating an emergency alarm, the internal CCTV is automatically displayed on the in-cab monitor, allowing the driver to view the affected area of the train, while an intercom allows the driver to speak to the passenger. Operations The Class 378 was originally intended to enter service in January 2009. This schedule was delayed by seven months as a consequence of the great recession of 2008, which had forced several suppliers into bankruptcy, resulting in a shortage of several components. This also affected delivery of the similar Class 377/5 units to First Capital Connect. As a result, the first Class 378 unit did not enter service until 29 July 2009. During 2011, several Class 378s suffered unplanned shutdowns while operating along the North London Line. The cause was found to be harmonic interference generated by passing locomotives, which occasionally traverse the line for freight movements. The problem was permanently resolved after Bombardier altered the interference tolerance settings. During January 2016, TfL announced the completion for work to extend all 57 units into a five-car configuration. In December 2018, unit 378232 was shortened back to four cars to run on the Gospel Oak to Barking line while delays to delivery of were resolved. 378206 and 378209 were also shortened to four carriages to work as temporary cover while the diesel-powered Class 172s were withdrawn. In July 2015, London Overground announced an order for 45 new Class