wider footbridge, which was provisioned with both lifts and escalators, along with special event stairs to facilitate excellent access to the nearby Murrayfield Stadium. In addition, various retail outlets were established in the new building; approximately 15 per cent of the new concourse is allocated to retail space. More minor changes that were incorporated into the design include the installation of energy-saving lighting and modern passenger information systems, while the platforms were resurfaced and the installation of longer canopies, which is aimed at providing better protection from bad weather conditions and increase boarding speeds. One particularly unusual feature adopted was the ETFE Air Filled Pillow roof, which uses pillows of transparent ethylene tetrafluoroethylene (ETFE) material filled with dehumidified air which is cycled via a central air pump; it offers a reduced weight while also being an intentionally sacrificial element of the structure in the event of an accident or major incident. Some design changes had to be incorporated before planning permission would be granted; in one case, the proposed copper cladding had to be replaced by a black granite and zinc counterpart. During May 2012, construction work commenced at the station, initially focused upon temporary station alterations to create space for the new concourse and the undercroft below it. Where possible, items were partially built off-site before being transported and moved into position using large cranes, such as the steelwork for the new footbridge, which minimised passenger impact and was considered to be more safe. According to Network Rail's project manager Tom McPake, work typically involved no disruption to train services as it only required rules of the route possessions; keeping the station operational throughout was described as being the main challenge. Reportedly, the redevelopment scheme had been completed both on time and within the assigned budget. During December 2013, the Minister for Transport and the Islands Keith Brown formally reopened the station, marking the official completion of work. Cleanup work, such as the demolition of the old footbridge and lifts, continued until April 2014. 1924 accident On 28 July 1924, a passenger train ignored a stop signal and collided with a second train at the station. Five people were killed. According to the report written by Colonel J. W. Pringle for the Ministry of Transport, the accident was a SPAD (Signal Passed at Danger) caused by the position of the driver, his misreading of the signal, and his not