However, the lowbridge type started to become obsolete when low-height chassis were developed, which used a dropped-center rear axle to enable the lower-deck gangway to be lowered.
As a result, some Atlanteans were built to a "semi-lowbridge" layout, with the front half of the upper deck laid out conventionally, and a side gangway with raised seating area towards the rear.
To facilitate this, East Yorkshire Motor Services had a number of double-deckers built with special "Gothic" roofs of severely-arched profile from 1935 to 1970, when a bypass road was opened around the Bar, to match the shape of the arch.
[3][4][5] Similarly, North Western ordered a number of single-decker buses with an unusual roof profile to clear a very low road bridge under the Bridgewater Canal at Dunham Massey.
[6] The last lowbridge double-decker to be built was bought by Bedwas and Machen UDC, a small municipal bus fleet in south Wales, in 1968.
Following its sale by B&MUDC's successor, Rhymney Valley District Council, it was operated by Stevensons of Uttoxeter and subsequently by MK Metro of Milton Keynes.