Motorways: layout and number of carriageways
|Location||National Archives (see all files stored here)|
|File base||Series MT, subseries MT 95|
This file contains discussion of two lane versus three lane motorways with regard to traffic capacity and, more frequently, safety. In particular this seems to be because high-profile people at the Ministry had noticed that on two lane motorways slow vehicles overtaking even slower vehicles (at a time when some lorries could manage little more than 40mph) would block the entire motorway for a considerable distance. They regarded this as a hazard that could be overcome with a third lane, and the alternative was that - if rear-end shunts from faster traffic became a problem - a general 50mph limit might have to be applied to two-lane motorways. Experts in the department argued that this was not the experience of any other country and that the UK was unusual in having a considerable milage of three-lane motorway at all.
An examination was also carried out of the merit in building two-lane motorways ready for later widening. It was deemed unsuitable as a policy because it was cheaper overall to build three lanes in the first place than it was to build the earthworks and bridges, and then later modify the drainage and pave a third lane. Design policy at the time was that if a need for three lanes was envisaged, no matter how far ahead it was, the third lane would be provided at the time of construction.
The Highways Executive Committee eventually prepared a report titled “Layout of Motorways” that set a standard response to the various arguments for and against building three lanes from the start and, for the most part, defending existing policy on the matter.
People with camera copies
Chris Marshall has a copy of the final report but nothing else.