Post by Dr. Stephen Watkins
Motorway noise and motorway land-take could be addressed by enclosing the motorway. The Dutch have developed thick Perspex sound barriers with which they line motorways. It is possible to stand in a children’s playground in Rotterdam feet from the main motorway to Brussels without hearing any noise. Dutch use the barrier only as a noise buff, but the lower parts of it could be covered in climbing plants and the upper parts of it in solar panels which could provide 1,800 hectares of solar panelling. The necessary funding could be raised partly by the electricity generation and partly by capturing the land value benefit of making it possible to develop housing much closer to the motorway.
The motorways could be roofed over. In the UK a number of problems could be solved by roofing over the motorways with three tiers of roofing.
The first tier of roofing would carry a light railway and moving pavements for pedestrians and cyclists.
The next tier could be a linear city. Formed of two terraces of housing facing each other across a street, with each house being 20ft wide, this could provide 1,200,000 new houses, all of them with access to greenspace above them on the third tier of the roof and to public transport and walking/cycling facilities below them on the first tier of the roof
The top tier could consist of forest, wildflower meadows, or parkland. Assuming each of these options takes up a third of the 2,300 miles we could have over 4,000,000 trees, 1,500 hectares of parkland, and 1,500 hectares of wildflower meadow.
This scheme could be implemented without changing the way the motorway functions as a highway, but it could go further and be combined the conversion of motorways into railways. Express vehicle-carrying trains could replace the highway function of the motorway within two of its lanes and a small part of the capacity of a third. With a typical three lane motorway and hard shoulder four tracks could be laid, two of them exclusively used by rolling motorway trains, one of them carrying some rolling motorway trains but mainly used for a new national multimodal freight network, and the fourth track being available for a new national high speed rail system. A national high speed rail system and a national multimodal freight system are both badly needed but currently thought to be unaffordable. This option makes it possible to build them much more cheaply.
The rolling motorway would consist of one lane given over to a pick-up service calling at all access points, and a second to a faster service calling at all service stations. It would be necessary to develop systems of rapidly loading and unloading vehicles onto these trains.
With the bulk of the motorway system converted into rolling motorways it would be possible to envisage extending the motorway system by putting rolling motorway services onto existing lines (although clearance of the loading gauge would be needed) or by reopening closed railways with a rolling motorway forming part of the economic case for reopening. They are many rural areas which have aspirations to restore their railway service and which are also not served by the motorway system.