Railway tracks could soon be converted into roads, according to inventor Peter Coates Smith, who has a plan involving waste car tyres.
Some of the oddest sounding ideas have become mainstream technology - two tin cans and a vacuum cleaner became the hovercraft, while brick-like portable phones are now the ubiquitous mobile.
So inventor Peter Coates Smith's plan to turn rail tracks into rubber roads may not be as daft as it sounds.
It was certainly attracting a lot of attention at a public launch last month, with more than 100 civil engineers joining representatives from local authorities, transport executives and lobby groups to see a short demonstration track laid in a rail freight yard in Corby, Northamptonshire.
The basic concept is an environmentally friendly one: taking old car tyres, shredding them and re-working the material to form modular construction panels for a road bed and surface. And this technology has been proven over the last decade by Coates Smith's company Holdfast, with level crossings made from the same materials.
Crumb rubber from shredded tyres bought in by the company is mixed with a proportion of grit and bre before a cold-setting polymer binder is added.
'You then need just 44 minutes in a 400t press and the elements are ready, ' says Coates Smith.
Coates Smith claims the rubber is long lasting and hard wearing. He also says it gives a better seating around rail and tram tracks than conventional asphalt or concrete, with less danger of spalling or cracking, especially in places where severe freeze-thaw cycles might take a toll. And it fulls skid resistance requirements for Network Rail.
But his rubber roads idea is proving more controversial.
This involves using enlarged versions of the panels - and a newly devised fixing system - to embed existing railway lines, forming a single-width carriageway for each track.
The new panels, called Holdfast Rubber Highway, will be longer at up to 5m in length, and fit both between the rails and on the outside of them.
The panels sit on two longitudinal aluminium strips bolted to the old sleepers.
These were devised because the irregular spacing of sleepers prevents direct bolting of the panels. Each panel is firmly connected to the next with a male and female hooking type of connector, and another connector keeps the outer cess panels in place on the rails.
Coates Smith's idea for the panels is to use them along stretches of disused railway line where they would create a single-lane road along the track, which he believes could provide alternate routing for cars during peak times or maintenance periods and therefore relieve congestion.
'There are hundreds of stretches of such track in the UK, and some in useful positions running into the centre of cities, ' he says.
He suggests that the traffic, which would usually be limited to cars and light vans, could be run in between intermittent tram and light rail services, which would also use the track.
The scheme is supported by government-funded recycling organisation Waste and Resources Action Programme (WRAP), which has put £250,000 towards funding the 300m trial section.
With whole tyres and even processed tyre waste already banned from landll, it is important to find new uses for tyres, says WRAP materials project manager Steve Waite.
But a number of doubts over the scheme have been raised.
Many of the engineers present were unsure about mixing light rail with trafc and about the limitations of the single-lane passage, without any paving between the two rail tracks.
But many of the engineers at the launch were not dismissing it out of hand.
Victoria Jones, construction & utilities manager for London Trams at Transport for London, thought the system deserved more investigation, though more for street embedding of lines.
Another suggested use for the system is to pave rail freight yards, allowing them to be used for road vehicle parking during periods of low use.