How do you make a road?

What goes into building a road?
28 May 2019

Interview with 

Julian Lamb, Highways England




How do you go about actually making a road in the first place? Katie Haylor put this to civil engineer Julian Lamb, deputy project director for the A14, working on behalf of Highways England. Donned with a whole load of personal protective equipment, they drove down to a section of the construction works, to take a closer look at what - literally - goes into a road...

Julian - We're halfway between two of the bridges that we have on the scheme. We are constructing a dual carriageway here with three lanes in each direction so you can see the different stages of construction.

Katie - Underneath the black layer that I can see that I would recognise as a road surface, you’ve then got a pretty thick, brown, grey, layer. What happens under that then?

Julian - The concrete layer is founded on a ground improvement layer. It's a gravel and laying that as your foundation to the road pavement that we're stood on.

Katie -  Before you start building what kinds of factors would you need to take into consideration?

Julian - A great deal of consultation is necessary and in fact a scheme of this size is subject to a development consent order. Some of the main things are obviously the landowners that you are having to compulsorily take land from, the heritage -  so there's an archeological mitigation that we have to do  - and also environmental and ecological mitigations that we have to do in advance of being able to access the site, to carry out the work that we need to do and in fact the borrow pit that we came past before we found some woolly mammoth tusks and woolly rhino skulls.

Katie - So what about ecological considerations? Because when you're building a road, arguably you're inconveniencing people for their construction time, but I guess you could also be inconveniencing wildlife, right?

Julian - Yes that's very much the case and we've got some protected species that we've been looking after here. There's reptiles with the Great Crested Newts and we've had extensive areas of amphibious fencing that we've had to put in as a temporary measure and also as part of a permanent measure for the scheme. Also got some water voles, and other protected species, and we have been creating some new habitats especially for the water vole which meant that we had to trap them and keep them in a safe place while we were building the new habitat. We've also as part of the scheme we're reintroducing twice the amount of trees that we're removing, we're planting around a million trees as part of the scheme. Our aim for the project is to become biodiverse net positive.

Katie - Once you've done all of that, literally how do you make a road?

Julian - The first thing we have to do is to safeguard the site, and so we have to create a boundary to make sure that it's clear where our site is and where the members of the public can be. There are a whole series of utilities that we have to divert as a necessary part of the scheme. But once you've got the footprint, we've got a number of structures to build, some bridges to take existing side roads or farm tracks and take them up out of the way of the new A14.

Katie - You're having to consider people who need to use the area near the new road all the time that you’re actually building it right?

Julian - Yeah we have to maintain existing accesses, so there are a number of side roads that we have to construct. We've got 35 new structures to build on the project and we're having to do some modifications to another 35 on the scheme. We have to make sure we look after the water, so the first thing is to do pre-earthworks drainage and that's to provide a cut off, it might be a V ditch, it might be a filter drain with stone that takes water down into an underlying pipe, to make sure that we've cut the water off before it gets into the main trace.

Katie - Because earlier you said to me that water is the enemy when it comes to building a road. Is that right?

Julian - Well not so much the enemy, but we have to make sure that we've made provision in to how water is going to land on the surface and how it's cast to the side. So we have to just manage it during the course of the project.

Once we've done that we then set about doing the bulk earthworks. Now normally on a scheme you would try and balance your cut areas - where you're going below the existing ground - with your fill areas where you're going above the existing ground. What you don't want to do is to have surplus material you’ve got to dispose of and you don't particularly want to import material. That's the normal situation, because we are in a floodplain this project is built on an embankment, so we have to import material which we're doing from locally sourced borrow pits along the trace to keep haul distances as short as possible. That saves on money, keeps the haulage off the existing road network.

Katie - I guess you also have to consider the environmental impact of actually doing the work. If you're accessing materials locally you've got less stuff to haul which means you are using less petrol, diesel or electricity to actually move that stuff.

Julian - That's very much the case. We then do post-earthworks drainage which will sit linearly with the project in the centre reserve or in the verges of the pavement.

So we're now in a position that we can start building the road. It's the first granular layer of material that we start with which is about 600 millimetres thick. We then have a cement bound concrete in two layers, which is about 350 millimetres thick and then we have an asphalt pavement that sticks on top of that which is about 180 millimetres thick, lade in three layers. Finishing works including safety barrier, the centre reserve barrier, lighting, road signs, gantries, all the telecommunications, so there's a few other jobs that we have to do before we get the white lines down. We like to leave that to the end, to make sure that it's fresh and clean for opening to traffic.


Katie - We can see in the distance the old A14.

Julian - Yeah. It's actually running today but because it's reached over capacity it's quite often stationary and that's the whole reason why we're here.

Katie - To me it smells a bit like a petrol station but I've probably not got a very educated nose, is that bitumen?

Julian - That would be the bitumen smell from the asphalt-laying process, yes.

Katie - It's not my favourite. Do you like it? You must come across it quite a lot.

Julian - Yeah we do and I’ve become accustomed to it. I quite like it actually. There's three materials in the industry that really bring on the closure of the project which is top soil, concrete and asphalt. And with asphalt you can really smell the progress.


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