Wednesday, 6 June 2018

Concrete cycle-paths. Smooth, maintenance free and generally preferable to asphalt

A lot of the cycle-paths in this area are made of concrete rather than asphalt. When I first moved here  it seemed a slightly odd choice because concrete is a more expensive material. I was surprised that we were getting the premium product while drivers on roads alongside those cycle-paths had the "cut-price" asphalt (immaculately laid, mind you).

The advantages of concrete have become more clear with time and were reinforced by a representative of a company which builds cycle-paths who I met a few days ago at the opening of a new path in Assen. The main advantage is that once laid, concrete cycle-paths generally require no maintenance for 30 years. We've only lived here for 11 years, but while the city has been diligent about fixing problems which occur on the asphalt paths, sometimes before they're really problems at all, and in some cases three times while we've lived here, none of the concrete paths have required any work at all so far as I can tell. For this reason I'm inclined to believe 30 year claim. Another advantage is that relatively little preparation of the ground underneath the cycle-path is required, making these paths less labour-intensive to install than would otherwise be the case. Obviously the ground underneath should be flat, but that can be sand and a 20 cm thick layer of concrete is then enough to spread the load and withstand damage without the same multiple layers of support as asphalt paths require.

There are concrete cycle-paths in this area dating from when we moved to this area which still look exactly as they did when we first saw them except that the bright colour has faded a bit. Others which already looked faded when we first came to live here also remain perfectly smooth and pleasant to cycle over. Even when there are trees nearby, these paths appear to be so completely immune to the problem of root damage.

Cycle-path which is at least ten years old. Next to trees. Perfect.
A brand new cycle-path in Assen, to be covered in the next blog post
A cycle-path in Assen which is around ten years old - surface is still perfect
Another older path, next to trees. Perfect surface The gap was cut into the path after it was laid in order to allow for expansion. There is difference in height and you can't feel this as you cycle over it.
Even where paths are also used by occasional motor vehicles (this one is only a golf kart, but tractors are quite common on rural paths) they're very resilient.
There are many hundreds of kilometres of paths like this in this area now and they're all delight to ride on. This one is in a rural area for recreational use, hence less width than a busy urban path. Note also the unsurfaced road alongside for motor vehicles. This is how routes in the countryside are unravelled.
Paths like this in the countryside are extremely popular with all cyclists who like to ride a bit further and faster.
Rural but a main route alongside a fairly busy road. No damage here even at the entrance coming up where motorists have to drive across the concrete cycle-path.
By comparison, even with good asphalt cycle-paths, root damage is a constant threat. In this case it's marked for repair. The repair happened very soon after the photo was taken and before the path became unpleasant to use, but it simply wouldn't have been necessary with concrete which is more expensive in the first place, but cheaper in the long term.
How these paths are constructed
The good concrete cycle-paths are poured on site and made in one long continuous pieces, usually 300 m in length. Where they join after each 300 m, there are a few cm of slightly soft asphalt to fill the gap and allow for a little movement. Every 3-10 metres (this seems quite variable) the concrete is cut after it has cured to allow for some movement. The surface is textured so that it provides grip for your tyres even when icy.
The concrete is 20 cm thick
Ground preparation is nothing more than making a level surface and applying a layer of soft sand. You can also see in this photo where the path was cut every few metres. Note that the zoom lens makes the distance between cuts seem far less than in reality. Note that when the cycle-path was completed the vertical sides were covered up. The second photo from the top shows the same cycle-path a few weeks after it was completed. There is now no vertical drop at the side.
This textured surface provides grip for bicycle tyres in any weather.

An alternative type of concrete cycle-path
Recently, the first stretch of a new fietssnelweg (cycling motorway) came into use between Haren and Groningen. It's a boon for commuting cyclists because it provides a decently wide path taking a very direct route along the canal which avoids traffic lights and junctions so is faster than any other route over its 3.5 km length. However, while this is a concrete path it's constructed in a new way and I don't think it's quite the same quality as that which is usually used.

Instead of being made of one piece of concrete poured on site, the Haren-Groningen path is made of pre-fabricated sections which have been laid against each other. They are of a design which interlocks and is supposed to be stable and I hope the sections won't come apart and create gaps, but as it stands there's a perceptible bump every two metres along the path. Mostly the sections are fitted very well into each other but in some cases it's possible to see nearly a centimetre difference in height between successive concrete sections.

This new method of constructing paths presumably has some advantage or it would not have been used. I have fears that it simply won't prove to be both durable and of high quality. However as it only opened a few weeks back we will have to wait and see.
In the worst case the gaps between sections have almost a centimetre difference in height
The sections are four metres wide and two metres in length. Running over the gaps every two metres means that you will notice them quite often if some of them are less than perfect. It's certainly not unpleasant at the moment, but I'm concerned that it will get worse and then anything which rattles on your bicycle will rattle annoyingly.
There are 3.5 km of this and it does make a very efficient cycle-path. In any other country in the world, a direct cycle-path like this would be seen as a miracle - especially when this new high quality route is parallel with four other very good, safe and convenient routes into Groningen from the South within a few kms, all of which we've taken with study tour particpants in the past: a very pretty and pleasant countryside route on the other side of the canal (the pleasantness of which excuses this more direct route being tainted by motorway noise - we're given a choice), another route a bit further to the right of this photo which passes the airport and a third which isn't all that far away from the motorway on the left but which has a few too many traffic lights for my liking and finally another route even further to the left which I used to take to reach my work in the SE of Groningen.
This video shows a short part of the Groningen-Haren path:


Please also see an updated video showing the entire route, including all the faults with this path.

Good paths are good. Not all concrete is the same.
Note that the good examples above are of concrete paths which are laid in one piece, are wide, have thick concrete which is resistant to damage, they're textured for grip and they do not have vertical drops at the side of the path. All of these aspects are important. Cycle-paths should not be constructed out of separate tiles between which there is always a bump or with thin surface layers which are guaranteed to crack. They should not have vertical drops at the sides, should not be too narrow for people to ride side by side. Corner radii should be generous, care should be taken to keep cyclists out of the "door zone", sight lines need to be long so that collisions can be avoided and priority at junctions must be obvious so that all parties know what they should do. Please read other cycle-path blog posts for other details of good design.

No comments: