What makes a road?

There are vast differences in types of road – a hairpin bend on an alpine pass is (literally) a long way from a cobbled lane in an English country village. The materials and design vary widely, of course, depending on what is appropriate for the application.

Tarmac and asphalt
There’s an interesting look at the idea of the road itself on cycling blog the Inner Ring. From the earliest history of roads to today’s asphalt, there are several eye-catching points, including the comparison of $25,000 per mile “chip seal” or “tar and chip” method of construction with the $350,000 per mile cost of asphalt.

And the impact of the seasons is as keenly felt in Europe as it is in the UK:

Other parts of Europe see winter damage and subsidence. Some Alpine roads get smashed by coachloads of tourists and subzero temperatures, they are relaid every year. But away from the resorts the frost is left to crack and shatter the road.

Stelvio Pass by Damian Morys Foto, on Flickr

Aggregates
There are also some diverting thoughts out there on unpaved or unsealed surfaces. Where a road experiences low volumes of traffic, it has been found that maintenance costs for gravel roads often exceed the maintenance costs for paved or surface treated roads when traffic volumes exceed 200 vehicles per day.

So for small community developments, and some longer private driveways it may make economic sense to specify aggregate surfaces.

Curvy Rails by Ed Thomes Photography.com, on Flickr

Concrete
In Belgium the betonweg or concrete road is found in rural areas. Large sections of concrete are separated by small gaps, partly for drainage but also to let the material expand on a hot day, to avoid the surface buckling under expansion.

Concrete road by LHOON, on Flickr

Concrete block paving is typically used for private driveways, car parks and hardstandings, as well as pedestrian areas, squares and shared-use urban spaces, and provides a surface that is durable and easy to maintain, while permeable installations can ease the pressure on urban drainage systems.

image by crinklecrankle

Cobbles
Ornamental cobbles and setts are still used in historic residential areas and town centres, while some agricultural tracks are still surfaced with original stones.

The simple but useful Paving Expert site has some design guidelines for cobbled paving construction. The Building Conservation website also has a very useful article on the best ways to design and specify cobbles and setts in historic townscapes.

Cobbled Street at Dinan by wwarby, on Flickr

Tags: Pavements and roads