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Determining the carrying capacity of roads

It goes without saying that roads play an important role in the daily transportation of people and goods. Due to the heavy use that Australian roads are subjected to, it is important for these roads to be properly maintained over the years. Indeed, proper road use will result in longevity and reduced maintenance costs.

One of the biggest factors that determine the longevity of roads is carrying capacity. This is a measure of the load that the road can safely bear over time, without causing road damage or failure. Carrying capacity is determined primarily by the following factors.

1. Pavement construction

Pavement construction refers to the state of the actual surface of the roads, as well as all its edges. It is perhaps the most important element of carrying capacity, as it is directly impacted when a road is overly/poorly used. Without considering pavement construction, roads can become damaged via portholes and uneven wear and tear.

Pavement construction is determined by the actual materials used to design the road, as well as the thickness of these components. For example, roads that are made of tarmac have a specific limitation on the tonnage of vehicles to be used. The pavement construction will determine the maximum load and weight of such vehicles before they can pass through the road.

Therefore, when determining carrying capacity, the limits of the road surface should be carefully considered.

2. Traffic volume

How heavily a particular road is used (traffic flow) will also determine it's carrying capacity. Indeed, heavy traffic flow results in greater wear and tear and may impact how much the road can sustain traffic. Busier roads often require a higher carrying capacity regardless of the size of vehicles passing through. In fact, when determining carrying capacity of roads, a higher traffic flow along the corridor typically symbolises a higher capacity.

In some cases, it is useful to break down traffic volume into individual vehicle capacities so as to come up with a more accurate determination of the road's carrying limits (capacity) under optimal levels.

3. Load tonnage

The load being upheld by the road pavement also directly impacts carrying capacity. Different vehicles have varying loads, and the average weight of each vehicle class should be determined when calculating carrying capacity. For example, interstate highways that shoulder both trucks and smaller-sized sedan vehicles will experience load tonnage that is a mix of both types of cars.

Civil engineers will typically analyse the traffic flow as well as loads of each type of vehicle and determine how much the load will impact carrying capacity. For more information, contact your local structural engineering company.