The solution to problem of poor road conditions is not one of technology, it is one of government policy.
When a road is built, especially in jurisdictions where finances are constrained, the road has a certain pavement structure, usually the less expensive option. However, less expensive options usually require more maintenance, especially preventive maintenance. Very few road authorities acknowledge that they do not have the means to carry out the required maintenance. Whether this happens by error or omission, the end result is the following sequence of events: pavement deteriorates, preventive maintenance is not performed, cracks appear, regular maintenance is not performed, cracks join and potholes appear, rehabilitation is not performed, and the road goes into accelerated deterioration. At this point crews are dispatched to try to patch the potholes but since this is years too late, the repairs will not last.
Additionally, because there are political interests in the administration of the infrastructure, the budget tends to concentrate in the paving of as much road as possible for as little money as possible. This approach tends to ignore the works which actually make the road stay in good condition, such as adequate drainage (which in many cases requires land acquisition), weight limitation enforcement of commercial vehicles, subdrainage to avoid elevated levels of moisture in the subgrade, and stabilization (chemical or with geogrid) of the areas of poor subgrade.
In jurisdictions where it does not snow, in my experience, (and the research can bear this out), the solution to solving the road condition problem is as follows:
1.- Use long design periods (30yrs for main roads). This results in a flatter deterioration curve, so maintenance schedules can be more flexible.
2.- Use long lasting pavements. From my personal experience, concrete pavements have yielded the best value.
3- Use a layered approach. There is a tendency to focus only on the top layer, but best results are obtained from the use of high performing bases: e.g cement stabilized, and improved subgrades, e.g. lime stabilized
4.- Ensure drainage and subdrainage performance. Subdrains, permeable bases, lined ditches, etc. are a few of the tools to be considered.
5.- Provide routine maintenance. This includes vegetation removal, culvert cleaning, ditch maintenance, etc.
The above scheme elevates the up-front cost, but reduces the maintenance significantly, and tends to avoids major deterioration for a long period. Roads such as the Mediterranean freeway in Valencia are more than 60 yrs old without major deterioration (although it has excellent maintenance), and the Airport highway in El Salvador is 20 yrs old without a need for major repairs (potholes or severe cracks).
How is this scheme of preventing (rather than repairing) the potholes achieved in practice? It requires a bold new thinking in the local engineering community, to be able to show governments that yes, the price of long lasting infrastructure is high, but the cost to society of not having it is even higher (and by orders of magnitude), since the state of infrastructure disrepair impacts industry investments, vehicle operating costs, freight prices and many aspects which noticeably increase the cost of local goods and services. If this can be conveyed to political officials, it becomes a matter of finding the appropriate financial tools, of which there are many: Public private partnerships, shadow toll roads, infrastructure banks, development banks, maintenance concessions, etc.
To sum up, you would be surprised how much policy can achieve if it is has sound technical foundations.
Let me know if you would like to discuss further.
Sergio Fernandez, P.Eng.
Sergio Fernandez M.ASCE
Senior Transportation Engineer
Sent: 08-07-2020 02:07 AM
From: Kelvin Marumba
Subject: LONG-TERM SOLUTIONS TO POTHOLES
My name is Kelvin Marumba and I am working as a Research Scientist in Zimbabwe. The major problem on our road is dealing with the issue of unbearable potholes and I am sure this is also an issue in other developing countries. I am seeking assistance in different types of ways to solve this issue or rather solutions and methods I can use to patch these potholes and get a longer lifespan. Which mixture of materials can I use to patch them up or what materials can I look into or research into? We are trying to avoid expensive methods and have a temporary solution with a longer lifespan for patching up the potholes. I look forward to your favorable responses.
Kelvin Marumba Aff.M.ASCE