Highway Jottings-9

Finding solutions begins with the correct diagnosis, irrespective of the nature of the challenge and domains.

Potholes are a big pain for road users of all vehicle types.

A recent report in Mumbai’s Mid-Day by Prajakta Kasale was spot on. The Bombay Municipal Corporation (BMC) advised its engineers to inspect roads for spotting potholes on two-wheelers and NOT on four-wheelers!

Abhijeet Bangar, Additional Commissioner of BMC, took a practical approach. He instructed his engineers to inspect roads for potholes on bikes instead of four-wheelers daily.

Why bikes?

Bangar’s rationale is pure common sense and ingenious. He says, “The first thing is that four-wheelers avoid potholes and bumpy roads more easily, and on bikes you CAN GET A BETTER IDEA OF ROADS. An entire stretch is visible by bike.”

Adds: “There is no chance to develop a one-meter pothole in a single night. On the first day, a pothole is not more than six inches and if it fills up on that same day, it won’t create a bigger pothole later. So surveillance and early action is the key.”

Pothole management is not rocket science but deserves the same attention that NASA or ISRO scientists show in their missions. Why is it so important? From the macro perspective, the Ministry of Road Transport & Highways (MoRTH) lists potholes as contributors to road accidents. Government data reveals that potholes’ contribution in percentage terms between 2021 and 2022, for which input is available, was a whopping 22.6% for the country.

While BMC Bangar prescribes the most effective spot check to rectify the anomaly, the National Highways Authority of India (NHAI) is toying with adopting new technology that will “self-heal.”

Yes, you heard it right. Self-heal. For India, such an idea is novel indeed. These ingenious and unconventional methods have the potential not just to improve durability but also to revolutionize how we address the pothole challenge. Imagine asphalt that can heal itself once it is damaged. How do asphalt roads function? They are a mixture of gravel and sand held together by bitumen, which melts and develops cracks that gradually become big potholes.

For road maintenance teams, asphalt is the go-to material for road surfaces because it is easy to use and often porous, which absorbs noise and makes the roads quieter. However, it is not durable.

With India continuing to top the dubious chart of the highest number of road accidents globally, road maintenance assumes greater importance.

Erik Schlangen, a materials scientist at Delft University in the Netherlands, has introduced a game-changing technology. He mixed steel fibres with asphalt to make it conductive and ‘self-healing.’ Though 25% more expensive than the conventional method, this innovative technology has the potential to significantly increase the lifespan of roads, thereby reducing the need for frequent maintenance.

Ana Maria Rodriguez-Alloza and a group of engineers drawn from various European nations writing in a research paper titled Consequences of long-term infrastructure decisions — the case of self-healing roads and their CO2 emissions, draw attention to the climate change angle.

“Asphalt healing is a scalable technology worldwide. As reported by Bosisio et al., a mobile device was applied for this purpose in Canada in 1974.

Although the experience showed promising results, awareness of sustainable and ethical use of natural resources and global concern about climate change were not as important as today. Additionally, the tools for life cycle assessment were not as advanced as they are today.

In short, although it was technically suitable, there were neither sustainability reasons to prompt the spreading of this technology nor a method to accurately evaluate the environmental benefits or disadvantages of this pavement maintenance strategy.

This study incorporates steel slag as aggregates, providing the asphalt mixture with better susceptibility to microwave radiation, which might reduce the micro-wave-heating technologies’ energy consumption. To implement it at the field scale, it would only be necessary to add steel slag as an aggregate in the new asphalt and machines that can heat the pavement. Steel slag as an aggregate already fulfils the current specifications and is nowadays used for its excellent properties, but without taking advantage of the self-healing properties. And the machines needed already exist to repair potholes and small areas of ground thawing.”

The authors point out that “nowadays, asphalt pavement researchers are demanding investigations at the field scale for self-healing asphalt technologies to prove their practicality, sustainability, and cost-effectiveness. However, before implementing this new promising sustainable technology at the field scale, life cycle assessment analyses are urgently required to support this technological innovation, and this is exactly the novelty and value of the present study.

In this study, we aim to quantify the climate change consequences of road construction and maintenance decisions, as they are long-term, large-scale infrastructures.

This innovative technology for conserving roads is still under study; hence, the environmental benefits of self-repairing pavements have not been evaluated and quantified with precision compared with traditional conservation techniques.

For this purpose, the researchers undertook a hybrid, input-output-assisted Life Cycle Assessment to determine whether this new technique of in situ conservation is beneficial from a sustainability perspective.

As mentioned earlier, cost is a critical element. Plus, “the investment in roads has a time horizon of several decades. Predicting the change in an economy’s technological coefficients would be a significant disadvantage of a carbon assessment. Such predictions for a time horizon of several decades introduce additional uncertainty into the calculations,” emphasize the researchers.

Hence, they used historical input-output data from 1971–2015 to investigate the carbon emission consequences of infrastructure decisions for self-healing or conventional roads within this time horizon.

The results were revealing. The researchers found that self-healing roads delivered not just lower emissions over their lifecycle but also significantly lower costs over their lifespan compared to roads constructed with traditional conservation techniques. This underscores the potential cost and environmental benefits of self-healing roads, which could be a game-changer in our road maintenance strategies.

That’s not the end of the story. For both case studies, capex (capital expenditure from construction activities) contributes more to carbon emissions during their lifetime than opex (operational costs): 60% for conventional roads and 70% for self-healing roads. Building roads has a higher impact compared to maintenance operations.

Like any country, India is cost-conscious, so, unsurprisingly, the government is evaluating the cost-benefit analysis of installing self-healing roads to combat ballooning road fatalities.

A group of researchers with Kaffayatullah Khan at the lead succinctly puts the facts thus:(2) “Asphalt is the most often used material in the road-building sector. Therefore, the revolutionary approaches created for the building and upkeep asphalt road pavements offer a huge promise for road improvement. Specifically, self-healing time can bring about significant modifications in this sector, for example, decreasing maintenance requirements, depletion of natural raw materials, interruption of traffic flow and CO2 discharges at maintenance time, and improving road safety.

Conventional maintenance requires equipment and natural materials, partial or entire road closure, and human intervention with field workers, resulting in traffic disruption, congestion, and increased greenhouse gas emissions. In contrast, a self-healing pavement should be capable of fixing damage independently or with minimal assistance.

TAILPIECE: The pothole problem dates back to the Roman times. The American Journal of Archaeology reports that archaeologists surveyed Pompeii’s streets in 2014 and found 434 spots of iron on the paving stones, suggesting that liquified iron was used in road repair. (3)

“Pompeii, in particular, had some pretty serious road problems. Most streets in the bustling seaside city were paved with silex, a cooled lava stone that wore away relatively quickly, leaving ruts from wagon wheels. The city’s narrow streets were also used to deal with sewage, which didn’t help, causing pits and cavities to form in the stone.

But the disruption of full-on road repair or replacement probably wasn’t acceptable to the Pompeiians. “One option for repair, complete repaving in stone, was a difficult and expensive endeavor that might block important through-routes in a city for months,” the authors suggest.

The team believes that because of this, the Romans devised a novel solution: dripping molten iron into the ruts and pits.

In some cases, they added stone or ground-up ceramics to the iron. But the iron is only found on main thoroughfares where roadwork would have been a major hassle. On smaller side streets, crews replaced the stones over time.

One question is whether iron was plentiful and cheap enough for such repairs. The researchers believe the answer is yes. By the late 1st century A.D., Rome was already producing 550 tons of iron annually from deposits in recently conquered Britain, from an area in the southeast of the island called the Weald. Large amounts of iron were being mined in other areas as well. And the paper suggests that traders may have used iron slag as ballast in their ships. When they reached a port, they could sell the slag, which still contained a large percentage of iron.”

Dennis Lynch, a civil engineer turned writer with a passion for history from Rutgers University in New Jersey, finds “one glaringly huge difference between Roman roads and modern roads that has only been alluded to so far. That difference is the traffic itself. Roman roads did not have to deal with cars and semi-trucks driving as fast as they do now. “

Regarding how potholes develop, researchers Cèsar Carreras & Pau De Soto (4) claim that “a standard wagon would weigh around 3,000 pounds (1.36 tonnes) and could travel around 10 miles a day at normal speed on plain terrain. Meanwhile, modern cars weigh an average of 4000 pounds, and fully loaded semi-trucks are over 20,000 pounds of weight (9 tonnes)! The average car alone weighs more than a fully loaded wagon!

The average US interstate road allows 60 to 70 miles per hour. There are plenty of drivers who drive faster than that. Imagine a legion of 20,000-pound semi-trucks driving 70 miles per hour over a road. If one compares that to a convoy of 3,000-pound wagons driving at 10 miles a day, it can easily be seen that Roman roads are not special compared to modern roads. Modern roads take a heavier beating and still provide a relatively reasonable and economical way to transport things worldwide.”

United Kingdom Prime Minister Rishi Sunak pledged to tackle “the scourge of potholes” by funding £8.3bn for local road maintenance in England. Rival Labor party sarcastically remarked that the moon’s surface is “silky smooth compared with the UK’s roads.” Interestingly, British potters who could not afford clay would often steal it from the Roman roads as they were built on top of a heavy layer of clay, causing deep holes in the road surface.”

Like inflation, tax and death, potholes are universal! No discrimination.

References:

(1) Ana Maria Rodriguez-Alloza et al 2019, Environ. Res. Lett 14 114040

(2) Khan, Kaffayatullah, Ahmad, Waqas, Amin, Muhammad Nasir, Khan, Suleman Ayub, Deifalla, Ahmed Farouk and Younes, Mohammad Yousef Mohammad. “Research evolution on self-healing asphalt: A scientometric review for knowledge mapping” REVIEWS ON ADVANCED MATERIALS SCIENCE, vol. 62, no. 1, 2023, pp. 20220331. https://doi.org/10.1515/rams-2022-0331

(3) https://www.smithsonianmag.com/smart-news/pompeii-fixed-potholes-molten-iron-180972203/

(4) Carreras, C., & De Soto, P. (2013). The Roman Transport Network: A Precedent for the Integration of the European Mobility. Historical Methods: A Journal of Quantitative and Interdisciplinary History, 46(3), 117–133. https://doi.org/10.1080/01615440.2013.803403