Solution for faster, more affordable construction of rural roads in emerging markets

COLPISTE is an affordable soil stabilisation solution that, when applied to existing tracks in rural areas, creates a consistent and stable surface on which a thinner layer of asphalt can be applied to create all-weather, reliable, paved rural roads.

COLPISTE was developed in Africa by COLAS, a French private company, that has prioritised sustainability, affordability, and use of local providers in its implementation model.

• Compared with traditional ‘reference’ solutions for protecting dirt rural roads, the COLPISTE solution results in 70% less CO2.
• Applying circular economy principles, COLPISTE uses 75% less aggregate than traditional methods and applies in-situ recycling to reduce waste of on-site materials.
• COLPISTE is 40% cheaper than a traditional solution for protecting rural roads and 10% more expensive than a dirt road construction.
• COLAS will outsource 30–40% of the project activity with COLPISTE to local providers.

COLPISTE has already been applied to nearly 100 km of rural road in Senegal, Africa and was one of the top 5 solutions selected by the Global Infrastructure Hub and its eight MDB partners in the Call for Submissions for Sustainable Roads in Emerging Markets.  

Need and use case for the technology

Many rural tracks are located in areas with extreme climate conditions that may vary from very dry in summer to very wet in wet seasons and winter. These rural tracks may be impassable for days or weeks at a time. Yet, the tracks are critical to provide access for residents and the movement of goods. In Sub-Saharan Africa, for instance, more than half of roads are unpaved and less than half of people have access to any type of all-weather road, according to the African Development Bank.

However, asphalting under these conditions is difficult. Wet and dry soil alike make for challenging construction, often requiring thick (and costly) layers of asphalt – which also consumes large amounts of asphalt and gravel.

These factors create the need for an affordable and effective solution to quickly and sustainably construct rural tracks that are adapted to the local traffic, will be reliable in all weather, and will require less refurbishment and maintenance.

Overview of the technology

COLPISTE is a construction solution developed by COLAS to support the establishment of paved rural roads in emerging markets and developing economies (EMDEs).

These countries present the following main characteristics:  

• A growing demand for mobility, to contribute directly to economic development and the wellbeing of populations  
• A large scale of uncoated rural roads.

The COLPISTE solution transforms rural roads into sustainable assets by applying a frugal and innovative construction technique that is based on high-efficiency machinery and in-situ treatment of materials. The solution consists of a soil stabilisation agent, cold emulsion, and asphalt processes that minimise carbon emissions in production and construction.

The result is rural roads that:

• Are resilient and serviceable whatever the weather (even in wet periods) thanks to a waterproofing layer  
• Offer improved durability over seasons  
• Offer improved comfort, trafficability, and grip – and therefore security – for road users. 

“We take a disruptive approach to address the multitude of issues faced by emerging economies in developing rural transport infrastructure that on one hand is exposed to strong environmental and usage constraints like wet weather and overloaded trucks, while on the other hand is critical to connect people and regions where there is low capacity for construction and maintenance.” – COLAS 

Overview of the company

COLAS is an international company with a mission to design, build, and maintain transport infrastructure worldwide and an ambition to be the world leader in innovative sustainable mobility solutions. COLAS employs 60,000 people, works in 50 countries, and has an annual turnover of €15.5 billion. The company has a 90-year history in Africa, where it works in 12 countries and employs 6,500 people, including in a research and development centre located in Morocco. 

Transformative outcomes of the technology

COLPISTE was developed with a focus on maximum impacts for underserved rural areas and populations. As noted above, it uses technology to reduce material use, maximise recycling, reduce carbon emissions, and provide economic benefits. 

COLAS has also proven that COLPISTE can be used to realise social benefits, not only through increased productivity but also via local participation in the project. COLAS aims to maximise the use of local companies in the construction phase, and on its first project in Senegal (see below), it outsourced 30% to local companies. This included knowledge transfer to guarantee maintenance capabilities and capacities on the long term. 

“There [was an unpaved] road and we lived with the dust. We feel relieved with this new track. In the rainy season, the [unpaved] track was impassable.” – Mbaye Sarr, Chief of Boundou Village, Senegal

Example application

For the Ngoé project in Senegal, COLAS applied COLPISTE to 8 km of rural road. The project realised 40% cost savings and significant local benefits, as shown in the video below. Large portions of the earthworks and drainage works were performed by local contractors. Based on the success of the project, local authorities decided to create another new bus line to connect five other villages.

“Accessibility of transport was our concern. Thanks to this track, transport is accessible by bus and other means of transport.” – Seynabou Diop, Woman Leader of Boundou Village, Senegal