A UK Case Study:
During the initial design stage of a 1.6 km link-road for the UK's Major Road Network, AECOM hired ORIS to optimise pavement design, taking into account environmental impact and maintenance needs. Using ORIS’s digital project impact assessment capabilities, our client was able to assess different design options to find the optimal solution between cost reduction, carbon impact mitigation and limited natural resources consumption. A particular emphasis was made on anticipating maintenance needs to evaluate the long term costs - over 60 years.
Project overview & methodology
Using ORIS on a 1.6 km link-road for the UK Major Road Network, different design options were considered including fully flexible pavement options compliant with DMRB standards, including Thin Surface Course System (TSCS), Hot Rolled Asphalt (HRA), and Flexible pavement (TSCS) on a Hydraulically Bound Mixture (HBM category B) layer. Rigid pavements were discarded due to low traffic volume and initial cost comparison.
AECOM used the Whole Life Costing and Key Performance Indicators generated by the ORIS platform analysis to select the preferred pavement design. The analysis included producing a maintenance life cycle plan and calculating the Net Present Service Value. Maintenance activities involved crack sealing and surface dressing, and overlays were discarded. Design lives of 12-40 years were considered for the pavement designs.
What were the key levers of improvement?
- Local materials: The sourcing of local construction materials was prioritised
- Circular economy: a by-product (steel slag) derived from the steel industry available locally were used in the surfacing of the permitted pavement designs to replace 50% of the aggregates, further reducing the consumption of natural resources while maintaining the performance standards.
Pavement construction cost
The fully flexible TSCS design was the most cost-effective option in terms of direct construction cost (£1.75 million), providing a significant reduction of 7% compared to the flexible on HBM-B design (£1.88 million), and a reduction of 5.4% when compared to the fully flexible HRA design (£1.85 million).
Whole Life Cost (WLC)
The WLC appraisal factored in the maintenance activities required by the design options and the periods of time in which it will be required. Based on the Net Present Service Value, the Fully Flexible TSCS proved to be the most economically beneficial design, with a NPSV of £ 3.23 million, followed by the flexible HBM-B on design, with a NPSV of £ 3.23 million (4% higher). The fully flexible HRA was the less economically beneficial option (NPSV of £ 3.42 million), despite the higher residual value at the end of the 60-year analysis period resulting from the replacement of surface and binder layers in year 60.
Over the required 60-year analysis period, the fully flexible TSCS generated the lowest material consumption ie. 83,400 tonnes. The flexible HBM-B design consumed about 86,600 tonnes, yielding the highest consumption due to the materials required for replacing the HBM-B layer over the 60-year analysis period. However, 50% of the aggregates used on the surface layer of the above mentioned designs were replaced by locally available steel slag, saving a total of 3.9 tonnes of natural resources.
Whole Life Carbon
In terms of environmental sustainability, the fully flexible TSCS emerged as the most favourable pavement design option, emitting a total of 2,810,000 eq. kgCO2 equivalent over the analysis period. The carbon emissions of the fully flexible HRA and flexible on HBM- B design options were 10% and 11% higher, with 3,090,000 and 3,120,000 eq. kgCO2 equivalent emitted, respectively. In addition, approximately 58% of the carbon emissions were attributed to the maintenance activities, which emphasises the importance of evaluating the entire life cycle of an infrastructure project.
Empowering our client to deliver the optimal sustainable infrastructure design
ORIS is a powerful tool that enables sustainable and efficient infrastructure development. As the first construction materials intelligence platform for low impact infrastructure, ORIS offers innovative impact assessment capabilities that can be tailored to the unique needs of each project. By leveraging data-driven insights and multiple criteria analysis, ORIS helps decision-makers identify the most cost-effective, environmentally friendly, and long-term maintenance solutions. This project is a perfect example of how ORIS can be used to achieve sustainable infrastructure development, promote circular economy, and reduce the environmental impact of construction projects.