High Volume Transport

Vital transport research to ensure accessible, affordable and climate friendly transport for all.

Updating Road Note 31: A Guide to the Structural Design of Bitumen-surfaced Roads in Tropical and Sub-tropical countries


The project aims to improve the design of road pavements to make roads in LICs/LMICs more affordable, more efficient, and more resilient to climate change by updating and disseminating a new online Road Note (RN) 31. The primary beneficiaries of this research will be road design practitioners, transport authorities, and research institutions in LICs/LMICs, and multi-lateral development banks, multi-lateral and bilateral donors.

Potential impact

An updated online RN 31 that will include available technologies and automate certain pavement design processes. and extend the design traffic range in ORN 31 to beyond 30 million equivalent standard axles (MESA) based on engineering evidence, other gaps such as impacts of climate change and increasingly prevalent premature pavement failures.


The project will be conducted in three phases as shown below

Phase 1

Launch meeting – TRL shall update the schedule of activities to incorporate the actual start date and any adjustments deemed necessary.
Stakeholder onboarding – This is critical for the project and TRL will assist by preparing draft ToRs for the PAG and other stakeholders as may be necessary, followed by continual engagement.
Review of ORN 31 and other Relevant Documents
Preparation of the Draft Online RN 31 and Dissemination Guide
Consultation, Workshops, and Preparation of Phase 1 Report

Phase 2

Field Investigations
Laboratory Testing
Analysis of the Field and Laboratory Data, and Data from Past Studies
Preparation of the Phase 2 Report

Phase 3

Updating of the Online RN 31 and the Guide Document
Dissemination and Training
Preparation of the Final Report
This research will create an update guide which is fit for purpose for practitioners in LICs and MICs. The creation of an online version which will contain some automated processes such as determination of alternative pavement structures for inputs of traffic and subgrade values as well as some updates.