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Josef Hargrave

Global foresight manager

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Enhancing road safety by improving surface drainage

Enhancing road safety by improving surface drainage

Focus Area

Sustainability, Transport







Working in collaboration with Transport Infrastructure Ireland (TII), the project objectives were to:

  • analyse data from collisions on the road network arising from aquaplaning (hydroplaning) skid incidents;
  • using data from TII motorway maintenance and renewal contracts, identify the parameters relevant to developing a design methodology that better ensures that gradient, depth of water on the carriageway, and drainage path length allow for adequate surface drainage of the carriageway in all circumstances;
  • investigate rolling crown construction methodologies to establish best practice, and develop requirements for designers and contractors undertaking proposals for such works;
  • identify and assess amendments in the TII standards that can enhance compliance with pavement surface tolerances at rolling crowns while taking due account of other design factors such as driver comfort and reducing pavement joints in surface courses;
  • investigate amendments to pavement tolerance requirements in the TII standards to allow tighter control over construction methodologies.

Key Findings

From analyses of water depth and road gradients where collisions associated with aquaplaning were occurring on the national road network in Ireland, we developed a design methodology for road schemes that can reduce aquaplaning incidents significantly.

We also produced tighter design and construction methodologies for constrained locations where a rolling crown needs to be constructed.

The project contributed to an increase in understanding of the interaction between surface course materials, durability, road geometry, texture depth, road spray and skid resistance.

The research has led to the introduction of new design methodologies that are now widely accepted as best practice across the firm, resulting in the design of more effective surface drainage of road schemes.


Based on this work, revised design methodologies and parameters have been published in the Transport Infrastructure Ireland road geometry standards along with amendments to the TII specification for road works.

The revised standards will be deployed on all national road schemes in Ireland, and will provide road design geometries that improve surface drainage and, thereby, help to improve road safety.


Application of the knowledge generated in this project and captured in the revised TII design standards can reduce the likelihood of standing water on carriageway and, therefore, reduce the risk of accidents on the national road network in Ireland.

This research has resulted in the introduction of improved highway design and construction methodologies that have already reduced aquaplaning incidents significantly on the Irish road network.