The Challenge

The project included for the construction of 22km of dual carriageway to exacting standards, this included four main junctions at Coolcour, Gurteenroe, Toonlain and Ballyvourney. From conception the scheme set out to bypass both the towns of Macroom and Ballyvourney through often very challenging terrain. In addition, the project interfaced with the existing N22 national primary route at several locations along the route which introduced challenges such as maintaining existing traffic flows.

The Solution

Following the initial design which was carried out by Barry transportation and the main JV contractor, Roadstone was contracted to construct the pavement structure. This required both the Roadstone R&D team and Contracts division to carry out extensive mix design and trials to ensure compliance with the overall pavement design. 

A brief outline of the design parameters is as follows.

The Mainline incorporates a 40-year design life

Pavement to flexible composite design

Overall Pavement Thickness Of 340mm


In order to fulfil the needs of the client the following quantities were required.

150,000-ton Clause 804/808

175,000-ton CBGM

170,000-ton Blacktop Of which recycled materials were used.

30,000-ton is Stone Mastic Asphalt of varying PSV values depending on skid resistance requirements noted within the design documents.


Prior to the construction phase commencing significant capital expenditure was deemed necessary. Potential risks to pavement durability at the interface between carriageways and lanes was identified. If water ingress was not prevented this could affect the overall design life of the pavement structure.

Therefore following this initial assessment the following plant was procured and used.

Vogele 1083–3i with extended screed purchased specifically for N22 Contract

3 no. Bomag 161AD with intelligent compaction technology

Atlas Capco – Material Transfer Vehicle

Several pieces of ancillary plant and equipment


Aside from structural integrity of the pavement, ride quality is always considered as an essential prerequisite to a successful road project. Stakeholders deem this of utmost importance as Its what the end user notices immediately. In order to achieve this objective the following measures were taken

Strict Adherence to TII And Site-Specific Specifications

Purchase of Vogele 1083–3i with extended screed of 8.5m which ensured that each carriageway could be laid in one pass

By utilizing a material transfer vehicle, sonic sensor averaging beams, and the extended screed paver an exceptional pavement surface was achieved. 

Roadstone Contracts division was able to achieve the following results. 

Average of 1.1 on binder course 

Average of 0.79 on surface course

Lessons Learned

Early-stage engagement in the design process is crucial. This will result in greater value for the client and contractors whilst maximising the use of sustainable solutions.

Recycled materials should be utilised to the upper limits permitted under current regulations. This is to ensure a reduced environmental impact from the overall project.

Early engagement by roadstone’s R&D and contracts division resulted in a greater level of collaboration between Client. Designer and Contractors. Relationships formed through this process will lead to further opportunities and continued partnerships.