The Transport21 road building plan is a well conceived plan for the creation of a network of trunk roads for the island, but it has several flaws and omissions. Some areas of the country will remain isolated from the trunk road network - the nearest motorway could still be more than 100 km away. And although moving between large towns and cities will be facilitated, roads in between and perpendicular to these routes will still be very poor, making cross-country journeys awkward and difficult.

Below are listed some ideas for these additions to the network. They include some strategic motorway building, which will be very modest compared with the current efforts. Most of the remainder will consist of a lot of good quality dual carriageways forming an X across the midlands, and extending into peripheral areas. There will be over 600 km of these.

In addition, a large number of schemes need redesignation to motorway to fill in gaps in the strategic route networks: the Interurbans and the Atlantic Corridor. Also some redesignations are necessary in order to maximise the value of expensively-provided infrastructure. Phase I involves roads which are ready to go, meaning they are already suitable for blue signs or will be when they open in the near future. Phase II roads will require reconstruction first or are dependent on the standard chosen for the scheme as it moves towards construction.

It is roughly envisaged that the below list could reasonably be implemented in the period 2015-2025.