The National Roads Authority (NRA) has told local councils that they should insist on a road safety audit in all planning applications for new houses opening onto national primary and secondary routes.
In a circular to all local authorities, the NRA reiterated the need for development control along main roads, and specified new requirements for road safety audits and transport assessments of developments that would generate more traffic.
The authority has confirmed that the proliferation of one-off houses along the N22 between Killarney and Farranfore in Co Kerry was one of the main reasons why it decided to replace the existing route with a new road costing €90 million.
Planning permission for many of the houses was granted as a result of councillors adopting Section 4 (now Section 140) motions in defiance of restrictions on development along national primary and secondary routes.
By permitting these houses, many of which are operating as B&Bs, the councillors ignored a long-standing rule that ribbon development should not be permitted along main roads for safety reasons and to allow for future widening.
A study commissioned by the NRA found that widening the N22 would directly impact on 140 properties and require 17 houses to be demolished. The cost of land acquisition to turn the road to a wide single carriageway would exceed €6 million.
"Development is particularly dense on the section of road between Lawlors Cross and Killarney. On this 5.5km section of roadway, there are approximately 110 residential/commercial accesses, representing 20 accesses per km or one access every 50 metres.
"A significant proportion of these accesses are for commercial properties (guesthouses and bed and breakfast properties), which generate large turning movements, particularly during peak season, when traffic volumes are greatest," the study noted.
Accident statistics for the 15km stretch of the N22 between Farranfore and Killarney indicate that approximately 15 per cent of all accidents occurred at private accesses, which would all have to be maintained as part of any realignment of the existing roadway.
This would cause "major safety concerns", the study said, adding that the potential for accidents would increase with rising traffic volumes in future years if the road was developed as a wide single carriageway with a design capacity of 13,800 vehicles a day.
"Following a preliminary assessment of the on-line route corridor, it was considered that the constraints associated with this option were such that it was less feasible than the alternative off-line route corridors and it was eliminated from further consideration." Four possible routes are still under consideration, though in every case there would be significant severance of farms.
Cllr Danny Healy-Rae, a major sponsor of Section 140 motions, said he was "not accountable for what happened over the years", before he became a councillor. A new road was "desirable", though he would have sympathy for the farms and communities it would split up.
The NRA had been invited by Kerry County Council to comment on six planning applications for houses along the N22 in an 18-month period to mid-2003. Five were "at variance with national policy" and the sixth was in an urban area.
The NRA said it had received "no response regarding the determination of those applications".
Asked why it never exercised its right to appeal to An Bord Pleanála, he said: "We're a small body and we wouldn't have the resources."