The Government is right not to have rushed into a decision on whether to proceed with a completely over ground Luas or to place it underground in the city. To have taken a decision of such long-term importance to our capital city before the Government had even had a chance to read and study the 200page Atkins report would have been grossly irresponsible.

This report confirms my long-held belief that the light-rail traffic to be carried would greatly exceed the forecasts on which the original decision to go overground was based. Those forecasts have been out of date for years. For example, the report states that even after revising upwards the original 1996 estimate of car ownership in the Dublin region, CIE's forecast E for 2006 underestimated likely car ownership by almost 30 per cent.

CIE's proposal to handle this volume of traffic with 30-metre long vehicles to carry 200 passengers was never realistic. After my initial discussions with them in 1995/96, they opted for 40-metre vehicles - a decision confirmed by the Atkins report. But this report goes on to say that even these vehicles may be inadequate within 15 years.

In this connection the report says the maximum tolerable frequency is 2.5 minutes in each direction - so on average traffic on all cross-streets will have to be blocked very 75 seconds. And at O'Connell Bridge the need for two-minute traffic light cycles will, the report says, involve "queueing and bunching" of vehicles when slots are missed, with vehicles being "stored" in Dawson Street and Middle Abbey Street. This frequency limitation means that for future traffic, huge 50-metre vehicles (half the length of Croke Park) will be needed. Because of their length these will be unable to wait on O'Connell Bridge, so that both quays will have to be blocked simultaneously as each vehicle passes. Many other design changes will also be needed.

This report shows that the surface alternative will cause disruption in the city centre and deterioration of the environment for over two years, affecting each section of the route for four to six months, with closure of narrow streets. By contrast, the underground option would affect only the underground station sites at O'Connell Street and Trinity, where the effect would be minimised by temporary road decks.

Whereas the surface option will increase average queuing time for cars and goods vehicles, the underground option will reduce queuing time, increase average speeds in the whole area inside the M50, and mean less constrained modifications to city traffic management. The report adds that, "the best environmental option is therefore the underground option with additional traffic management in the inner city". As I pointed out 18 months ago, the underground option offers faster times from the suburbs to the city centre - cutting the Dundrumcity time by almost a fifth and the Tallaght-city time by well over two-fifths. As a higher capacity system it also offers a higher level of travel comfort, due to the higher potential seat availability. It also offers potentially greater scope to serve key points of traffic attraction and interchange. On accessibility, fewer stops on the underground system (25 as against 33 between Dundrum and Tallaght) is a negative point, offset by the fact that "the underground option provides a generally high level of accessibility, particularly for the car available market".

And, so long as public transport is given priority, the underground option avoids constraints imposed on buses by the conflicting demands of LRT vehicles on city centre roads. Finally, the underground option has clear advantages in terms of reducing conflict between LRT and road traffic and pedestrians in the city centre, and the associated risk of accidents.

In the light of these very many arguments in favour of the underground option, the question arises - why does the Atkins report nevertheless recommend the surface option?

The only reason given in the executive summary is that the underground option will cost almost twice as much as the surface option, and further extensions to it would also cost more - and that there is more certainty and less risk attached to the surface option.

As against that, the next paragraph of this summary goes on to say that the underground option will not only "be able to carry more people in greater comfort than the surface scheme" but that because of the benefits it brings to road users, the underground will almost certainly provide a better rate of return in terms of the wider social costs and benefits - though both options are viable in economic terms. Finally, `the underground option has the better economic case" - yielding an additional £150 million of benefits over 30 years.

Despite all this the report prefers the surface option, apparently so as to husband scarce resources and because of what seem to be a fear that if extra money is spent on the better underground option, this might be at the expense of funds for other aspects of the Dublin traffic strategy.

Frankly, that seems a very weak basis for taking a decision which the report itself sees as less economic in the long run - and which on very many practical grounds is shown to be less desirable. I hope the Government will next week have the courage of what seems to be this report's underlying convictions. It should reject the report's timorous recommendation.

It has to be said that this limited LUAS proposal under consideration - whether overground or underground in the city centre - could by itself solve Dublin's traffic problem. A much more extensive LRT system could make a significant contribution, however. If the initial Tallaght-city centre-Dundrum route is extended, as originally proposed, to Cabinteely; if the proposed additional route to Ballymun is built; and if a further route were to be built via Broadstone and the old rail track to Liffey junction and onwards to Finglas, and perhaps also Blanchardstown/Mulhuddard - then such a network, in conjunction with the DART system, would provide rapid transit facilities for a substantial proportion of Dublin commuters - especially if supplemented by feeder buses from outlying parts of the suburbs through which it ran.

For this to work effectively, however, the Luas and DART networks would have to be connected by a a link between Luas O'Connell Street and Connolly DART - a link that in time could be profitably extended to the East Wall area as it is developed for housing.

A network on this scale will certainly be needed to compensate for the city centre congestion brought about by overground Luas - which, it should be recalled, will exclude all cars from the key Dawson Street College Green section while also reducing Dawson Street to a single bus traffic lane, as well as interrupting at intervals averaging 75 seconds all east-west streets from the Grand Canal to O'Connell Street and all north-south streets from O'Connell Street to Heuston to Inchicore.

Naturally, such an enlarged network must be complemented by bus lanes on roads into the city that run between and parallel to the Luas and DART routes - and these bus lanes should be introduced, and enforced, without further delay. It is ridiculous that this facility, promised years ago, has not yet materialised on any significant scale.

Car-owners will continue to congest the routes into and out of our capital until they are faced with paying the full cost of the space they are using, as they use it. Dublin's bridges over the double circle of rivers and canals provide ideal points for the necessary electronic charging mechanisms.

Until we use road pricing to reduce car traffic to a level that allows the efficient operation of buses, no amount of expenditure on buses will provide an efficient service.

It is time that we faced this reality.