If you are a car commuter in Dublin, do you ever look upwards at the traffic helicopter and wonder whether we all could fly to work? If only that third dimension in our urban space, height, were available!
Traffic could spread out, at different bands, as in the recent movie The Fifth Element, where 23rd-century New York commuter vehicles (in simulation, of course) float at high speed through skyscraper canyons.
Alas, in our real world there are few examples of commuting by air, the main prohibitors being cost, safety and air traffic control considerations.
There is, however, nothing new about three-dimensional street architecture. In the 1950s, during a burst of urban renewal, planners saw possibilities for multilayer street design.
Pedestrians could be on level one, strolling about in a system of foliaged weather-protected shopping malls. Delivery vans and light passenger vehicle movements could be on the first level down, public transport at the next level, cars beneath that, heavy goods vehicles beneath that, and so on.
This philosophy even spilled over into CIE's now-abandoned plans for a Dublin transportation centre in the Ormond Quay/Temple Bar area. It also underlies the debate about whether Luas should be underground or at street level.
In Sydney they went one step up and put the Darlington Harbour transit system above street level. Nobody has yet suggested putting Dublin's public transport system up on stilts.
It probably would not be technologically possible, except for the raised track sections at Ranelagh and Milltown on the old Dundrum line, and would be - if the Sydney experience is anything to go by - environmentally unacceptable.
So the debate is about putting our public transport system, or at least part of it, underground. This highlights our urgent need for a third dimension in urban space.
Dublin's street system is practically full. Gridlock, which is a traffic condition where the volume of vehicles occupying a given street system makes it physically impossible for any of them to move, is occurring with increased frequency.
Why are our traffic problems worsening? For a start, general affluence is generating more car movements. Additionally, our reward system is encouraging a shift to larger cars. Car sharing and car pooling levels are low.
A crazy parking policy means that those in the city all day long (commuters) grab the best spaces early in the morning, while those coming into the city later (the customers) must drive around competing for the remaining spaces.
The traffic count rises as vehicles circle in "hold" patterns. Some drivers adopt guerrilla tactics, involving elaborate hovering.
Where parked cars impede shop access, van drivers must unload from the innermost traffic lane rather than the kerb, even if traffic behind must wait. Problems build upon problems, until eventually traffic flow becomes slow, unstable and unpredictable.
Exceptional events - such as road works, accidents, bad weather - lead to chaos.
Can anything be done? The Dublin Transportation Office certainly is trying. Operation Freeflow has the right idea - try and keep the arteries free.
This can be achieved by tougher parking rules, and by getting more people to use public transport. The key question is whether it is enough.
Is public transport attractive enough, and will sufficient publicminded people go for this option with the heroic goal of freeing up enough road space for the rest of us?
It may be that more fundamental steps will be needed. Tougher parking rules hurt, and create irritated voters. They are, in any event, inherently inequitable.
Five or even 15 parking tickets on a 98 D Mercedes may mean nothing compared to just one ticket on a nine-year-old Toyota. Long-stay parking in the city centre, which is mainly the prerogative of the office worker, should be banned.
Instead of favouring car wastage, tax incentives should encourage employers to give public transport vouchers and organise car pools.
Short-stay parking off-street should be free. A licence supplement should be required to bring a one-occupant car into the inner city area during the peak period.
Are these suggestions just "pie in the sky"? What do other cities do?
Singapore has had a much-publicised area licensing system for many years, under which access to the central city is restricted during commuting hours and subject to a daily supplementary licence. At present, the scheme is being extended to involve electronic tolling and smartcards.
Cities such as Athens and Paris have experimented with alternate-day banning of cars with odd and even registration numbers. There have been many successful car pooling schemes in America, particular where employers take a lead and traffic priority (such as permission to use bus lanes) is given to high-occupancy vehicles.
A sophisticated car-sharing scheme is growing across Europe. This involves breaking the strong connection between car ownership and car usage, with drivers drawing from a communal car fleet on a pay-as-you-drive basis.
And what about Luas? The jury is still out, so to speak, and in the balance are questions of the real environmental impact, allowing for disruption during track laying and/or tunnelling. Also of interest are the numbers of former car drivers which LRT (light rapid transit) systems attract, as opposed to former car and bus passengers.
This is a key statistic, if the object of the exercise is to get cars off the roads.
And what of tunnels? A West-East tunnel under the Liffey would alleviate traffic along the quays greatly, and is especially attractive if the private sector is prepared to provide it at no cost to the public.
Tolling technology has improved enormously, to make a realistic pricing approach practical. The question of tunnels for Luas is a matter mainly of cost and environment, given Dublin's narrow streets and the sheer impossibility of fitting a rail system on some of them.
The possibility of a freight tunnel under the Phoenix Park, to connect the port invisibly to the Islandbridge area, seems eminently sensible given the tunnel already exists.
These options highlight one of the great conundrums in planning urban infrastructure today.
Environmental sensitivities mean that the planning process is slow. The costs are enormous, meaning that errors are expensive. The life of the investment must be long, to recoup the cost in money or in less tangible benefits.
A city becomes "locked in" by its pattern of transport infrastructure and so must be really sure of its long-term requirements before proceeding. And it is very difficult for anybody to be sure of long-term commuting needs.
It is here that one has the curious feeling that in the rush to spend structural fund money on transport infrastructure, Dublin may be overlooking some of the more futuristic options which are now rapidly becoming available to solve commuting problems.
Conventional transport solutions are based on conventional notions of commerce and human interaction. There is an implicit presumption that workers must be in adjacent office blocks at common work times, and that face-to-face interaction is essential for business transactions.
Recent advances in information communications technology have turned these assumptions on their heads and raise possibilities for more flexible forms of commuting and, especially, partial, or part-time, telecommuting.
It now seems that electronic commuting may offer real possibilities for the development of a fourth dimension in urban space - based on time.
Each office worker in Dublin could, for instance, spend a part of the working week (e.g. a day or a half-day) at home, in rotation. Work concepts could be redefined and redesigned to allow some tasks to be performed outside the office and at more convenient times.
There has been some concern about the social implications of home-based work. These have been based mainly on the extremes of always working from home or always being office-based.
There are now many in-between options, and Ireland's new young workforce is open to new ideas - especially those which may eliminate today's massive commuting time waste.
Looked at in very simple terms, were every Dublin commuter to work from home one day each week, in rotation, commuter demand would be scaled down by a fifth. Because traffic effects are non-linear, that fifth could be crucial in reducing congestion levels significantly.
A 1985 study by the Southern California Association of Governments found that a 32 per cent reduction in freeway congestion could be achieved by just 12 per cent of the workforce telecommuting.
It looks as if the gridlock scenario will be with us for some time. Whichever of the proposed infrastructure solutions are adopted will take time to implement.
The construction process will itself add to congestion. Meanwhile some of us will work from home, just some of the time, on tasks which are relatively time and location-independent.
In the absence of policy, commuters will find a range of "default" solutions. With a definite policy, so much more would be possible.
We should think hard about the strategies appropriate to the commuting needs of the next century. On the way, we might find surprising solutions to today's problems.
James Crowley is professor of transport policy and logistics at UCD
Tomorrow: Tom Coffey, chief executive of the City Centre Business Association
