It's not so long ago that driving from Belfast to Dublin took three hours at best, and frequently much longer, as traffic crawled through Newry, Dundalk, Drogheda, Balbriggan and the northern suburbs. Today the entire journey - city centre to city centre - can be safely completed in well under two hours, mainly thanks to the motorway construction south of the border, although significant improvements to the northern part of the route have helped accelerate the journey time.
But why have there not been comparable improvements to the key routes in Northern Ireland?
Elsewhere in the Republic motorway upgrading of the key arterial routes to the major cities of Cork, Limerick, Galway and beyond has similarly slashed journey times and provided a tangible boost to the economy, regional prosperity and social connectivity.
Substantial European subsidy, shrewdly accessed by the Irish Government, has been an element in financing some of this critical infrastructure development.
But the truly clinching factor, during a period of unprecedented economic stress, has been the introduction of tolls on the main roads.
As regular Belfast-Dublin travellers now well know, one has to pay a €1.90 toll each way to traverse the route, with higher charges applying to other classes of vehicle.
There are similar pay-as-you-pass toll booths on about 300 kilometres of other motorway routes, but by far the busiest route is the M50 C-ring around Dublin, which is used by about 100,000 vehicles a day, generating revenue of about €275,000, or well over €100m a year.
One has only to observe the many retail and commercial developments that have taken place alongside the M50 to see how providing top-class roads at this and other strategic points, such as the Dublin Port Tunnel, produces direct benefits to the national economy.
In all Ireland has 11 toll roads, with 10 of them having conventional toll booths - some of the channels automated, some with a cashier.
If your car has an electronic tag it is possible to drive straight through. The other option is to pay cash at the booth.
The M50 is a barrier-free toll, which relies on automatic number plate recognition. Regular users can buy a multi-journey pass, or, alternatively, drivers can pay the toll at a number of convenience stores and other places before 8pm the next day.
Those who fail to do so receive notification of a fine at their home address. For a time Northern Ireland offenders were not pursued, but they are now.
The substantial cash flow the tolls create is used to defray the cost of building the motorway network and to pay for its upgrade and maintenance.
Nine private companies operate the tolling system in Ireland in partnership with the Government. In return for putting up a substantial part of the original construction cost, they earn their investment back under agreements that can last as long as 30 years.
It has to be said that these private-public partnerships do not always conform to expectations. The actual traffic flow on some of the routes has failed to fulfil the forecasts, causing disputes and demands for terms to be radically revised, but there has also been an outcry about the significantly lucrative returns being earned from the busiest routes.
There was a time when roads in the north were far superior to those in the south, but, despite substantially increased traffic flows, the standard and quality of our roads has steadily declined by comparison.
But while the Stormont administration has drawn up grandiose schemes to modernise the crumbling under capacity of our roads network, the austerity of the times has dictated that these schemes have either had to be shelved or scaled back time and time again because of the lack of funds.
Stormont recently gave the green light for a £165m plan to build a major interchange at York Street linking three motorway junctions, accelerating journey times for 100,000 vehicles a day through Belfast and for vital services to the city port. But, with Brexit looming, the promise of some vital 40% EU funding for the scheme is now in serious jeopardy.
Other strategic developments which have been seriously compromised by lack of funding are the upgrading of the A5 from the border at Aughnacloy to the north west, and the A6, the key route linking Londonderry and Belfast.
Much preparatory construction work on the A5 took place some years ago, but the financial crash in the Republic caused Dublin to withdraw the offer of a substantial cash contribution based on improving access to Donegal. With the collapse of the financial framework, the project was indefinitely delayed.
The A6 improvement has also been delayed by lack of funds, although part of the scheme to bypass Dungiven is set to get under way soon. The pace of updating the rest of the route can't even be calculated, because of enduring uncertainty about the funding available in the years ahead.
A collateral effect of the delays will be that the ultimate cost of the schemes will be even greater than the current estimates.
It's not always lack of money that holds the road builders up. We've had tree-huggers and utopian idealists forcing planning to a halt by insisting on habitat and environmental studies.
More recently protesters challenged the A6 artery, because it would destroy the Sperrins landscape that had inspired the poet Seamus Heaney. His family were quick to disassociate themselves from this proposition.
There is, though, widespread consensus and an economic imperative that our creaking traffic structure must be promptly upgraded. Why, then, has the Executive not even considered the case for tolling?
Many countries have long had tolling systems, which are widely accepted as an effective way to fund the high-quality road links a modern economy depends upon.
There's nothing novel about the practice, not even in Ireland, where in the 18th century we had turnpike roads, so called because there was a gate across the road, opened on payment of a toll. At one stage, before the advent of the railways, there were 1,500 miles of turnpike roads.
In modern times in the UK tolls have financed several key infrastructure developments, including the Severn road bridge linking England and Wales and the M6 relief road in the English Midlands near Birmingham. There are no valid reasons, then, why the Executive and Assembly should not bring forward tolling schemes to finance the sorely needed improvements to the York Street interchange, the upgrading of the A5 and A6 as well as the Narrow Water bridge linking Down and Louth, another key project eligible for EU assistance that would boost tourism on both sides of the crossing.
Apart from the long-term economic gains of these schemes, the hard-pressed construction industry would immediately benefit from investment creating badly needed jobs.
But how the administration finances these schemes will require careful consideration. Many public-private partnerships have been carelessly prepared, causing crippling repayment problems for many schools, hospitals and other public facilities, while the private beneficiaries have long since earned back their original stake.
There is a notorious example here where the providers of additional hospital car parking are set to earn lucrative dividends for years to come out of all proportion to their original stake.
Public-private schemes are not necessarily a bad thing, but they need to be far more rigorously structured in favour of the taxpayer. But another way to raise the cash would be for the Executive to borrow the money at the current historic lows in interest rates and use the toll income to repay it.
The Executive and Assembly need to focus on the prompt delivery of these vital schemes, rather than perpetually postponing them. Tolling might well be the answer.