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Where will all the traffic go?

Surely the most rational of questions, from concerned community groups, retailers and elected representatives, when transport agencies propose new traffic-management measures in their area.

The Liffey Cycle Route, the north and south quays traffic-management changes, and the College Green Plaza scheme are cases in point.

In all of these situations, Dublin City Council appears to be proposing to redirect amounts of car traffic from familiar and heavily trafficked routes into, sometimes, residential areas.

So where will all the traffic go? It evaporates, right?

Actually it does. Not very scientific sounding, or even helpful, many might think. But there is a sound basis for this counter-intuitive idea, and lots of evidence to support it too.

Traffic reduction, or “traffic evaporation”, as it is increasingly referred to, is a recognised effect of traffic-management schemes. And the point of it is that, when executed well in cities with good policies, the traffic doesn’t divert onto nearby streets, it disappears or, indeed, evaporates.

This is not conjecture or wordplay. It is based on hard evidence and the experience of other cities. And there is a reason for it.

The best way to think about traffic is that it behaves more like a gas than a liquid. That’s another way of saying the more space you give it, the more space it will take. For cities to work at all, traffic needs to be managed.

Dealing with any issue requires perspective. In all of the traffic restrictions proposed by the council, the number of cars involved is very low. The M50 carries 12,000 vehicles per hour at its peak. But on the Liffey quays there are fewer than 500 cars per hour heading inbound.

Importantly, there are 120 buses per hour going inbound on the quays too. Those buses can take up to 10,000 people into the city. Therefore it is a false economy to argue for increased priority for cars.

Retail and commercial groups that do so are, in real terms, doing their members a disservice. Councillors who do so need to think seriously about the huge numbers of people living in west Dublin, who rely on the bus.

Still and all, who wants 500 extra cars passing their front door? Not many reasonable people. Most would contend that their streets have room for no extra traffic, let alone 500 new cars.

This is where the science comes in.

An important UK study, by eminent Professor Phil Goodwin and others, from 1998 and updated in 2002, shows that where such traffic-management schemes have been put in place, actually very little traffic redirects onto nearby streets.

More surprisingly, traffic levels on those adjacent streets usually stay about the same, and in many cases even reduce. The traffic really does seem to evaporate. But how can this be?

Any traffic intervention kicks off a number of processes, and the first target has got to be through-trips. No town or city should have them.

Traffic surveys by Dublin City Council suggest that more than 40 percent of car traffic on the quays is going straight through the city and out the other side.

These vehicles jam up public transport, pump fumes into people’s neighbourhoods and bring not a cent to city retailers. Long past time to get rid of them.

Of the remainder traffic, we know from surveys, both in Dublin and many cities around the world, that suburban traffic commonly has about a 40–20–40 mix.

About 40 percent of suburban households need to use their car, be it for school, business or other reasons. Typically, about 20 percent of households are using sustainable modes of transport.

That leaves about 40 percent of households who are opting to use the car. These users are the second big target. Addressing them, ironically, helps out those who need to use their car.

If you do the above math, traffic is potentially reduced by over 50 percent directly as a result of a good scheme, exactly as experienced by Professor Goodwin and his colleagues. Importantly, by doing so, the quality of public transport improves.

This is how it is possible for traffic levels in the surrounding areas to drop. The improved public transport literally sucks in car trips from these areas.

Put simply, if a new restriction is put in place, few sensible people will drive all the way to it. Most will change their journey plan before they depart.

The above might seem fanciful, but it is happening worldwide and there is lots of international evidence to suggest it is good for local areas. There is plenty of evidence from Ireland too.

One in-depth study of a temporary road closure in the Phoenix Park showed that traffic volumes across a screenline into the city centre reduced overall. It was a textbook example of traffic reduction.

North Frederick Street was once open to all traffic. Implementation of a “bus gate” in 2002 restricted cars on the same link but also, astonishingly, reduced southbound car traffic on O’Connell Street from 1,100 vehicles to 74 only.

The streets around Gardiner Square and Mountjoy Square were never saturated with diverted traffic, as local groups had feared, and public transport improved dramatically.

A similar bus gate at Parkgate Street increased car journey times into the city, but also reduced bus journey times by up to 20 minutes according to Dublin Bus.

Between 1997 and 2010, similar reallocations of road space were made on 16 quality bus corridors into Dublin city centre. In that time, bus passengers crossing the canal bridges increased 45 percent and cars crossing the canal fell by 21 percent. The average number of passengers per bus also increased.

All this serves to reduce overall traffic in the city centre and improve mobility for everyone.

It is almost comedic now to think of Frank Feely, then Dublin city and county manager, announcing the pedestrianisation of Grafton Street in 1982 as an “experiment”, which was to be reversed if proven a failure. Well the experiment seems to have been a success (although the trees he promised never arrived).

So it is disappointing, in 2017, to hear well-informed media outlets issuing portents of “traffic chaos” as a result of traffic-management measures, which are designed to improve, not worsen, the quality of the city-centre environment.

In reality “traffic chaos” is what inner city communities are living with today. The status quo serves nobody.

The current lord mayor has been particularly vocal in opposing the proposed traffic-management changes. He and other believe a solution is a boardwalk for cyclists. However well intended, such appeals are not in the local best interest.

The council estimates that the boardwalk (which is unlikely to be a success as it involves too many diversions) would cost up to €3 million. This would be far better spent on local environmental improvements.

That could transform streets like North Brunswick Street and communities like Stoneybatter, which are indeed beset, already, by traffic chaos.

We need to think differently about the potential for our urban communities. There is no reason why, with investment and good design, they cannot be fully connected, healthy and vibrant places. Arguing to protect car priority will not deliver this.

Every single person concerned about the future of the city needs to check out the beautiful website It is a compilation of before/after images from cities worldwide that have had faith in traffic management and good design.

Contrary to some views, it is a good decision to defer the Liffey Cycle Route for further analysis of a difficult problem. It is equally disappointing that the council has been forced into a climb-down on banning through-trips at O’Connell Bridge. This retrograde decision will even be detrimental to the narrow business interests who lobbied for it.

There is serious evidence that traffic-management measures, such as those proposed by the city council, not only reduce traffic levels, but dramatically improve the health and quality of environment in neighbourhoods around them.

To argue against these schemes, while entirely understandable based on rational human logic, is actually counter-productive to people’s health and well-being.

The traffic really does “evaporate”.

David O’Connor lectures at DIT and co-runs the MSc in Transport and Mobility, a new multi-disciplinary programme in transport planning. Follow him on:

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  1. David…thanx for this cogently argued defence and criticism of the various Liffey Route Cycle Options put forward. This kind of data and argument needs to get out there more, and we in Dublin Cycling Campaign will be working to do so. This cycle route needs to happen for Dublin as a model European city, and for an iconic example of where we can go as a city and as a nation.

  2. Indeed, this is why for so long the Quays have been seen as basically a dual carriageway into the city center. But it’s the same for allowing cars down every side street in the city, as currently – you allow the perception that cars can go everywhere. It all comes down to poor planning and primarily poor communication. But if you continue to allow cars parks in the dead center of a city centre, that gives another incentive (excuse) for such journeys. A congestion charge would change that pretty rapidly.
    What surprises me is that the issue of toxic car fumes has not become as big an issue here yet in the press as it has in the UK and elsewhere in Europe. A few car fume level signs on streets might change the habits of those standing at the spike or sitting on the boardwalk. Likewise in highly congested ‘towns’ such as Terenure where traffic levels are through the roof. Time for a ‘Clean’ Towns badge rather than just a Tidy Town badge perhaps….

  3. It frustrates me that Liffey Cycle process has been delayed again. Following the discussion around College Green Plaza brings even more frustration and disgust. I haven’t seen any positive developments in this subject in the City in years. Sad times.

    Very good piece, especially the study, thanks David.

    @Dave – those driving and polluting the air in the Centre live far from the smoke, why should they care? It’s us who live in City Centre that cannot man up to push this through. We need to talk to our Councillors more.

    1. Indeed. I doubt air quality is high on their agenda. It’s not just driving cars either, but I notice a lot of taxis and parked cars who sit with their engines idling, glued to their phones etc., just basically doing nothing more than spewing out car fumes into the foot paths all day.

  4. I use the bus every day, and I believe congestion is caused mainly by cars but also there could be blame to Dublin Bus too. Some simple changes to certain routes would help.

    There are so many buses that travel down the quays . I’ve noticed that people getting the 145, 37, 39, 39a, 25, 25a, 25b, 25d, 25x and 26 on the quays heading south, will alight at Ormond Quay and take a 10-15 minute walk to Nassau street and resume their bus journey from there, as its actually quicker to make that section of the journey by foot than to stay on a bus stuck on the quays!

    There is a poorly positioned bus stop on Bachelors Walk, that means all buses that stop there with the intention of then crossing O’Connell Bridge have to cross over three lanes of traffic in a very short stretch to get onto O’Connell bridge. This creates a huge bottle neck on the approach to the bridge.

    It would make sense to create a bus corridor down Dame street for these buses, crossing earlier on the quays at somewhere like Grattan Bridge.

  5. Great articles as usual Dave. My only issue is that this common sense, factual, scientific based information is not getting out there.

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