Debunking the Induced demand argument

You might as well try to debunk gravity.

Your first point: your new motorway won't get clogged because you grossly overprovisioned, but I guarantee you that if you counted the traffic along the corridor before it opened, and then again a couple of years later, you'd find it massively increased from a small base. Where did those extra trips come from?

Induced demand exists. Every time you improve a link, it brings in people who would not have used it previously; it also encourages people to use the link more often. This is sometimes the desired outcome - road improvements to tourist areas and retail zones are done for this exact reason.

If you widen a commuter road, people living further away will consider commuting into that city because capacity has increased, and the wages are usually higher in city locations. Other commuters may be tempted to switch from using the bus, to instead using a car. Cyclists may choose to switch to a car now that traffic has "improved". But that means that before long the road is back to its earlier, congested, level of traffic.

You are free to deny this, but just be aware that you're not denying some "green ideology", Induced Demand is an observed fact of traffic planning that's been seen everywhere on Earth for over half a century. When the huge commuter road networks were built out in the USA in the 1950s and 1960s, induced demand was factored into the projections, but the planners back then didn't realise that it's not a once-off spike in demand, but a continuous growth in traffic.

It has happened in Dublin. The M50 freeflow scheme caused traffic numbers to increase on the mainline, as drivers switched to cars. The new road induced demand for road travel. Same thing happened after N7 was widened, same after Newlands Cross. Every time you make a road easier to use, it gets more users until it clogs up again. That's the phenomenon you're trying to say does not exist.

I understand why people might want to debunk "induced demand" but bear in mind that it's not a bad thing in and of itself. Often you actually want to use the road building to stimulate the growth. It's actually one good way that a government can influence economic growth.

Induced demand is only really "bad" when it's lopsided and skewed towards one unsustainable mode. That is to say when you don't invest in sustainable modes at all and only really invest in roads. Unfortunately that's been us for the last few decades. Likely because roads are great "bigger CapEx/smaller OpEx projects" as compared with, say, rail. Also likely because of our very dispersed historical settlement patterns.

So the counter-argument to people highlighting "induced demand" shouldn't really be "that's a myth", rather it should be "we're investing heavily in the sustainable modes on the same corridor, and the induced demand isn't a bad thing". The catch is that you need to keep measuring your sustainable mode shares and trying to improve them, and local authorities are loathe to be bound by this (because it's quite difficult to improve mode shares, because cars are a sunk cost).

I assume you've seen this...

That's a seems to be a long way of saying you don't believe in induced demand. Despite the overwhelming evidence.

I don't disagree there are issues with public transport. On my own train route as more people used it they made the trains smaller instantly causing overcrowding. Very unpleasant. Partly the reason I didn't renew my annual rail ticket and switched back to the car pre COVID. Post COVID the traffic on the train isn't quite recovered and that's partly why I'm back on the train some of the time.

No point in this unless there are buses to get on. At present, the bus service cannot even run all of its existing timetable.

However, there needs to be a willingness to run buses which won't always be revenue raising. One example would be express buses on the M50, which should have been there from the day the road opened. A road was opened which greatly improved driving times but no attempt was made to ensure that public transport remained competitive to that. Perhaps there was not the capital to invest in the M50 and a metro or the like but there surely was enough to run a bus.

Through my old estate they widen the road chopped trees to great a bus lane. Cost a fortune.

Then artificially bottlenecked it two places to a single lane for no reason.

They also put in a set of lights that were not needed.

I think the case is somewhat overstated. And in the case of Dublin, it only stands to reason that there would be less peak time private car use if there had been a functional public transport system and/or a decent supply of affordable accommodation.

I disagree. If you look throughout Europe and their cities you will find in many cases that not only did their governments go much further to prioritise people's ability to get around by car than anything we ever did, but they also provided and expanded upon world class public transport systems. This is common in the UK for example where city centre motorway networks are often accompanied by full scale regional metro systems, but also in cities like Amsterdam where presumably significant money was spent on things like the IJ-tunnel and the A10 ring motorway (which fully encircles the city), while they maintained their extensive tram system, while building and continuing to improve their Metro at the same or similar times.

Blaming "society and culture" or "induced demand" for the failure of successive governments to invest appropriately in ALL forms of transport (and the predictable problems that caused) seems to me to be a case that is at best overwrought. And the housing mess certainly isn't helping.

Though, to be fair, we did vote for these clowns so "we the people" must take some responsibility.

London has many of the same problems as Dublin, growing continuously with housing and transport not keeping pace, as your link shows. They are trying, Crossrail has no doubt helped, but they'll need to continue and pick up the pace if the population growth of London is to continue. I had been thinking more of Northern cities in the UK in my previous posts.

Manchester also has a weird tram-metro hybrid thing and Liverpool has a regional electric railway system. Newcastle-Upon-Tyne is the example I'm most familiar with and they simply do not have the same problems as Dublin has. Nowhere near.

I find it interesting that London has been mentioned in this thread because it as far as I am concerned actually debunks the induced demand argument. The claim - if I understand it correctly - is that if you provide more things for drivers, more people will drive, making traffic congestion ultimately worse - and that this is the only cause of traffic congestion, not for example a lack of housing or public transport, the same being side issues at most. Yet, London not only has not built new roads for decades, but has actively sought to discourage people from driving. They have Congestion Charging, an Ultra Low Emissions Zone and a lot of punitive 20MPH limits citywide. And these rules get more onerous on an ongoing basis. Yet congestion (at least according to the poster above) seems to keep getting worse.

How is it possible that a city that seeks to actively discourage driving (i.e. the opposite of inducing demand) keeps having more and more congestion?

By any chance was that research done in a city or country where payment and ticket checking is done in a frictionless or low-friction way? The actual process of getting 70+ people onto a double-decker bus when every one of them has to interact with the driver is extremely slow, and that in itself is a huge disincentive to use the bus. Pre-Covid, the 215 bus here in Cork regularly took 15+ mins to board at the stop by the City Gate business park (it may still do but I now WFH). That 15+ mins is very inefficient use of a valuable asset and very wasteful use of the driver’s salary. In Berlin, the system is trust-based and your ticket is in a smartphone app. You just get on the bus. There is no validation or interaction with the driver. If the PT operators can’t get with the year 2022 and embrace a system like this, then they shouldn’t be allowed charge at all. The friction is part of the problem.

By the way, I realise that €262M is a lot of money. But it has to be seen it the context of the potential economic benefit of a massive mode shift to PT and commuters having a bit more money in their pockets for elective spending.

@SeanW Don't try frame me, please. What I said there does not fit your summary of it. I'm happy to say I am very much in favour of road construction... we have a lot to catch up on in this country. That doesn't mean I'm blind to what happens when you try to apply road-building to transport problems that have much better solutions,though.

Once you go beyond two lanes each way with limited access, you're in the land of diminishing returns in roads... and if you're getting traffic jams on wide roads at morning and evening commutes, then adding capacity to that road will never get you out of that hole, because the problem is one of throughput, and private car travel has lousy throughput.. encouraging more of it will just set you up for the same problem again in a couple of years (and yes, I did consider other factors when I cited N7 and M50.. all that those other factors did was accelerate the return of congestion: they did not create it).

With an average 1.2 people per car, and each car needing eight to ten lane-metres of road, cars are basically the worst possible way of getting lots of people in and out of a place.

So, my position is we should build more roads, but for connectivity and safety, not commuting: commuting is best done on public transportation. Induced demand works both ways: make public transport reliable and convenient and people won't feel they need to drive everywhere; keep spending the transport budget on adding road lanes, and they will.

This is simplistic. It depends on where the use is. Plenty of roads throughout the country were improved 50 years ago and perform their job to this day. The motorways will do their job except perhaps for the 30km around Dublin and perhaps Cork.

And while what you is true of cities, LA has less road capacity than most US cities.

The problem with public transport is that people are expected to suit the transport, rather than the transport serving the people.

I used to live in Munich a long time ago, and yes, it is an example of how things should be done, but it has many advantages that Dublin doesn't have in terms of building out public transport: it's flat, it has very little suburban sprawl, and the surrounding towns are very compact with high density housing. Munich also had a very tunnel-friendly geology, and the dubious "advantage" of being part flattened in WW2, allowing a lot of the U-bahn to be built as cut-and-cover.

And Munich might be officially only the size of Dublin (1.5 million vs 1.2), but its hinterland has over 5 million inhabitants. It is also has a strong local government with real powers, as well as being the state capital of Bavaria, Germany's wealthiest state, so works in Munich have three budgets to dip into: the Federal transport budget, the Bavarian State one, and its own city budget.

The big success of Munich's transport (and German transport generally) isn't so much the infrastructure as the simple, unified ticketing: your S-Bahn, U-Bahn, Tram and Bus travel has all been usable with the same ticket for about fifty years, even though these are operated by different companies (the City of Munich owns the trams and the Underground; Deutsche Bahn owns the S-bahn commuter railway, and the city and various private companies run the buses).

With Leap, we now have the same idea here, but we still don't have the simple pricing system they use in cities like Munich, where a ticket is for any journey on any means within a period of time.

But no public transport is perfect, and Munich still has holes: there is a bizarre desert of transportation around Perlach in the south-east, and the geography of Munich itself means the U-bahn hugs the Isar valley and doesn't stretch very far to the east or west. But the long term vision is what we should be aiming for with Dublin (Munich's first U-bahn line only opened in 1971, and it was just 13 stops along what is now U6... over the decades it has steadily grown to nearly 100 stations).

This was all done as a reaction to horrible car traffic in the late 1950s and early 1960s. Munich could have widened its streets (and it did do this where blocks were flattened by bombing), but extensive road widening would have cost even more of the city's buildings, and there just wasn't the apetite for it, so the city looked for an alternative to just making more room for cars, and that was to build a real alternative to roads for mass transport.

But one thing you also notice about Munich is there's a different attitude to public transport, which you really see when it comes to buses. When I worked in Munich, I would occasionally see the head of my company (a branch of a multinational, employing 200+ people) on the same bus as me. I cannot imagine an Irish executive doing the same, and until that prejudice against bus transport changes, we won't make the kind of progress that other countries can.

Lord save us from economical public transport.

I'd imagine the tens of thousands of people who use the Luas every day are saying WTF to you right now.