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Not really following that diagram.

Is the top the start postion and the bottom the current position ?

Top is London. Bottom is Amsterdam.

Deloitte analysis. Pre pandemic I think.

Obviously no two cities are directly comparable but public transport provision in Amsterdam is, IMO, on a par with London so gives an indication of what we could expect if the cycling modal share in London increased substantially.

Good digging.  On "displacement" again I'd caution that we're not necessarily comparing like with like in the before and after.  I imagine (I don't know - but otherwise people are walking epic distances!) that is showing "trips" or journeys.  So it's not clear that all *distance* covered by the public transit trips are replaced by the same *distance* for cycling - which obviously has bearing on the energetics.

Even in the UK "traffic evaporation" is a thing - and when some people decide not to go a certain route by car some of those journeys simply don't take place at all.  (They could simply cease, or people find a more local alternative etc.)

In the UK currently I think you'd be right though - I seem to recall that there is data for some places (London, was it?) that journeys were shifting between public transport and cycling and walking but over the time period the private motor vehicle transport numbers (including taxis IIRC) remained fairly static.

A notable feature of the Dutch example is that they've really facilitated multi-modal longer distance transport - so bike / train / bike for example.  Excellent and reliable public transport, plus the O.V.Fiets national railway-station-based bike rental scheme is likely behind that.  However they've also retained a lot of longer car journeys.

I haven't been to Amsterdam for a while but used to go fairly often and the traffic levels felt much lower than the figures suggest.

In a similar vein if you compare rush hour gridlock and free flowing traffic the difference in vehicular numbers is not that big. Small differences in traffic volume can translate to big differences in traffic flow.

Rich_cb wrote:

... In a similar vein if you compare rush hour gridlock and free flowing traffic the difference in vehicular numbers is not that big. Small differences in traffic volume can translate to big differences in traffic flow.

Isn't this a feature of motor vehicle traffic particularly?  I'm guessing because a) unless you're just running fully occupied buses motor vehicles tend to be space-inefficient so it's pretty easy to reach capacity for few extra *people* and b) because of safety requirements we have traffic lights, which aren't required for pedestrians or cyclists as those modes can safely negociate / merge at low speeds?

Aside: lots of countries have de facto "traffic light free junctions" where safety *might* be OK e.g. when busy (that's not to say that the country as a whole has good road safety).  I recall some crazy intersections when travelling in Thailand apparently with everyone coming from every direction.  However vehicles were only going about as fast as e.g. cyclists in a Dutch city.  (Which helped because elephants don't move quickly - until they do, but you really don't want that to happen!)  Also this kind of "shared space" definitely doesn't work well (as it doesn't anywhere) for cyclists and pedestrians.

Rich_cb wrote:

If there is public transport running in the direction you want to go the marginal CO2 cost of cycling will always be higher than the marginal CO2 cost of taking the already running transport.

The problem with focusing only on the "marginal" impact when it comes to public transport is that the public transport is only running because enough people take it. Any one passenger could argue their trip only accounts for a marginal increase, but if no passengers ever took the bus/train, it wouldn't be running. 

OnYerBike wrote:

The problem with focusing only on the "marginal" impact when it comes to public transport is that the public transport is only running because enough people take it. Any one passenger could argue their trip only accounts for a marginal increase, but if no passengers ever took the bus/train, it wouldn't be running. 

Unlike planes that keep flying when empty so that the airlines don't lose their runway slots.

It's a bit of an intellectual riddle really.

If you take the aggregate carbon cost (eg cost of manufacture, maintenance etc divided by total users) you will get a completely different picture to the marginal cost.

Which is correct though?

If an empty bus is driving past my house, going exactly where I want to go the marginal carbon cost of me catching it is close to zero but if you allocated the entire carbon output of the bus journey to me as the only passenger the carbon cost would be huge.

In reality the marginal cost makes more sense for individual decisions and the aggregate cost for systemic decisions.

If that hypothetical empty bus were running regularly and I needed to make the journey regularly individually speaking it would be less carbon intensive to catch the bus than to cycle.

Systemically though it would make more sense to cancel the bus route and let me cycle instead.

According to my garmin watch last week I did 7.59 km cycle 228 calories, 7.9 km walk 706 calories. Conclusion buy a second hand car and save the planet.

I think this is why this is such a stupendously complicated way of looking at it. You'd probably burn ~100 calories during the length of that walk even if you're not moving, so you should only be looking at excess calories. In the real-world, people don't eat exactly maintenence calories anyway, so you'd have to compare excess "fuel" calories for the cyclist vs excess "surplus" calories for the driver and passengers. You have the fact that those who cycle everyday will be fitter, will process food/energy more efficiently, and therefore it's totally possible for someone who's fit, and who cycles to a desk job, to consume less food in total (have a lower "maintenence") than someone unfit who drives to the same desk job. You have to consider that some who cycle are doing so to improve their health, and so won't be consuming a "fuel" surplus (or maybe even a defecit) in order to lose weight. You have to consider that those who cycled partly for health reasons would excersise (and consume the fuel to do so) even if they didn't cycle. Finally, you have to consider that many who cycle do so for environmental reasons, and so might have a diet with a lower impact anyway.

We're better off viewing food as it's own discussion.

"From a carbon perspective you're probably better off taking certain forms of public transport than cycling. "

No.

You've mistaken energy efficiency for low carbon intensity.

A bicycle may take very few watts to power it but if the engine providing those watts is inefficient then it may still have a relatively high carbon intensity for a given distance travelled.

Here are some carbon intensities. My very rough calculation of 70g CO2 per km for a cyclist can be compared.

As user Wales56 posted earlier Cycling is 20g CO2 per km. So you're wrong.

I believe that 6 is a smaller number than 20?

Even if cycling only produced 20g CO2 per kilometre there would still be forms of public transport that are less carbon intensive.

Which was my point.

Rich_cb wrote:

I believe that 6 is a smaller number than 20?

Even if cycling only produced 20g CO2 per kilometre there would still be forms of public transport that are less carbon intensive.

Which was my point.

When I’ve got a little more time (I’m migrating servers today), I’ll have to dig into the methods used to arrive at those two numbers, because I find them highly dubious. I don’t think they’re following the same methodologies. I suspect the cycling number has considered all of the “cradle-to-the-grave” externalities of cycling, and the train one is more of a “fingers-in-the-ears” denial of all the externalities, only focusing on the energy expended to move the train. It won’t be including, building the train, building the infrastructure, maintaining the train, maintaining the infrastructure, producing spare parts, it’s probably assumed that all electricity is produced via 100% renewables and occupancy is 100%, ect.

We already know that you burn ~3 times the calories walking than cycling, so if that 20g does map accurately against the 6g of the train, we end up with ~60g for walking. So that chart is suggesting we can generate the power to move that train 1km for a tenth of the carbon intensity of putting on some shoes and going for a stroll? I seriously struggle to believe that.

Well, whatever the answer, a water powered cliff railway beats them all.

I suspect you're right regarding externalities but that brings us back to marginal Vs aggregate.

The cycling figure is pretty dubious imho.

Firstly, it appears to be based on a global average diet which doesn't remotely resemble the 'average' UK diet.

Secondly it's based on 11 calories per kilometre energy expenditure. Which is considerably below anything I've seen anywhere else.

Are you really arguing that Eurostar or a channel ferry is a form of transport that could replace a bike trip???
(Those figures look pretty dodgy to me btw.)

marmotte27 wrote:

Are you really arguing that Eurostar or a channel ferry is a form of transport that could replace a bike trip??? (Those figures look pretty dodgy to me btw.)

Exactly. Public transport and cycling actually compliment each other. It's not a battle between the two!

A bus or train is never going to be a door-to-door solution, you need something to fill that last mile gap. If you look at The Netherlands, the reason they have such huge bike parking facilities at train stations, is because people do multi-modal journeys - cycling at both ends of a train journey.

Bike + public transport will easily beat private motor vehicles when it comes to CO2 emissions (and a whole host of other metrics too). That's what the argument should be about.

I'm arguing that there are forms of public transport that have a lower carbon intensity than cycling.

Electric trains would come in closer to the Eurostar figure than the national rail figure.

Electric buses would likely be far lower than their diesel equivalents (see difference for cars).

The 20g per km figure for cycling seems implausibly low for someone eating an average UK diet (it appears to be based on a global average diet which is far less carbon intensive). 11 calories per km also seems implausibly low.

Even a slight modification of both those figures will increase the calculated carbon intensity of cycling considerably.

Rich_cb wrote:

The 20g per km figure for cycling seems implausibly low for someone eating an average UK diet (it appears to be based on a global average diet which is far less carbon intensive). 11 calories per km also seems implausibly low.

Even a slight modification of both those figures will increase the calculated carbon intensity of cycling considerably.

This is where (IMO) things get a bit complicated, because there are so many thousands of variables at play when it comes to the wild variances of peoples daily food intakes - I actually think that both of those numbers are implausibly high because they don't consider journey type/frequency.

Take this as an example:

I'm sat around in the house, I wasn't intending to do anything today, and I've just eaten a salad. I get a call from a friend asking to meet up a few km away. Now, I have a choice between cycling there or driving there. If I cycle there, then I am technically burning the energy I've consumed by eating the salad (and depending on what was in it/where it came from, that might lead you to arrive at a number like 20g/km).

However, I'd have still eaten the salad if I choose to drive (I'd have still eaten the salad if I wasn't going anywhere at all), so it's (IMO) unfair to attribute that salad as the "cost" of the cycle ride. Compared to the car, the cost of the bike journey is really 0g/km because I'm not eating anything extra, but the car is burning fuel. It's only if the cycle ride became a regular, daily part of my routine that I would change my average food intake to suit (and even then, I might not if I was using the cycle journey as a way of improving my health as well as a form of transport).

There will be plenty of cycle rides that are short and occasional and which do not incur a change in the "baseline" food intake. These journeys (providing the bike has been ridden enough to offset it's own production) are 0g/km.

You can't remove food from the equation, because that is very much a cost of the cycle ride, but the above figures (IMO) are the result of abstracting too far away from a real-world scenario. You still have to consider things like:

• People don't eat exactly maintainence - most people (according to stats) are likely in a surplus, so additional calorie intake for a bike ride may not actually be "additional".
• Occasional rides likely won't impact average food intake, so it's unfair to attribute calories burned as a cost of the bike ride.
• Some people would excersie anyway if they didn't ride.
• Some people would commute by bike specifically to improve health and would not intake extra food (at least for a few months/years).
• Fitter people use energy more efficiently and so can make bike journeys whilst still requiring less energy than someone sedentery.

I'm with rich_cb on this in that the energy has to come from somewhere.  Also while cycles are extremely efficient machines they are powered in part or whole by humans.  Humans are inefficient converters of energy into movement.  They generate a LOT of heat doing so - so much so that we need externally powered fans for our turbos to try to dissipate that!  With notable exceptions covered on this site they are pretty feeble motors - their maximum power output is tiny compared to a car and over anything more than a minute it drops considerably.

Further - the energy (and wider environmental) cost of our food - especially in Western nations - is huge.

However - humans will move a certain amount regardless.  (To keep healthy we need to as has been mentioned).  With the aid of an extremely efficient machine to convert our normal efforts into forward motion (cycle) this can fit into our lives very well for a moderate amount of extra calories.

One aspect not mentioned before cycling as a "life enhancer".  It is foolish to look at our current travel patterns and simply compare replacing all car journeys with cycled ones.  Aside from being physically unrealistic cycles lend themselves to different patterns of travel and indeed life.  More local.  Which enhances communities.  Ultimately the real potential for cycling to improve not just "carbon emissions" but our wellbeing is by aiding us to travel less but get more benefit from it.  (Sitting in a car in traffic is a real waste of human potential)

So mass cycling is more "superpowered walking".  Recall that cycling started as a replacement for the horse.  As opposed to cars which were a new type of carriage and are also (now) a competitor to the train.

chrisonatrike wrote:

I'm with rich_cb on this in that the energy has to come from somewhere.  Also while cycles are extremely efficient machines they are powered in part or whole by humans.  Humans are inefficient converters of energy into movement...

Further - the energy (and wider environmental) cost of our food - especially in Western nations - is huge.

100% agree, and I think what we're actually having here is a discussion about the impact of our food chain, and how our food choices are factor into this (veganism vs animal agriculture, food miles, ect). Except, it's being weirdly framed as a discussion on cycing.

If we are going to do the exercise properly though I think you have to go a lot deeper into the true energy costs of car ownership, so much like you can look at the fuel cost of a journey and ignore the overhead of running a car, which I have a sense our economics professor is doing, if you look at the carbon cost per mile of a car, electric or ICE, then you have to factor in the build costs and arguably the costs of the infrastructure.

That last one is a Lulu. Consider the road infrastructure of the 1960s. What is the carbon footprint of that expansion of the road network simply for capacity and the carbon footprint of the ever-increasing added infrastructure that is added purely to control careless and dangerous drivers.

We can accept that basic level of infrastructure is required, even for a world of optimal public transport and walking and cycling but surely we are at a stage where there is a massive hidden cost, e.g. in roads and driveways simply to store the excessive number of cars that exist.

henryb wrote:

And yet still no cycling kit manufacturer makes cycling tops with a pocket you can fit 1kg of beef in!

No need.  You just stop at a field of cows and take a bite.

Neither, cowboy; or rather both.  You're right about the bullocks though although they come with their own emission issues:

I thought he was making a satirical comment highlighting the massive role of farming and eating habits in climate change and environmental destruction... then he had a pop at the vegans?