This topic is about the cost of transport and incorporating the comparison of greenness. This will be a long and evolving note. It was prompted by a friend who said that it was a myth that travelling by train was more eco friendly than by car. I am treating this a solely a means of doing comparison based upon certain metrics.  For example cost, fuel consumed, CO2 emitted, time taken and so on. I do not propose which is the most important metric that should be considered. The answer depends on who (individual, collective, or administration) is making the decision, by what metrics, and what the starting point is. See here for a discussion on decision making.

I assert that an individual will make (complex or simple) choices about their mode of transport  based upon their preferences rather than those of a larger entity such as an administrative government. Personally as an individual I am far more interested in economic measures rather than greenness measures. I am interested in  the effect on my disposable income. Others may well make personal decisions based on different criteria. To that end it is my opinion that we as a country should become more self sufficient in fuel and import less. This mayl make the country econmonically healther and myself along with it. I do believe that persuing strategies which improve the economic situation can reduce the impact on the environment.

Before digressing lets have a look at some examples to get a benchmark view. To understand some of the following examples you may first choose to read the section on marginal cost versus full cost.

The simple comparison

As the original asserion was around greenness my first port of call was Travelfootprint [2] where it is claimed that you can calculate the cost per person of CO2 for different journeys by different means based on full cost. I haven't yet investigated the arithmetic behind their numbers, which one should do later. My first comparison was car versus train London to Manchester. I was assuming a largish petrol car with one passenger versus a 225 electric at 25% utilisation. The journey plotted would have to be somewhat artificial being station to station. The results were

Car - 336.2 km, Average large family petrol, Driver plus 1 passenger, From: London, UK, To: Manchester, Lancashire, UK, Distance: 336.2 km, Lifecycle CO2: 53.3 kg per passenger

Rail - 290.8 km, InterCity 225: electric (national network), 25% occupancy, From: London, To: Manchester, Distance: 290.8 km, Lifecycle CO2: 20.5 kg per passenger

So on that simple (too simple perhaps) comparison the train is at least twice as good. That is not the whole story because in practice I don't live by a London station and I wanted to get to High Lane Stockport. However [3] the figures in this and most other such tables do not represent the real picture. The train doesn't go from your home to your destination - you have to get a taxi, tube or walk or drive to and from the train, all of which lengthens the kilometres and adds pollution. Then you have to take into account the energy overhead to maintain and utilise according to the kilometres travelled. You get in your car and go; trains have to be brought from their garages to the start of their journey (possibly left with engines endlessly idling), so do the driver, conductor, cleaners, ticket issuers, signal-men, safety-staff, announcers, etc etc. Add in all the energy of these "chauffeurs" and the answer may well be different. That is the next calculation.

Applicability

One of the problems of doing this simple analysis is that it is just looking at one metric such as CO2 emmisions. It isn't for example looking at journeys times, or feasibility. For example [5] the London commuter network could never be replaced by roads and cars (and loads more buses are only 'trains' after all). No other city in the UK has a proper commuter network (maybe Manchester, but certainly not the West Midlands). The CO2 saving putting more cars and buses on more roads would be completely wiped out for many years by the CO2 generated building the extra roads. The real debate is not one mode being greener than another, but what's appropriate for the journey, and hence looking at multiple metrics.

Other research

I also had a look at the Future of Mobility Roadmap, [1] whitepaper produced by University of Oxford, Smith School of Enterprise and the Environment. Figure 2.4 page 26 compares Rail to compact car and comes up with a ratio of about 5:1 in favour of the train. Why is that so different to the Travel print results, what different assumptions were made?

References:

[1] Future of Mobility Roadmap, Ways to Reduce Emissions While Keeping Mobile, University of Oxford, Smith School of Enterprise and the Environment, Hayes House, 75 George Street, Oxford OX1 2BQ

[2] The Travelfootprint tool is a Camden and Clear Zones project that is intended for use by the general public, business users and policy makers to compare the life cycle environmental impacts of the main methods of passenger travel in the United Kingdom.
[3] Tony Wright. (with some modifications).

[4] http://epp.eurostat.ec.europa.eu/tgm/table.do?tab=table&init=1&plugin=1&language=en&pcode=tsdtr210 This is data on the percentage of travel currently travelled by various methods in the member countries of the european union. This is a historic statement of the way things are not what the future should be.

[5] Peter Murchison. (with some modifications.

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