Circles represent stations on a standard tube map (includes Overground and DLR). Crosses represent stations that were fully closed during the strike period (source: Larcom et al)

According to a new study of the London Underground, some commuters fail to optimise route and service selection. They take a route that’s not the fastest available to them.

But a major shock like a strike forces them to search out alternative arrangements; in effect to experiment. Some fortuitously discover there’s a better option and make a permanent change.

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Researchers from the universities of Cambridge and Oxford studied a strike in February 2014 that closed 171 of the London Underground’s 270 stations. (1)

They examined travel patterns before and after the strike, using 20 days of anonymised Oyster card data on AM peak travel. Their approach was to compare the travel behaviour of those whose routes were impeded by stations closures – around three quarters of all Tube users – with those who weren’t affected directly.

We estimate that a significant fraction of commuters on the London underground do not travel their optimal route. Consequently, a tube strike (which forced many commuters to experiment with new routes) taught commuters about the existence of superior journeys, bringing about lasting changes in behavior.

The explanation for the sub-optimal behaviour isn’t high search costs. Rather, the researchers attribute it to travellers under-estimating the value of experimentation.

Around one in 20 travellers who changed route decided to stick with it after the strike was over. That might sound small but the time gains these travellers collectively made by improving their journeys was larger than the total time lost by all commuters during the strike.

It therefore appears that the tube network was operating so far away from its optimum that the February 2014 strike managed to improve efficiency of the system as a whole….

The researchers also found that sub-optimal travel choice was most prevalent amongst travellers who live in parts of London where the standard subway map distorts the real geography of the rail system.

London’s highly stylised 1933 tube map is famed for its legibility despite – or more probably because – the correlation between mapped length and actual length is low; just 0.22.

It is a schematic transit map, showing only relative positions of tube and train stations along lines. Consequently, the map is geographically distorted and gives users false impressions when it comes to actual distances between two points, especially when comparing points along different tube/train lines.

For example, Covent Garden and Leicester Square are only 260 meters apart, but the 20 second tube ride is in high demand. Also, the map doesn’t show that trains travel on average three times faster on some lines than on others e.g. Waterloo & City vs Hammersmith & City.

I expect the more spartan rail systems in Australian cities mean sub-optimal route choices by train are less common than in London.

However I suspect there are travellers whose situation would be improved if they had a better understanding of the options offered by buses, either alone or in combination with trains. Even with smartphone apps, the legibility of bus services remains a serious problem.

Similarly, there are others who, if they experimented, would discover that cycling makes better sense for them than their existing mode, whether that be driving or public transport.

Melbourne’s current spate of tram and train strikes has a negative effect on productivity, but it’s undoubtedly prompting more travellers to give Uber a go.

There are a number of other implications of this research. First, it shows that travellers adapt to changed circumstances; the net effect of a change has to be assessed after allowing for adjustment.

Second, not all travellers optimise their route and mode choice; in the absence of change they “satisfice” rather than maximise. The outcome might not be optimal for the system as a whole.

And third, changing behaviour requires more than the mere availability of information; for example, getting travellers to recognise that a bus might be a better option requires finding a way to provide the sort of legibility characteristic of rail-based systems.

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  1. The Benefits of Forced Experimentation: Striking Evidence from the London Underground Network, Shaun Larcom, Ferdinand Rauch and Tim Willems.

    What the London rail system really looks like