Tuesday 21 May 2013

Road crashes and smoothing the flow

As this slide from a 2012 TfL survey shows, drivers on London's main roads are much more likely to report delays due to roadworks than due to road accidents ('collisions', more accurately) - but TfL's own data shows that in reality collisions are a much more significant source of delay.
And while delays due to roadworks have fallen, presumably due to a flurry of TfL measures designed to reduce the number and length of works on main roads, delays due to collisions remain stubbornly high and are now more than twice as large as for roadworks. 

So just as Andrew Gilligan has been selling his cycling strategy as a way to reduce congestion, shouldn't we also be seeing a big push to drastically reduce the number of road crashes as a way to 'smooth the flow'?

Sunday 12 May 2013

History and cycling's mode share in Amsterdam and London

This presentation by RenĂ© Meijer of the City of Amsterdam has a useful chart showing the transport mode split in Amsterdam by the length of the journey.

I've tried to recreate it for London, using data from the London Travel Demand Survey downloaded from TfL's Romulus website*. It's not possible to make an exact comparison, for a few reasons:
  • For London I use data on journey 'stages', which includes things like walking to the bus stop. It's not clear whether the Amsterdam data uses data on stages or on the main mode used for a trip from A to B.
  • The journey distance categories are slightly different between the two cities.
  • I've included motorcycle journeys in the 'car' category in London, but it's not clear whether or how they are counted in Amsterdam.
With those caveats in mind, here's the London chart.
Note, I've tried to use similar colours, so the reason there's lots of red in the Amsterdam chart and hardly any in the London chart is that lots of people cycle in Amsterdam and hardly anyone cycles in London. The difference is huge, and seems to be made up by a mix of more travel by car and by public transport in London for trips of between 0.5 and 10 km.

London's high public transport share for medium-length trips (predominantly bus until for trips of up to 6km and predominantly Underground/DLR thereafter) is striking, and I think a little under-discussed in the debate about growing cycling. We have a pretty wonderful public transport network that competes against cycling both in terms of attracting passengers and, in the case of buses, for road space. Even though there is definitely scope for huge growth in cycling with the right policies in place, this starting point probably means we're unlikely to match Amsterdam's modal share even for trips of the same length. Cities can't choose their history, and that can make a huge difference to their future.

* You'll need to request a password to access the full site.