Comments on: Traffic congestion datapoints of the day A slice of lime in the soda Sun, 26 Oct 2014 19:05:02 +0000 hourly 1 By: BarryKelly Wed, 11 Jul 2012 11:41:10 +0000 I live in London. I’ve said it before, and I’ll say it again: scooters are the way to go. More practical for longer distances, and with filtering, excellent in cities. I effectively don’t experience any congestion at all in London. You have to live quite a long ways out, and positioned right beside stations on either end of your trip, for any rail-based public transport to be remotely competitive. Trips that take an hour+ owing to bus to and from tube station at one end normally take less than 30 minutes, and the primary thing slowing you down is red lights.

@JustinCormack: I can’t speak for Copenhagen, but central Amsterdam is very small and doesn’t really accommodate cars at all. Probably the traffic flow is structurally different – if you draw straight lines between start and finish, I’d bet fewer would cross in Amsterdam.

By: JustinCormack Wed, 11 Jul 2012 09:54:53 +0000 Interesting that Amsterdam and Copenhagen, which have very heavy bike use, are significantly lower than many other more car centric European cities.

By: JCortright Wed, 11 Jul 2012 06:20:22 +0000 Felix:

I hope when you meet with the folks at Tom Tom, that you will ask them why their estimates of the congestion index differ substantially from the estimates produced by Inrix.

Inrix, as you may know, uses GPS data from commercial fleets, about 2 million vehicles in all, to monitor travel times on urban highways throughout the US. They compute a travel time index (the ratio of travel times at congested v. uncongested periods). When I compare the Inrix estimates of the travel time index for the same 20 US cities included in the TomTom index, I get a very modest correlation of .48 (R2). In theory, they are measuring exactly the same thing.

If this sort of data is to be useful, we ought to know who is measuring it accurately, or more generally, what seems to be driving the results we observe in different metro areas.

Also, I would hasten to add that the travel time index is a lousy measure of congestion and travel burdens in different metro areas. It only makes sense if you assume (heroically, inaccurately) that trip distances are equal across metro areas.

I’ve spent a good deal of time trying to debunk the use of these travel time indexes as a basis for making inter-metropolitan comparisons of urban transportation system performance: see my paper for CEOs for Cities at

Briefly, if you ignore travel distances, you are implicitly saying that sprawling metros with very long travel distances have less of a congestion problem because a smaller proportion of travel time is due to the difference in congestion, notwithstanding the fact that people in these sprawling metros (Houston, Atlanta, Nashville) are driving dramatically longer distances, on average. There’s an inherent structural bias in the travel time index that makes it appear that denser, more compact metro areas with shorter average travel distances have a “worse’ congestion problem, when in fact, their residents may actually spend less time traveling.

Happy to provide my comparison of Inrix and Tom Tom travel time indices for 20 US metros at your request.


By: realist50 Wed, 11 Jul 2012 04:42:57 +0000 A couple thoughts in the form of questions and hypotheses:

(1) Could the congestion variations in Edmonton and New York be due to annual variations in weather, specifically the number of days with heavy snow or heavy rain? Alternately, perhaps a major road construction project had caused or exacerbated a bottleneck on a major highway, and was completed at some point during this period? (I’m fairly certain that wasn’t the case for NYC, not sure for Edmonton). FWIW, Edmonton has been completing some significant transportation projects over the past couple years – opened a 3.3 mile light rail extension in April 2010, and opened a 13 mile segment of its ring road in November 2011 ( ID=/acn/201111/31460601616BE-98B3-C30F-0 E83C7914578B71B.html).

(2) Does the Europe versus U.S. comparison imply that it will take European levels of congestion to make U.S. commuters use mass transit systems to anything like the same extent that Europeans do? I wonder because my sense, admittedly anecdotal, is that much of the support for expanding rail systems in relatively “new” U.S. cities (e.g., cities like Dallas-Ft. Worth, Denver, Houston, and Atlanta that were designed for car travel) is driven by people thinking, “I personally won’t use that system much, but it sure will be great because other people will and my commute in my car will then be easier.”

By: fuller.brandon Tue, 10 Jul 2012 17:40:32 +0000 Re: congestion charges – Bloomberg’s proposal was for Manhattan but TomTom’s data spans most of the TriState area. It would be interesting to see how congestion in NYC’s CBD compares to congestion within the congestion charge zones in cities like London, Stockholm, and Singapore.