Wednesday, December 19, 2012

Trip Length Distribution in Chicago

The average trip length (distance) in Chicago, regardless of the trip purpose and mode, is 7.9 miles. Following is the distribution of trip length in Chicago based on the 2007-08 Chicago Household Travel Survey data. There are many micro-trips (super-short trips) recorded in the database. Examples of these micro-trips are the short trips to buy coffee or lunch from a nearby store while at work. You may think of more examples if you just recall your own trips in the last few days.

Beside the super-short trips, the distribution is obviously has a long tail to the right. One interesting point is that 50% of the recorded trips are less than 5 miles.

Two comments:
  • Auto share for these trips (I mean trips of less than 5 miles which comprise 50% of all the trips in Chicago) is more than 60%. I think, 5 miles can be easily traveled with a bicycle. Just imagine for these trips, if people choose to bike instead of driving. This means that about 30% less vehicles will be moving around the city (with single occupancy assumption). 30% less vehicles in Chicago is roughly equivalent to 4 million vehicle-trips (Chicago has about 13 million vehicle-trips in a day [2007 estimation], predicted to be more than 30 millions in 2016).
  • How does trip length change over years? How is it correlated with land use and sprawl? If a city grows in size, does the average trip length increase? How is trip length distribution in Chicago different from other cities? These are some of the questions that I would like to look into in near future.
* UPDATE 1: The average trip distance in the Los Angeles metropolitan area is approximately 13 miles based on the data presented in a SCAG report (Figure 5-3, page 56).

Population density of the Los Angeles metropolitan area: 2,645 /sq. mi (1,025 /km²)
Population density of the Chicago metropolitan area: 1,318 /sq mi (509 /km²)

Although the population density of Chicago is lower than Los Angeles, trip distances are shorter in Chicago, perhaps because of a more mixed-use land development (requires further research).

* UPDATE 2: The average trip distance in the New York City is approximately 8 miles (about 12 miles for Manhattan) based on the data presented in a NYS DOT report (Table 63-b, page 6-12).

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