Access to Destinations Data

Many years ago, we completed a project called Access to Destinations. The data from the project has been sitting on my hard drive for many years. I am happy that some of it is now preserved for posterity and open science by the University of Minnesota Data Conservancy. See:

 

Unfortunately, due to small methodological changes, these data are not directly comparable with more recent outputs, and the 1995 – 2005 data are really not directly comparable with the 2010 data either. It nevertheless might be interesting for selected applications.

Map Monday: Isochrones and the Thirty-Minute City | WalkSydney

I wrote a thing for WalkSydney: Map Monday: Isochrones and the Thirty-Minute City

Travel Time Platform is a website that lets users draw Isochrones, areas which can be reached in a given amount of time (Iso from the Greek for same, chronos for time). I have used it to draw a time radius. Here we show a 30 minute walking time from the Seymour Centre (near the WalkSydney world headquarters, but you can choose anywhere.)

The 30 minute city is a concept about accessibility, can the important places travelers want to go be reached in a given time. The idea that 70% of the people can reach daily activities within 30 minutes of walk, bike, or transit is embedded in the most recent Metropolis of Three Cities plan of the Greater Sydney Commission.

Isochrone by car. A car will get you farther than walking, biking, or transit in 30 minutes.
Isochrone by car. A car will get you farther than walking, biking, or transit in 30 minutes.

 

How more development can lead to less travel: Examples

Balancing housing and jobs, so that they are located near each other, logically reduces travel compared to a situation where those same jobs are far apart. This has long been understood in the transport planning community (see e.g. Cervero 1989, or my 1998 paper), but is not well grasped among the general public.

However, moving a fixed number of things around is not how cities actually grow. Telling place A you taking away their employment is controversial. More generally new things are added.

Development in Mascot. Photo by author.
Development in Mascot. Photo by author.

It is commonly asserted that more development adds to congestion. And often this is true. But not always, it depends on the type of development. More housing in a housing-rich and job-poor area will result in more total travel. More employment in a job-rich, housing poor area will do similarly. More housing in a job-rich area, and more jobs in a housing-rich area can actually reduce travel.

For our baseline case, imagine a city with two precincts separated by 2 km.

Precinct A: 1000 Jobs, 0 Resident Workers

Precinct B: 0 Jobs, 1000 Resident Workers.

The one-way (morning commute) trip table looks like:

Jobs 1000 0
Workers A B
0 A 0 0
1000 B 1000 0

Total daily travel to work is 2000 person km per day. (Everyone commutes from B to A). Travel on Link BA is 1000 at 2 km per trip, or 2000 person km traveled. (This just analyzes one-way trips. Round trip commutes would double this.)

Case 1. 

There is a proposal to intensify development in Precincts A and B, so each is more locally balanced.

Precinct A: 1000 Jobs, 500 Resident Workers

Precinct B: 500 Jobs, 1000 Resident Workers.

The new one-way (morning commute) trip table looks like (rounded):

Jobs 1000 500
Workers A B
500 A 498 2
1000 B 503 497
  • assuming 0.5 km intrazonal travel distance, using a doubly-constrained gravity model with a d_{ij}(-2) impedance function.

The Daily Travel on links:

AB = 2 @ 2 km

BA = 503 @ 2 km

within A = 498 @ 0.5 km (walking)

within B = 497 @ 0.5 km

TOTAL = 1507 pkt.

This is considerably less than the baseline case as many more travelers can reach their destinations locally. While there is still some commuting, it is far less than before.

Case 2.

There is a proposal to build a locally-balanced Precinct C halfway between Precincts A and B.

Precinct C has 500 Jobs and 500 Workers

The new one-way (morning commute) trip table looks like:

Jobs 1000 0 500
Workers A B C
0 A 0 0 0
1000 B 666.666667 0 333.333333
500 C 333.333333 0 166.666667
  • assuming 0.5 km intrazonal travel distance, using a doubly-constrained gravity model with a d_{ij}(-2) impedance function.

The Daily Travel on links:

BC = BA + BC = 1000 @ 1 km

CA = BA + CA = 1000 @ 1 km

within C = 166 trips @ 0.5 km

TOTAL = 2083 pkt.

In this example, the total person kilometers traveled (pkt) on the links connecting inter-city precincts is essentially identical to the base case, despite adding 500 residents and 500 workers halfway between each. There are an additional 167 pkt daily on the intrazonal market (within C), which is likely walking.

The total one-way commute travel per person however drops, from 2 km/person per day to about 1.38 km/person per day. The average trip length is reduced. The experienced travel is thus about one-third lower.

Case 3

Building on Case 1, completely balancing A and B (so each has 1000 jobs and 1000 workers) reduces one-way commutes further (to 1176 pkt)

The new one-way (morning commute) trip table looks like (rounded):

Jobs 1000 1000
Workers A B
1000 A 941 59
1000 B 59 941
  • assuming 0.5 km intrazonal travel distance, using a doubly-constrained gravity model with a d_{ij}(-2) impedance function.

So, it should be clear from this example that adding development can actually reduce total travel, if it is the right kind of development in the right places.

Transport Accessibility Manual Working Group

I am pleased to announce that the Transportation Research Board Annual Meeting will host the first in-person meeting of the Transport Accessibility Manual Working Group.

 

Transport Accessibility Manual Working Group

Monday 6:00 PM- 7:30 PM
Marriott Marquis, Mint (M4)

David Levinson, University of Sydney, presiding

Sponsored by:

Standing Committee on Bus Transit Systems (AP050)

One of the key problems is what to value when investing in transport or regulating land development. Accessibility — the ease of reaching valued destinations — connects transport and land use, considering both how easy it is to move and where things are located. While many planners know how to measure this, many don’t, and all could benefit from standardizing application to best practice. To that end, a working group would develop such a standard, which would clarify topics like how to measure, how to compute, how to present, and what to consider in terms of accessibility.

 

 

If you are interested in participating, please email me.

Full cost accessibility

Recently published:

Traditional accessibility evaluation fails to fully capture the travel costs, especially the external costs, of travel. This study develops a full cost accessibility (FCA) framework by combining the internal and external cost components of travel time, safety, emissions, and money. The example illustrated compares FCA by automobile and bicycle on a toy network to demonstrate the potential and practicality of applying the FCA framework on real networks. This method provides an efficient evaluation tool for transport planning projects.

Full Cost Access
Full Cost Access

Network Structure and the Journey to Work: An Intra-Metropolitan Analysis

Recently published:
Variation of estimated network measures by Minor Civil Division.
This research quantifies the variation of network structure within the Minneapolis – St. Paul metropolitan area and relates it to average travel time to work for each Minor Civil Division (MCD) in the metro area. The variation of these measures within the metropolitan area is analyzed spatially. The measures of network structure are then related to observed travel. Better connected networks have lower average travel times, all else equal. The results corroborate a relation between network structure and travel and point to the importance of understanding the underlying street network structure.

Measuring polycentricity via network flows, spatial interaction, and percolation

Recent working paper:

Polycentricity is most commonly measured by location-based metrics (e.g. employment density or total number of workers, above a threshold, used to count the number of centres). While these metrics are good indicators of location ‘centricity’, the results are sensitive to threshold-choice. We consider here the alternate idea that a centre’s status depends on which other locations it is con- nected to in terms of trip inflows and outflows: this is inherently a network rather than a location idea. A set of flow and network-based centricity metrics for measuring metropolitan area poly- centricity using Journey-To-Work (JTW) data are presented: (a) trip-based, (b) density-based, and, (c) accessibility-based. Using these measures, polycentricity is computed and rank-centricity distributions are plotted to test whether these distributions follow Zipf-like or Chirstaller-like distributions. Further, a percolation theory framework is proposed for the full origin-destination (OD) matrix, where trip flows are used as a thresholding parameter to count the number of sub-centres. It is found that trip flows prove to be an effective measure to count and hierarchically organise metropolitan area sub-centres, and provide one way of dealing with the arbitrariness of defining a threshold on numbers of employed persons, employment density, or centricities to count sub-centres. These measures demonstrated on data from the Greater Sydney region show that the trip flow-based threshold and network centricities help to characterize polycentricity more robustly than the traditional number or density-based thresholds alone and provide unexpected insights into the connections between land use, transport, and urban structure.SankeyFlowsSydney

Travel Cost and Dropout from Secondary Schools in Nepal

Recent working paper:

Distribution of one-way travel time to lower secondary and secondary public schools in Nepal. Children enrolled vs. children dropped out.
Distribution of one-way travel time to lower secondary and secondary public schools in Nepal. Children enrolled vs. children dropped out.

The study relates the association between travel time to the lower secondary and secondary public schools of Nepal and the dropout grade before leaving secondary school using an ordered logit model. It is shown that as the travel time to the school increases, students are more likely to dropout from the school system in earlier grades. The results from this study will be useful to policymakers, especially from developing countries, as it places transport in the context of education.

Optimum Stop Spacing for Accessibility

Relationship between Dwell Time, Stop Spacing, and Accessibility

Recent working paper:

This paper describes the connection between stop spacing and person-weighted accessibility for a transit route. Population distribution is assumed to be uniform along the line, but at each station, demand drops with distance from the station. The study reveals that neither short nor excessive stop spacings are efficient in providing accessibility. For the configuration of each transit route, an optimum stop spacing exists that maximizes accessibility. Parameters including transit vehicle acceleration, deceleration, top speed, dwell time, and pedestrian walking speed affect level of accessibility achiev- able, and differ in their effect on accessibility results. The findings provide an anchor of reference both for the planning of future transit systems, and for transit operators to make operational changes to system design parameters that improve accessibility in a cost-effective manner. The study technically justifies the “rule of thumb” in setting different stop spacings for metro, streetcars, and other different transit services. Different types of transit vary in their ability to provide accessibility, slower moving streetcar (tram) type urban rails are inherently disadvantaged in that respect. Thus the type of transit service to be built should be of particular concern, if the transit is to effectively serve its intended population.