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.

Link-based Internal and Full Cost Analysis

Full cost of travel on the Twin Cities Road Network ($/veh-km)

Recent working paper:

This paper develops a link-based full cost model, which identifies the key cost components of travel, including both internal and external versions of cost, and gives a link-based cost estimate. The key cost components for travelers are categorized as time cost, emission cost, crash cost, user monetary cost, and infrastructure cost. Selecting the Minneapolis – St. Paul (Twin Cities) Metropolitan region as the study area, the estimates show that the average full cost of travel is $0.68/veh-km, in which the time and user monetary costs account for approximately 85% of the total. Except for the infrastructure cost, highways are more cost-effective than other surface roadways considering all the other cost components, as well as the internal and full costs.

The Future of Transport and Access

I had the opportunity to present in Manly earlier today to GPT, an Australian property company,   about The Future of Transport and Access. (I also had the opportunity to ride the Manly Fast Ferry, twice!) Actually, I gave the talk 4 times to 4 different groups, as they had the attendees shop around at the marketplace of ideas (it was a regulated marketplace). They had an artist draw my talk (once), which is below.

FutureOfTransportAndAccess

The full book is available of course at a very reasonable price.

The End of Traffic and the Future of Access: A Roadmap to the New Transport Landscape. By David M. Levinson and Kevin J. Krizek.
The End of Traffic and the Future of Access: A Roadmap to the New Transport Landscape. By David M. Levinson and Kevin J. Krizek.

Accessibility,  Equity, and the Journey-to-Work

Recent working paper:

Inequality in transport provision is an area of growing concern among transport professionals, as it results in low-income individuals travelling at lower speeds while covering smaller distances. Accessibility, the ease of reaching destinations, may hold the key in correcting these inequalities through providing a means to evaluate land use and transport interventions. This article examines the relationship between accessibility and commuting duration for low-income individuals, compared to the general population, in three major Canadian metropolitan regions, Toronto, Montreal, and Vancouver using multilevel mixed effects statistical models for car and public transport commuters separately. Accessibility measures are generated for jobs and workers both at the origin (home) and the destination (place of work) to account for the impact of competing labor and firms. Our models show that the impacts of accessibility on commuting duration are present and stronger for low-income individuals than for the general population, and the differences in impact are more visible for public transport commuters. The results suggest that low-income individuals have more to gain (in terms of reduced commute time) from increased accessibility to low-income jobs at the origin and to workers at the destination. Similarly, they also have more to lose from increased accessibility to low-income workers at the origin and to low- income jobs at the destination, which are proxies for increased competition. Policies targeting improvements in accessibility to jobs, especially low-income ones, by car and public transport while managing the presence of competition can serve to bridge the inequality gap that exists in commuting behavior.

Disparity of Access: Variations in Transit Service by Race, Ethnicity, Income, and Auto Availability

Percent zero-car household elasticity
Percent zero-car household elasticity

Recent working paper:

This study explores the relationship between transit-based job accessibility and minority races and ethnicities, low- and middle-income households, and carless households at the block group level for the 50 largest by population metropolitan regions in the United States. A log-linear regression model is used to identify inequities in transit-based job accessibility across the US using data collected from the American Community Survey, the Environmental Protection Agency’s Smart Location Database, and the Access Across America database. The intra-metropolitan analyses reveal that accessibility is unevenly distributed across block groups that have different densities of race and levels of income. The differences in accessibility are especially apparent where there are denser pockets with higher percentages of African Americans, Hispanics, low-income households, and zero-car households. The inter-metropolitan analyses show that accessibility is unevenly distributed across metropolitan regions across the US when considering various sociodemographic populations. Different metropolitan regions provide different levels of accessibility for all investigated sociodemographic categories, whether considering racial minorities, levels of income, or car ownership. The results may inform recommendations for equitable transport planning and policy-making.