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Paper

Challenges in Credibly Estimating the Travel Demand Effects of Mobility Services

 
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Publication: Transport Policy
Volume: 103
Pages: 224-235
Publication Date: 2021
Summary:

Mobility services including carsharing and transportation network company (TNC) services have been growing rapidly in North America and around the world. Measuring the effects of these services on traveler behavior is challenging because the results of any such analysis are sensitive to how (1) outcomes are measured and (2) counterfactuals are constructed. The lack of good control groups or randomization of assignment leaves lingering uncertainty over the contributions of selection bias and treatment effects to reported differences in travel behavior between users and non-users of these services. This paper reports on two approaches for measuring the effects of mobility service adoption on travel rate and car ownership. We first tried a pretest-posttest randomized encouragement experiment to deal with the shortcomings of poor control groups. Then, we turned to the approach of self-reported effects based on hypothetical controls to investigate whether variations in survey question presentation could influence respondents’ answers and thus lead to changes in estimated effects. The data to conduct this study came from two sources: a panel survey administered by the authors at the University of Washington (UW), and a survey by Populus Technologies, Inc. (Populus). Various statistical tests were applied to analyze the data, and the results highlight the pivotal role that the research design plays in influencing the outcomes, and manifest the fundamental challenge of establishing credible estimates of the causal effects of adopting mobility services on travel behaviors.

Authors: Dr. Andisheh Ranjbari, Xiao Wen, Fan Qi, Regina R. Clewlow, Don MacKenzie
Recommended Citation:
Xiao Wen, Andisheh Ranjbari, Fan Qi, Regina R. Clewlow, Don MacKenzie. Challenges in credibly estimating the travel demand effects of mobility services. Transport Policy, (103:224-235) 2021. https://doi.org/10.1016/j.tranpol.2021.02.001.
Paper

Developing Design Guidelines for Commercial Vehicle Envelopes on Urban Streets (Paper)

 
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Publication: International Journal of Transport Development and Integration
Volume: 3:02
Pages: 132 - 143
Publication Date: 2019
Summary:

Commercial heavy vehicles using urban curbside loading zones are not typically provided with an envelope, or space adjacent to the vehicle, allocated for loading and unloading activities. While completing loading and unloading activities, couriers are required to walk around the vehicle, extend ramps and handling equipment and maneuver goods; these activities require space around the vehicle. But the unique space needs of delivery trucks are not commonly acknowledged by or incorporated into current urban design practices in either North America or Europe. Because of this lack of a truck envelope, couriers of commercial vehicles are observed using pedestrian pathways and bicycling infrastructure for unloading activities, as well as walking in traffic lanes. These actions put them and other road users in direct conflict and potentially in harm’s way.

This article presents our research to improve our understanding of curb space and delivery needs in urban areas. The research approach involved the observation of delivery operations to determine vehicle type, loading actions, door locations and accessories used. Once common practices had been identified by observing 25 deliveries, simulated loading activities were measured to quantify different types of loading space requirements around commercial vehicles. This resulted in a robust measurement of the operating envelope required to reduce conflicts between truck loading and unloading activities with adjacent pedestrian, bicycle, and motor vehicle activities. From these results, commercial loading zone design recommendations can be developed that will allow our urban street system to operate more efficiently, safely and reliably for all users.

Recommended Citation:
McCormack, Edward, Anne Goodchild, Manali Sheth, and David Hurwitz. Developing Design Guidelines for Commercial Vehicle Envelopes on Urban Streets. International Journal of Transport Development and Integration, 3(2), 132–143. https://doi.org/10.2495/TDI-V3-N2-132-143